peer review history article details title …page 1, line 6: the word ‘still’ is not necessary....

PEER REVIEW HISTORY

BMJ Open publishes all reviews undertaken for accepted manuscripts. Reviewers are asked to

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reproduced where possible.

ARTICLE DETAILS

TITLE (PROVISIONAL) HEALTH CARE CONSULTATION AND SICK LEAVE BEFORE AND

AFTER NECK INJURY: A COHORT STUDY WITH MATCHED

POPULATION-BASED REFERENCES

AUTHORS Englund, Martin; Jöud, Anna; Stjerna, Johanna; Malmström, Eva-Maj; Westergren, Hans; Petersson, Ingemar

VERSION 1 - REVIEW

REVIEWER Lena Holm, IMM, Division of Epidemiology Karolinska Institutet. Stockholm I declare I have no competing interests in this manuscript

REVIEW RETURNED 22-May-2013

THE STUDY Item nr 3 and 6 needs to be clarified more, see attached review document. The statistical methods also need further calrfication and possible also some changes.

RESULTS & CONCLUSIONS Is the message clear? Overstaded, but could easliy be corrected

GENERAL COMMENTS OVERALL

A well design study and well written manuscript with interesting

findings and new knowledge. However, I have some key

suggestions and comments.

KEY MESSAGE

The third bullet point is not well supported by the aim or the results

of the study. How could consultation history be important to consider

in tailoring treatment and rehab? I.e. what should be done

differently in patients with previous health care consolations

compare to patients without previous health care consultations?

Further, health care consultations is a marker for ill-health, thus a

thorough medical history is probably more relevant than the

consultation history

ABSTRACT

Participants: The inclusion criteria; age (18 years or older) could

preferable be included in the abstract.

Results: Last sentence; Add information about if it is pre-, post- or

all sick leave

Conclusions The last part of the conclusions is not well supported

on April 7, 2020 by guest. P

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by the aim or the results of the study. How could consultation history

be important to consider in tailoring treatment and rehab? I.e. what

should be done differently in patients with previous health care

consolations compare to patients without previous health care

consultations? Further, health care consultations is a marker for ill-

health, thus a thorough medical history is probably more relevant

than the consultation history

Instead, the conclusions about sick leave should be stated, since it

was one of the aims of the study

INTRODUCTION

Pp5; Line 7 . Ref 1 is s partly supporting the sentence, but the

sentence should preferable be re-written, since approx. 50% of WAD

occurred in impact directions other than rear-end.

Pp 5 Line 27: Reference 15 does not support the sentence about the

prevalence of psychological problems following whiplash trauma.

Pp5 Line 42. “Trauma related factors” may better be replaced with

post- collision health factors since it is not always obvious that the

conditions are related to the trauma. The two references (2 and 3)

are not optima. Ref 2 concerns acute WAD whereas Ref 3, refers to

animal models and hypothesis. If re 3 is used, the sentence should

point this out.

Pp 5. Line 51: Neck pain intensity, cervical range of motion etc. are

not necessarily trauma related. And the studies refereed to have not

always measured these factors directly after the trauma, but rather

with in the first few days or weeks after the collision.

Pp6: Line 16: the objectives of the study….. before and after

diagnosis of distortion of the cervical spine

MATERIAL AND METHODS

Pp 6. Line 53. Please specify which version of ICD.10 that was used

for the periods.

The ICD codes T91.8 A and T91.9. Sequelae of injuries (also called

late whiplash) are not mentioned. 1) These should be included in the

exclusion criteria for identification of both cases and references.

They should also be included in the definition of the outcome (post-

collision) with respect to health care consultations.

Pp8: line 23/24. You write that you match the reference subjects

based on among others “study period” It is unclear what you mean

Pp 9. Outcomes, The categorization into low-frequent, frequent and

high frequent consultation is not optimal. First, it is the labeling

(wording) . It may be better if they are with the actual categorization

instead (0-1 etc)

If you cannot analyze the number of consultations as a continuous



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variable, which would be the optimal way, at least a crude sensitivity

analysis should be reported, where you test various cut-offs. It

would also be more informative if the cut-offs are based on

consensus instead of a statistical cut-off. ( eg. 0-1, 2-4 per year

more than 4.. The main problem with the current categorization is

that the middle category covers 2- 8 consultations, and constitutes a

heterogeneous group with respect to consultations.

Pp10: Sick leave: A more appropriate legend would be work

disability. Furthermore, there is a need for a brief explanation of the

difference between sick leave and disability pension in the Swedish

Social Insurance system (according to the regulations at the time of

your study). Figure 6 only covers 2 years before and 2 years after

the time of diagnose. This is not explained in the methods and why

not 3 years?

RESULTS

Make sure that you write the p in p-value either with uppercase letter

as in the abstract OR lowercase letter (preferable) as in the Results

Section, not both

Pp 11. Line 39. How is “acute” visit in primary care ascertained and

defined? Is it acute or is it sub-acute? Have you any information

about day of collusion? If not, it may be difficult to determine

whether it is an acute visit or not?

Pp 12 Line 17-38. It value that you have compared the low-frequent

user and their transition into high-frequent user. However collapsing

low-frequent and frequent consulters in the following results is a less

good. These results are partly dependent on (influenced by) the first

since low-frequent users constitute more than third of the collapsed

group. I suggest that you isolate the “frequent group” , compare It to

high-frequent users and present these results instead of the results

from the collapsed groups.

Pp 15. Table 3. Preferable add information about the variance

within groups. Can you comment on the results of the high-frequent

group, with respect to the mean increase in number of consultations

especially concerning psychological distress? ( you do so in the

discussion but may well be reported in the Result Section)

Pp 16 line 5. Replace the legend Sick leave, with Work disability

Pp 16 line 7. This is not a case cohort study .It is better to phrase the

first sentence “…….. , 96 subjects of the cases (6.7%) were on…..”

DISCUSSION

PP18 Line: 15 I suggest a rephrasing of the sentence starting

with…Noteworthy, ….” .in average about 16% developed a high-

frequent consultation pattern that may be attributed to the injury. (

The results do not support your statement that this 16% persisted

over at least 3 years… You have calculated the mean over time

(after injury but the curves in figure 5 shows a decrease after year 1



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after the diagnosis.)

Pp18. Line 17. You state: “However in a sub group of patients, high

level of health care consultations were noted already long before the

neck injury diagnosis. This implies that a individually tailored

multimodal rehabilitation is and important tool in the care and

recovery process of a subset of patients after neck injury” None of

the references cited (17, 22) really support this. On the contrary, if

any, there are some evidence that multidisciplinary rehabilitation do

not have an effect on recovery following WAD. Cassidy, J. D., L. J.

Carroll, et al. (2007). "Does Multidisciplinary Rehabilitation Benefit

Whiplash Recovery?: Results of a Population-Based Incidence

Cohort Study." Spine. Now, the study by Cassidy et al , did not

specifically investigate the sub group of patients with massive health

care consumption prior to an injury.

Pp 19 Line: 7-12..In reference 23,ONE possible reason for

depression as a risk factor for WAD, may be an increased risk of

collision due to the pre-collision mental conditions (poor

concentration). However in the next sentence in that paper, the

authors state that poor concentration is not likely to play a role in

rear-end collisions. The way reference 23 is cited in your study is

not completely correct.

FIGURES

Figure 5: Should be labeled months ( not month).. There is no

explanation why you started 3 months prior to the diagnosis of neck

injury and not 36 months as stated in the Method section

REVIEWER Jordan Miller, School of Rehabilitation Science, McMaster University, Hamilton, Ontario, Canada

REVIEW RETURNED 15-Jun-2013

THE STUDY Overall the study was well written, however, the manuscript would be strengthened by converting the use of the term 'neck injured individuals' to 'people with a neck injury' in order to use 'people first language'. Page 1, Line 6: The word ‘still’ is not necessary. Page 1, Line 8: “Tearing of” should be replaced with “injury to”. There are many types of forces present in a whiplash injury, “tearing” implies shear and traction force, but I there are more possible explanations than tissue tearing. Page 1 Line 15: “pain sensitization” needs definition. Perhaps this would be better stated as sensory hypersensitivity and if this statement is made, I think elaboration of tis prognostic indicator is needed (ex: pain pressure, cold hyperalgesia, locally vs. distally) L40-42: You describe prognostic indicators present before trauma and prognostic indicators at the time of trauma, but are there also post trauma prognostic indicators?



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, Line 50: Typographical error: 'rang sum' In the discussion, the classification of the neck injury using S13 was discussed as a potential limitation. I think this is an important part of the discussion that should be elaborated upon. i) In the introduction, the reader is led to think that people who's diagnosis is provided as S13 are primarily whiplash injuries. Is there evidence suggesting this is how whiplash injuries are coded? ii) Is 'sprain or strain' of the neck the most appropriate description of a traumatic neck injury. iii) In the ICD-10 CA WAD 1-3 are classified as S1340-S1342. Were these classifications not available for the physicians who are making the diagnosis? iv) Why was the analysis performed on S13 and S16, S130, S142, etc. were not included? This is not meant to criticize the decision to use only this classification, but I think it is important that the reader understand the rationale for the decision. Also, if S13 is being used to try to target traumatic neck injuries with a whiplash mechanism, sufficient evidence is needed to suggest that S13 is made up of primarily whiplash injuries. Otherwise, this may need to be reframed to suggest the population represents 'people who were diagnosed by their physician as having a sprain or strain of the neck.

REVIEWER Daniel Pinto Assistant Professor, Department of Physical Therapy and Human Movement Sciences/Center for Healthcare Studies, Feinberg School of Medicine, Northwestern University USA I have no competing interest

REVIEW RETURNED 27-Jun-2013

THE STUDY Description of methods: There could be a more precise reporting of methods which would specific in greater detail which statistical tests were performed with a given variable. All of the statistical tests were reported but it would have been helpful to know whether in a given situation the researchers were comparing count data versus proportions. Also, it was unclear whether there was justification for use of t-tests with count data. This would require that a large number of levels were present in the data.

RESULTS & CONCLUSIONS the results section is lacking organization The conclusion that consultation history be taken into account when tailoring individual treatment seems premature considering there was no discussion about how this might happen. In fact, the study doesn't discuss optimal health care use at all which may fall somewhere between the low users and high users.

GENERAL COMMENTS They used four matched controls per case with sensitivity analyses based on matched variables. However, this paper makes for difficult reading on account of poor organization and a lack of clarity concerning methodology. Specific comments: Pages 2-3 Abstract:



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Objectives: could introduce rationale from line 1 page 4 into objectives in abstract providing reader with context of study. Conclusions: It is not clear how consultation history should be taken into account. Unless authors propose some suggestions as to how this might be realized, I suggest this statement be altered. Page 4 Article summary: Strengths and limitations: Potential misclassification – bias toward showing less difference between groups . . . This was not well discussed in the limitations section of the article. How do the authors suggest this might produce this bias? This requires further explanation in the discussion section to earn inclusion in the summary. Page 5, Introduction, top of the page, line 0 – the sentence beginning with “the so called whiplash . . .” Are the authors specifically speaking of injuries to soft tissue structures? If so, for clarification it is suggested that the words ‘soft tissue’ be inserted between ‘several’ and ‘structures’ in the sentence. Additionally, the word ‘capsule’ following ‘facet joint’ is suggested. Page 5, line 37. The sentence beginning with “Recent studies have reported . . .” is introducing the relationship with pre-injury consultation rate and post-injury utilization. This is further developed in the paragraph beginning on the top of page 6 and it is suggested that this sentence be moved to the beginning of the paragraph on page 6. Methods: It was confusing that sick leave was captured only for two years post injury and the rest three years post injury. In part, changing the location at which this information is presented in the methods section may alleviate this. Sick leave timeframe is located in the ‘data sources’ subsection and the follow-up of the subjects was reported in the ‘Neck injury cohort’ subsection of ‘Study cohorts’. It is suggested that the sentence “sick leave data was available . . .” on page 7 be moved to page 8 at the end of the Neck injury cohort subsection. Page 7 under neck injury cohort, the sentence starting with “We excluded all cases. . .” It may be clearer to write out the range in years as ‘between 1998 and 2007- up until the month before diagnosis’. Reference cohorts - Is there a reason why reference 3 was not the only cohort included in the study? For example, were there concerns with overmatching? It is suggested that Table 1 be moved to the results section as it includes a description of the cohorts based on educational level. Outcomes: Page 9. Why was two years before injury chosen as the timeframe to categorize patients as low, frequent, or high-frequent users? It seems odd that total information was captured for all participants three years before injury and all of the data was not used to categorize these patients. How might the story change if all of this



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data was used. Statistical analysis – This section could use more clarity in terms of identifying in detail which variables where analyzed with which statistical tools. Why not report Odds Ratios along with attributable risk? Multiple T-tests across subgroups are not typically suggested without error correction, it is suggested that the authors justify this practice. Also, please report that variance was equal across groups and a t-test taking unequal sample size into account was used. Also it appears that there was comparison of count data between groups, subgroups, and years using t-tests or non-parametric tests. This practice should be justified – statistical analysis of count data as continuous is only acceptable if there are sufficient levels to each variable. Otherwise models could be constructed to take confounders into account and it is suggested that the authors consider analyzing the data using a Poisson distribution. Results: This section needs more organization. Please consider organizing according to Cohort characteristics Group results Stratified analyses Diagnoses treated Sick leave Changes over time (referred to in the analysis but not specifically addressed in its own section) Cohort characteristics: For clarity it is suggested that the words, “in an acute, non-planned visit” be added after the word ‘physician’ in the first sentence in this section. Group results Consider reporting how the neck injured consulted as a group relative to the references in the 3 years prior to the injury. It is not surprising that they consulted more over the 6 year period when a major injury took place within this cohort. Top of page 12 first full sentence, starting with “The mean age, . . .” you speak to the neck injured and primary references here but in the next sentence you do not refer to any groups. Is the first sentence differentiated because the secondary references were different? If not, it is suggested that the words, “neck injured and primary references of” be removed from this sentence to improve clarity. Stratified analyses: (If I am understanding correctly the discussion of your stratified analyses starts on page 12, second paragraph) Page 12, second paragraph starting “of the neck injured”. It is suggested that this falls under a different heading as the outcome is not health care consultations per se, but the transition in healthcare user classification. This appears to be an area in which an odds ratio would be suitable. In the methods section outline for the reader that you intend to identify corresponding risk and attributable risk and how this is done. On page 9 you refer to assessing the absolute portion of those injured – please describe how this was done for



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your reader. Page 12, paragraph starting, “In the stratified analyses, . . .” see comments on Changes over time below. Please review your calculation of attributable risk. By plugging in the case-control numbers into an immediate form program in Stata, I obtained an Odds Ratio of 2.47 and attributable risk percentage of 59% for transitioning from a low/medium frequency user to a high frequency user following neck injury. In many respects this is expected in the first year of treatment. I would be interested in a table that reports the odds of transitioning from low frequency to high frequency at each year of follow-up. This nicely supports the introduction that there are a lot of people who are not improving following acute neck injury. Page 14, second sentence beginning with “the proportion of subjects who were classified as low-frequent among neck injured . . .” It appears prior to the injury there was a greater percentage of the neck injured group who were in the low-frequent consulters category 26 v 14% - is this a mistake? How does this fit into the overall message of the paper – that the neck injured consulted more on average than the references? Also this sentence appears misplaced, it is suggested that this sentence would be better placed in page 12 within the paragraph starting, “of the neck injured . . .” Diagnoses treated The content on page 14 can be organized under this heading. Sick leave, Page 16 The sentence starting, “Among the cases . . .”, The mean number of sick days was higher but was this significantly different? Please clarify whether this difference was significant. The percentages reported in table 4 seem close for the low and frequent users. A correlation between sick leave days and health care consultations before injury is expected and not particularly newsworthy. In the final sentence, is the increase in sick days over the two years under study? How did year two look relative to year 1? Perhaps this could be considered in the next section my suggested reorganization is taken. Changes over time There is no specific discussion to changes over time in its own section but it holds so much importance to the message of this paper. It would be fitting to have a section specifically devoted to comparing baseline to Year 1 versus Year 2 versus Year 3. On page 12, the portion starting with, “In the stratified analyses . . . ”. This would be great to move to this section and expand on it here. Discussion: Ultimately it is not surprising that individuals use more medical care following an acute neck injury (at 3-6 months) – in fact, this may be an appropriate use of services. The fact that some low users of healthcare remain low users even after an acute injury may be problematic given the nature of the injuries under study. Might this, in fact, increase the likelihood that chronic pain becomes established? Do we know what they right use of healthcare services is? Perhaps this should be considered as a limitation or a discussion point. These subgroups may be poor representations of identifying what appropriate use might be.



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However, it is interesting that individuals persist as high users of health care in subsequent years, up to year 3. I believe this article is best suited to focus on this in relation to appropriate use. If the conclusion states previous consultation history should be taken into account, how do the authors propose to do this? Via questionnaire at intake? How would management change? In the end you are saying that there are individuals who tend to use our health system differently low, frequent, and high users and this pattern changes slightly post injury. OK, how does this help me as a clinician? Table 3 is very busy and difficult to read. Table 4: I only compared the low-frequent groups on sick leave however, when comparing the proportions in table 4, although odds were increased for sick leave due to neck injury the 95% CI for the odds ratio crossed 0 and the chi square was not significant. By what methodology were significant differences found between these groups? I am assuming you tested the difference in the proportions here. This is where more specific detail is required in the methods section to allow a user to reproduce your results. Figure 4. In this figure it appears that there is also a transition from high to low utilization. This should be discussed as to why this might occur. Figure 5. Are we to assume that -3 months is representative of mean healthcare consultations over the previous 3 year period? Limitations: In addition to other suggested additions, please discuss the limitation associated with having to eliminate diagnoses from private care as noted on page 6 – this will speak to the generalizability of these findings in countries where most of the management occurs in a private system.

VERSION 1 – AUTHOR RESPONSE

Reviewer: Lena Holm,

IMM, Division of Epidemiology Karolinska Institutet. Stockholm

I delcare I have no competing interests in this manuscript

OVERALL

A well design study and well written manuscript with interesting findings and new knowledge.

However, I have some key suggestions and comments.

Authors' reply: We thank the expert reviewer for her positive response to our manuscript, and very

much appreciate the thoughtful input provided.

KEY MESSAGE

The third bullet point is not well supported by the aim or the results of the study. How could

consultation history be important to consider in tailoring treatment and rehab? I.e. what should be



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done differently in patients with previous health care consolations compare to patients without

previous health care consultations? Further, health care consultations is a marker for ill-health, thus a

thorough medical history is probably more relevant than the consultation history

Authors' reply: Thank you for highlighting this. We agree.

Authors' action: We have deleted this implication throughout the manuscript.

ABSTRACT

Participants: The inclusion criteria; age (18 years or older) could preferable be included in the

abstract.

Authors' reply: We agree.

Authors’ action: “aged ≥18” has been inserted under the Participants” subheading in the abstract.

Results: Last sentence; Add information about if it is pre-, post- or all sick leave

Authors' reply: We agree.

Authors’ action: “pre-injury” has been added to the sentence. The sentence now reads: ‘Number of

days of sick leave pre-injury was associated with the number of both pre- and post-injury

consultations (ρ=0.46 99% CI 0.38-0.48, ρ=0.33 99% CI 0.26-0.36).’

Conclusions The last part of the conclusions is not well supported by the aim or the results of the

study. How could consultation history be important to consider in tailoring treatment and rehab? I.e.

what should be done differently in patients with previous health care consolations compare to patients

without previous health care consultations? Further, health care consultations is a marker for ill-

health, thus a thorough medical history is probably more relevant than the consultation history

Instead, the conclusions about sick leave should be stated, since it was one of the aims of the study

Authors’ reply: We have reconsidered that part of the conclusion.

Authors’ action: The last paragraph now reads: ‘Pre-injury levels of sick leave are associated with

both pre-injury and post-injury levels of health care consultations.’

INTRODUCTION

Pp5; Line 7 . Ref 1 is s partly supporting the sentence, but the sentence should preferable be re-

written, since approx. 50% of WAD occurred in impact directions other than rear-end.

Authors’ reply: We thank the reviewer for pointing this out.

Authors’ action: We have in accordance with reviewer 2 deleted the word still in this sentence.

Although, we have chosen to keep this reference on the rear-end collision as a common cause for

neck injury, though we are aware of that other causes also are important. The sentence now reads

line 3: ‘One common cause for trauma resulting in pain and dysfunction of the neck is the rear-impact

car crash.[1]’

Pp 5 Line 27: Reference 15 does not support the sentence about the prevalence of psychological

problems following whiplash trauma.

Authors’ reply: Thank you so much for mention this error, this article does not fit here.

Author’ action: We have deleted this reference from the manuscript (line 12).

Pp5 Line 42. “Trauma related factors” may better be replaced with post- collision health factors since

it is not always obvious that the conditions are related to the trauma. The two references (2 and 3) are

not optima. Ref 2 concerns acute WAD whereas Ref 3, refers to animal models and hypothesis. If re 3

is used, the sentence should point this out.

Authors’ reply: We agree.

Author’ action: We have deleted reference 3 (line 18) since this paper does not necessarily focus on

technical aspects of the injury. We have changed trauma-related factors to post- collision health

factors throughout the manuscript.



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Pp 5. Line 51: Neck pain intensity, cervical range of motion etc. are not necessarily trauma related.

And the studies refereed to have not always measured these factors directly after the trauma, but

rather with in the first few days or weeks after the collision.

Authors’ reply: We thank you for pointing this out.

Authors’ action: We have made changes to clarify that these factors don’t necessarily have to occur in

a narrow time period around the collision. In line with your previous comment, we have changed

terminology, from trauma-related factors to post- collision health factors throughout the manuscript.

Pp6: Line 16: the objectives of the study….. before and after diagnosis of distortion of the cervical

spine

Authors’ reply: Thank you good suggestion on how to make our objective clearer.

Authors’ action: Our objective in the introduction section has now been changed in accordance with

that of the abstract. The sentence now reads (line 8):

‘Hence, the objective was to study health care consultation and sick leave patterns before and after

neck-injury (whiplash).’

MATERIAL AND METHODS

Pp 6. Line 53. Please specify which version of ICD.10 that was used for the periods.

The ICD codes T91.8 A and T91.9. Sequelae of injuries (also called late whiplash) are not mentioned.

1) These should be included in the exclusion criteria for identification of both cases and references.

They should also be included in the definition of the outcome (post-collision) with respect to health

care consultations.

Authors’ reply: Thank you for highlighting these highly important aspects. The Swedish version of

ICD10-SE, was used.

Regarding late whiplash diagnosis; we chose not to exclude people with late whiplash diagnosis,

given that they meet all inclusion criterions. However, only one (1) patients and nine (9) controls had a

late whiplash diagnosis prior to inclusion, none of which was the primary cause for the consultation.

In terms of the definition of outcome, late whiplash injury was included as all other causes for

consultation, not specified. A total of 32 267 diagnoses was registered for the cases in the post-injury

period among these 294 (0.9%) was a ‘late whiplash’ diagnosis T91.8/A and/or T91.9.

Authors’ action: We have clarified the version of ICD-10 in the methods section page 6.

Pp8: line 23/24. You write that you match the reference subjects based on among others “study

period” It is unclear what you mean

Authors reply: Thank you for noting this, this is a mistake (a left over from a previous version).

Authors’ action: We have deleted this part of the sentence. The sentence now reads (line 7): ‘To be

able to compare the health care pattern and sick leave pattern of cases with the general population,

we also assigned each case with four reference subjects randomly sampled from the Swedish

population register matched for birth year, sex and area of residence (figure 1, table 1).’

Pp 9. Outcomes, The categorization into low-frequent, frequent and high frequent consultation is not

optimal. First, it is the labeling (wording) . It may be better if they are with the actual categorization

instead (0-1 etc)

If you cannot analyze the number of consultations as a continuous variable, which would be the

optimal way, at least a crude sensitivity analysis should be reported, where you test various cut-offs. It

would also be more informative if the cut-offs are based on consensus instead of a statistical cut-off. (

eg. 0-1, 2-4 per year more than 4.. The main problem with the current categorization is that the middle

category covers 2- 8 consultations, and constitutes a heterogeneous group with respect to

consultations.



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Authors’ reply: Thank you very much for these comments and suggestions on the cut-offs. We have

thoroughly discussed the terminology within our group and other co-worker and also looked in

published work to find the proper terminology to use. As there are no “gold standard definitions”,

numerous ways of categorizations are possible and it’s a trade-off not having too many subgroups

compare to not having too large heterogenic groups. Still, categorization is often performed to simplify

analysis and presentation; advantages that often outweigh the disadvantages.

In the table below we give you the number of patients and references within each sub-group and the

mean (median) number of consultations per year before and after injury for the patients (based on

cut-offs as suggested by you) and ‘old’ cut-offs used in manuscript. As can be seen although the

actual figures differ a bit whit is expected the overall change within groups is similar.

Pre-injury Post-injury

‘New’ ‘Old’ ‘New’ ‘Old’

Low-frequent (0-1)

n=384 (vs. 384) 1.3 (1.8) 1.3 (1.8) 3.3 (6.3) 3.3 (6.3)

Frequent (2-4)

n=335 (vs. 583) 3.3(4.3) 4.7 (5.5) 6.0 (8.8) 6.7 (9.7)

High-frequent (+4)

n=724 (vs. 476) 11.0 (15.6) 15.3 (20.1) 11.7 (17.8) 15.0 (21.4)

We politely suggest keeping the categorization as is.

Pp10: Sick leave: A more appropriate legend would be work disability. Furthermore, there is a need

for a brief explanation of the difference between sick leave and disability pension in the Swedish

Social Insurance system (according to the regulations at the time of your study). Figure 6 only covers

2 years before and 2 years after the time of diagnose. This is not explained in the methods and why

not 3 years?

Authors’ reply: Thank you for valid suggestion on sick leave-work disability. In the last sentence page

6 paragraph work disability, we mention that we only have work disability data available for all

subjects until 2 year post injury.

Authors’ action: Legends Sick leave has been changed under the Methods section (page 7 line 1 and

page 10 line 10), we now use the term Work disability. We have added more information on sick leave

and disability pension page 10, line 10 and also in accordance with reviewer 3 moved the sentence

where we mention that we only have work disability data up until 2 year post injury to the section’Neck

injury cohort’. We hope this will better clarify our study period with respect to work disability.

RESULTS

Make sure that you write the p in p-value either with uppercase letter as in the abstract OR lowercase

letter (preferable) as in the Results Section, not both

Authors’ action: We agree, all uppercase P have been corrected as appropriate to lowercased p.

Pp 11. Line 39. How is “acute” visit in primary care ascertained and defined? Is it acute or is it sub-

acute? Have you any information about day of collusion? If not, it may be difficult to determine

whether it is an acute visit or not?

Authors’ reply: thanks you for this important question. In the register we can see whether the

consultation was a priori scheduled or not. This is marked in the register as acute=yes/no. We have,

unfortunately, no information on potential collision date.



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Pp 12 Line 17-38. It value that you have compared the low-frequent user and their transition into high-

frequent user. However collapsing low-frequent and frequent consulters in the following results is a

less good. These results are partly dependent on (influenced by) the first since low-frequent users

constitute more than third of the collapsed group. I suggest that you isolate the “frequent group” ,

compare It to high-frequent users and present these results instead of the results from the collapsed

groups.

Authors’ reply: thank you for these suggestions. We agree that this is two groups that don’t

necessarily should be analyzed together especially since the low frequent consulter group is larger

however; we did this because of the low number in totals. When we analyze the frequent group alone

the attributable risk is 17.8%.

Authors’ action: As suggested by reviewer 3, a new table including risk ratios and attributable risks for

transition between groups and year have been added to the results section.

Pp 15. Table 3. Preferable add information about the variance within groups. Can you comment on

the results of the high-frequent group, with respect to the mean increase in number of consultations

especially concerning psychological distress? ( you do so in the discussion but may well be reported

in the Result Section)

Authors’ reply: Thank you for this comment. On Page 15 line 7 we present the result over high

prevalence’s of psychological distress during the whole study period in the high frequent group. This

is also discussed in the discussion section. We politely suggest not extending these sections.

Pp 16 line 5. Replace the legend Sick leave, with Work disability

Authors’ reply: Legend has been changed.

Pp 16 line 7. This is not a case cohort study .It is better to phrase the first sentence “…….. , 96

subjects of the cases (6.7%) were on…..”

Authors’ reply: Thanks you for pointing this out.

Authors’ action: the sentence have been changed, it now reads: ‘At the day of the neck injury

diagnosis, 96 subjects of the cases (6.7%) were on disability pension,…’

DISCUSSION

PP18 Line: 15 I suggest a rephrasing of the sentence starting with…Noteworthy, ….” .in average

about 16% developed a high-frequent consultation pattern that may be attributed to the injury. ( The

results do not support your statement that this 16% persisted over at least 3 years… You have

calculated the mean over time (after injury but the curves in figure 5 shows a decrease after year 1

after the diagnosis.)

Author’s reply: Thank you for this comment; we agree that this sentence should be rephrased in order

to better describe the pattern although the pattern seems to exist three years after injury. Please note,

figure 5 displays the pattern over time stratified by pre-injury consultation level.

Authors’ action: The sentence have been changed and it now reads (page 22, line 4): Noteworthy,

about 16% of the transition from low or frequent consulters pre-injury to high-frequent consultation

pattern the year after diagnosis could be attributed to the injury, and this pattern persisted, although

slightly declining, up to at least 3 years.

i) Pp18. Line 17. You state: “However in a sub group of patients, high level of health care

consultations were noted already long before the neck injury diagnosis. This implies that a individually

tailored multimodal rehabilitation is and important tool in the care and recovery process of a subset of

patients after neck injury” None of the references cited (17, 22) really support this. On the contrary, if

any, there are some evidence that multidisciplinary rehabilitation do not have an effect on recovery

following WAD. Cassidy, J. D., L. J. Carroll, et al. (2007). "Does Multidisciplinary Rehabilitation Benefit



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Whiplash Recovery?: Results of a Population-Based Incidence Cohort Study." Spine. Now, the study

by Cassidy et al , did not specifically investigate the sub group of patients with massive health care

consumption prior to an injury.

Author’s reply: Thank you for this comment and reference. We agree that the literature is not

convincing on whether a multidisciplinary approach is the best, even if this particular article by

Cassidy et al have a prolonged time before rehabilitation start which could be assumed affecting the

results (median days 143). However, our study indicates that the background history of consultation is

a proxy for ill-health. This is an aspect we suggest may be included in the treatment and rehabilitation

of the patients regardless of disease or injury and regardless of type of rehabilitation.

Author’s action: We have chosen to delete the last sentence in the first paragraph under discussion;

since it’s not supported in our results. We have also included the suggested reference.

Pp 19 Line: 7-12..In reference 23,ONE possible reason for depression as a risk factor for WAD, may

be an increased risk of collision due to the pre-collision mental conditions (poor concentration).

However in the next sentence in that paper, the authors state that poor concentration is not likely to

play a role in rear-end collisions. The way reference 23 is cited in your study is not completely correct.

Authors’ reply: Thank you for highlighting this. We believe that this article suggests poor concentration

as a risk factor for car collision in general. Hence, we don’t mean to imply that this would be the case

with rear-ending specifically.

FIGURES

Figure 5: Should be labeled months ( not month).. There is no explanation why you started 3 months

prior to the diagnosis of neck injury and not 36 months as stated in the Method section.

Authors’ reply: Thank you for this question and comments. We wanted to give the reader a possibility

to see the change in months rather than in years in this figure. In order to facilitate this (simply to

make the figure more readable), we started at 3 month before injury.

Authors’ action: “Month” has been changed to “months” and the time-period has now been explained

under the method’s section. The sentence on the stratification on page 9 line 8 now reads: ‘We used

this categorization to perform stratified analyses. We present the numbers per year throughout with

one exception; to study the number of consultations in detail after injury we display mean number of

consultation within each subgroup by quarters of a year starting three months pre-injury.’ We have

also pointed this out in the figure legend.

Reviewer: Jordan Miller, School of Rehabilitation Science, McMaster University, Hamilton, Ontario,

Canada

Overall the study was well written, however, the manuscript would be strengthened by converting the

use of the term 'neck injured individuals' to 'people with a neck injury' in order to use 'people first

language'.

Authors’ response: Thank you for this comment and the valuable suggestion on how to improve the

language. We very much appreciate your expertise and careful input helping us to improve the

manuscript.

Authors’ action: We have changed the wording 'neck injured individuals' to 'people with a neck injury'

throughout the manuscript.

Page 1, Line 6: The word ‘still’ is not necessary.

Authors‘ action: the word ‘still’ has been deleted.



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, Line 8: “Tearing of” should be replaced with “injury to”. There are many types of forces

present in a whiplash injury, “tearing” implies shear and traction force, but I there are more possible

explanations than tissue tearing.

Authors’ action: We agree. The sentence have been rephrased and now read: ‘The so called whiplash

trauma mechanism may result in injury to several structures present in the neck…’

Page 1 Line 15: “pain sensitization” needs definition. Perhaps this would be better stated as sensory

hypersensitivity and if this statement is made, I think elaboration of tis prognostic indicator is needed

(ex: pain pressure, cold hyperalgesia, locally vs. distally)

Authors‘ action: This sentence has been deleted, we found it added little to the introduction.

L40-42: You describe prognostic indicators present before trauma and prognostic indicators at the

time of trauma, but are there also post trauma prognostic indicators?

Authors’ reply: We thank the reviewer for this important and interesting question. We believe there are

post trauma prognostic factors, connected or not connected to the trauma itself. Besides these,

factors like compensation certificates, type of treatment and beliefs have been shown both to improve

and halter the rehabilitation process (Spearing 2012, Cassidy et al. 2007, Carroll et al. 2009)

Authors’ action: In line with reviewer ones (1) comment on the terminology concerning trauma-related

factors this terminology has been changed to ‘post-trauma related health factors’.

Page 10, Line 50: Typographical error: 'rang sum'

Authors’ reply: Thank you for mention this error.

Authors’ action: We have in compliance with reviewer 3 deleted this sentence.

In the discussion, the classification of the neck injury using S13 was discussed as a potential

limitation. I think this is an important part of the discussion that should be elaborated upon.


Authors’ action: We have further elaborated upon the uncertainty of the coding and limitation not

knowing the true cause of the patients’ complaints; please see page 24, row 19.

.

i) In the introduction, the reader is led to think that people who's diagnosis is provided as S13 are

primarily whiplash injuries. Is there evidence suggesting this is how whiplash injuries are coded?

Authors’ reply: Thank you for this important question. We have used the ICD-10 code recommended

to use in relation to a whiplash trauma to the neck. S134 include S134A-C, A=Whiplash injury WAD 1,

B Whiplash injury WAD 2 and Whiplash injury WAD 3. However, we discussed the coding procedures

both with primary care practitioners and with pain specialist and we came to the conclusion that S13.4

should be used in whole since most of the coding still is done without using A-C classification. This is

also what’s been done in previous studies and investigations in Sweden. However, there are other

codes that could be used, late whiplash injury and other like S14.0 Concussion and oedema of

cervical spinal cord, S24.1 Other and unspecified injuries of thoracic spinal cord however these are

not the common codes to use.

ii) Is 'sprain or strain' of the neck the most appropriate description of a traumatic neck injury.

Authors’ reply: We agree that this might not be the best word to use, however this is the wording used

in the international version of ICD10, S13.4.

Authors’ action: We comply with your comment and have changed our terminology to neck injury

throughout. The sentence under subheading neck injury cohort page 7 now reads:

‘We identified all adult (18 years or older) residents of Region Skåne who had been diagnosed with

neck injury, Whiplash, ICD-10-SE code S13.4*’,

iii) In the ICD-10 CA WAD 1-3 are classified as S1340-S1342. Were these classifications not available

for the physicians who are making the diagnosis?



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Authors reply: We thank you for this question. We appreciate that this is not described properly in our

manuscript. In the Swedish version S134 include S134A-C, as the CA version include 0-2, where A-C

equals whiplash injury WAD 1-3.

Author’ action: To better describe the diagnostic codes used in our study we have added information

about how S134 is built up in the Swedish version of ICD-10. We have inserted a new sentence on

this on page 7, line 22 that read:

‘S13.4 is in the Swedish ICD-10 version further subdivided for Whiplash associated disorder (WAD) 1-

3, by the letter A-C (i.e., S13.4A).’ Please see also our reply to i) above.

iv) Why was the analysis performed on S13 and S16, S130, S142, etc. were not included?

This is not meant to criticize the decision to use only this classification, but I think it is important that

the reader understand the rationale for the decision. Also, if S13 is being used to try to target

traumatic neck injuries with a whiplash mechanism, sufficient evidence is needed to suggest that S13

is made up of primarily whiplash injuries. Otherwise, this may need to be reframed to suggest the

population represents 'people who were diagnosed by their physician as having a sprain or strain of

the neck.

Authors’ reply: We were primarily interested in the whiplash injury mechanism, and that is why we

focused on those particular ICD-10 codes. However, due to the observational nature of the study

including some uncertainty of the physicians’ coding practice etc.; we do not know that all patients

have been truly exposed to a whiplash trauma. Hence, we fully agree with the reviewer’s comment,

and hope that this has been accurately conveyed in the limitations section (page 24 lines 19-24).

Reviewer: Daniel Pinto

Assistant Professor, Department of Physical Therapy and Human Movement Sciences/Center for

Healthcare Studies, Feinberg School of Medicine, Northwestern University

USA

I have no competing interest

We thank the expert reviewer for his very helpful input on our manuscript

Description of methods: There could be a more precise reporting of methods which would specific in

greater detail which statistical tests were performed with a given variable. All of the statistical tests

were reported but it would have been helpful to know whether in a given situation the researchers

were comparing count data versus proportions.

Authors’ reply: Thank you for this important comment, we agree that a more precise description would

facilitate for the reader and also that better statistical methods taking the underlying distribution into

account in better ways. Therefore substantial changes have been made concerning the analysis

hence also the statistical analysis section. We have included risk ratios in combination with the

attributable risks, and Jonckheere-Terpstra test when analysing differences between patients with

neck injury to the references. Lastly we have, as suggested, included repeated negative binominal

regression models to study the difference between subgroups taking other variables into account.

Authors’ action: We have updated the whole Statistics analysis section and changed the analysis

accordingly, starting on page 10.

Also, it was unclear whether there was justification for use of t-tests with count data. This would

require that a large number of levels were present in the data.

Author’s reply: thank you for pointing this out. We agree and think this is a valid point.

Authors’ action: We have made major changes regarding our statistics; we now include t-test, Mann-

Whitney U-test and median tests, Jonckheere-Terpstra. We do however correlate number of

consultations with number of sick days; therefore we have added Fischer’s z transformation to

compute 99% CI around the correlation coefficient. This is explained in the statistics section starting



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on page 10.

the results section is lacking organization

Authors’ reply: We appreciate your suggestions (below) and have revised the results section

accordingly.

The conclusion that consultation history be taken into account when tailoring individual treatment

seems premature considering there was no discussion about how this might happen. In fact, the study

doesn't discuss optimal health care use at all which may fall somewhere between the low users and

high users.

Authors’ reply: Thank you for highlighting this aspect. We agree that this part of our conclusion is

premature and agree that the best way at this stage is to delete the sentence.

Authors’ action: The sentence has been deleted.

The authors should be congratulated for their work. They have carried out a well-conducted case-

control design assessing health care consultation and sick leave before and after neck injury. They

used four matched controls per case with sensitivity analyses based on matched variables. However,

this paper makes for difficult reading on account of poor organization and a lack of clarity concerning

methodology.

Authors’ reply: We appreciate you positive comments on our work and are thankful for your questions,

comments and suggestions to help us improve the paper.

Specific comments:

Pages 2-3

Abstract:

Objectives: could introduce rationale from line 1 page 4 into objectives in abstract providing reader

with context of study.

Authors’ reply: Thanks you for this good suggestion.

Authors’ action: Due to word limitations the the objectives in the abstract now read: ‘Recent studies,

based on self-assessed data both on exposure and outcome, suggest a negative association between

poor health before neck injury and recovery. Our aim was to study actual health care consultation and

work disability before and after neck injury (whiplash).’

Conclusions: It is not clear how consultation history should be taken into account. Unless authors

propose some suggestions as to how this might be realized, I suggest this statement be altered.

Authors’ reply: We appreciate this suggestion and agree.

Authors’ action: We have deleted this section.

Page 4

Article summary: Strengths and limitations:

Potential misclassification – bias toward showing less difference between groups . . . This was not

well discussed in the limitations section of the article. How do the authors suggest this might produce

this bias? This requires further explanation in the discussion section to earn inclusion in the summary.

Authors’ reply: Typically non-differential misclassification of an exposure (which we believe is the case

here) will bias estimates towards the null, i.e. making it harder to detect true differences between

groups. With word count in interest we choose not to elaborate on this further in the discussion.

Authors’ action: We have deleted part of the limitations section under the summary, it now reads: ‘A

limitation of the study is potential misclassification of injury although the injury code used to identify

cases primarily is connected to the whiplash injury mechanism; other trauma mechanisms may be

included as well.’

Page 5, Introduction, top of the page, line 0 – the sentence beginning with “the so called whiplash . . .”



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Are the authors specifically speaking of injuries to soft tissue structures? If so, for clarification it is

suggested that the words ‘soft tissue’ be inserted between ‘several’ and ‘structures’ in the sentence.

Additionally, the word ‘capsule’ following ‘facet joint’ is suggested.

Authors’ reply: Yes, we do and agree.

Authors’ action: We have followed your suggestions and added ‘soft tissue’ and capsule as

suggested. The sentences now read: ‘The so called whiplash trauma mechanism may result in injury

to several soft tissue structures present in the neck e.g. facet joints capsule…’

Page 5, line 37. The sentence beginning with “Recent studies have reported . . .” is introducing the

relationship with pre-injury consultation rate and post-injury utilization. This is further developed in the

paragraph beginning on the top of page 6 and it is suggested that this sentence be moved to the

beginning of the paragraph on page 6.

Authors’ reply: Thank you for this comment. We agree that this section could benefit from a somewhat

rearrangement of the sentences. We have therefore made changes accordingly.

Authors’ action: The section now reads: ‘The prognostic factors involve both pre-trauma risk factors

[20, 21] and post-injury health factors. The post-injury health factors include the level of initial neck-

pain and cervical range of motion directly after the trauma. Most collision variables reported have

been shown to not be associated with the prognosis. Previous pain experiences, psychological

distress as well as socioeconomic situation and education have been reported to negatively influence

recovery to various degrees. Recent studies have reported links between pre- and post-injury self-

reported health care consultation and health status.’

Methods:

It was confusing that sick leave was captured only for two years post injury and the rest three years

post injury. In part, changing the location at which this information is presented in the methods section

may alleviate this. Sick leave timeframe is located in the ‘data sources’ subsection and the follow-up

of the subjects was reported in the ‘Neck injury cohort’ subsection of ‘Study cohorts’. It is suggested

that the sentence “sick leave data was available . . .” on page 7 be moved to page 8 at the end of the

Neck injury cohort subsection.

Authors’ action: We have moved this sentence as suggested.

Page 7 under neck injury cohort, the sentence starting with “We excluded all cases. . .” It may be

clearer to write out the range in years as ‘between 1998 and 2007- up until the month before

diagnosis’.

Authors’ reply: Thank you for this suggestion that facilitates the reading.

Authors’ action: The sentence have been changed accordingly, and now reads: ‘We excluded all

cases with any record of an injury involving the head and or neck (ICD-10-SE chapter S00-S19)

between 1998 and 2007- up until the month before diagnosis (Figure 1).’

Reference cohorts

- Is there a reason why reference 3 was not the only cohort included in the study? For example, were

there concerns with overmatching?

Authors’ reply: Our primary focus was to compare to the general population (not matched on socio-

economy etc.). However, we did include two sensitivity analyses to evaluate the effect on the

associations after matching on education and having at least one health care consultation, the

differences remained although slightly lower (as mentioned in the manuscript). For simplicity, we

decided to use reference group 1 as the primary reference groups as determined a priori.

It is suggested that Table 1 be moved to the results section as it includes a description of the cohorts

based on educational level.


Authors’ action: Table 1 has been moved to the result section.



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Outcomes:

Page 9. Why was two years before injury chosen as the timeframe to categorize patients as low,

frequent, or high-frequent users? It seems odd that total information was captured for all participants

three years before injury and all of the data was not used to categorize these patients. How might the

story change if all of this data was used.

Authors’ reply: thank you for pointing this out. This is an error in the manuscript, from pre-final version

where we only analyzed two years before injury. In the study the cut-offs were based on all three

years prior to the injury.

Authors’ action: The sentence have been corrected, and it now read: ‘Based on the median (quartile

1[Q1]; quartile 3 [Q3]) number of consultations in the reference group (References 1) the three year

period prior to….’

Statistical analysis – This section could use more clarity in terms of identifying in detail which

variables where analyzed with which statistical tools. Why not report Odds Ratios along with

attributable risk?

Authors’ reply: We appreciate this suggestion and concerns. However, we suggest that given the

cohort study design risk ratios are more appropriate to use.

Authors’ action: We have changed this section and extended the part about attributable risks to also

include the risk ratios (not odds ratios). The last part of the section now reads:

“Attributable risk for change between consultation level groups pre- to post-injury explained by the

injury diagnosis was computed. The attributable risk was calculated as the risk in the group of neck

injured patients group minus the risk in the reference group.

Additionally we computed risk ratios (RR) for patients with injury switching group after injury compared

to the references.’ A two-tailed p-value of 0.05 or less was considered to be statistically

significant.This was done for low, low and frequent, and frequent consulter’s pre injury, respectively. A

two-tailed p-value of 0.05 or less was considered to be statistically significant. All analyses were

performed using SAS software version 9.3 (SAS Institute Inc, Cary, North Carolina).”

Multiple T-tests across subgroups are not typically suggested without error correction, it is suggested

that the authors justify this practice. Also, please report that variance was equal across groups and a

t-test taking unequal sample size into account was used.

Authors’ reply: We thank you for this important comment, and agree that error correction often is

presented along with multiple comparisons. However we suggest correction for multiple testing (i.e

Bonferroni, Holm-Bonferroni or similar) is not absolutely indicated we have however changed our

significant level to be 99%. Given our major changes of statistical analysis this point is less of a

problem, we believe.

Authors’ action: We have made some clarification on the use of t-test test taking unequal sample size

into account and also regarding the use of 99% significant level, see page 11 statistical analysis.

Also it appears that there was comparison of count data between groups, subgroups, and years using

t-tests or non-parametric tests. This practice should be justified – statistical analysis of count data as

continuous is only acceptable if there are sufficient levels to each variable. Otherwise models could

be constructed to take confounders into account and it is suggested that the authors consider

analyzing the data using a Poisson distribution.

Authors’ reply: We agree with this comment as discussed in previous comments. We agree and think

this is a valid point and have changed the analysis accordingly.

Authors’ action: In the comparisons of count data, all analyses have been redone using considering a

non- normal distribution. We have introduced the Jonckheere-Terpstra test and also negative binomial

regression models. This is explained in the statistical section, page 10.

Results:

This section needs more organization. Please consider organizing according to

Cohort characteristics



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Group results

Stratified analyses

Diagnoses treated

Sick leave

Changes over time (referred to in the analysis but not specifically addressed in its own section)

Authors’ reply: We thank you for this suggestion on how we can approve the organization of our

manuscript.

Authors’ action: The result section has undergone a major change in its organization, based on your

suggestions. Particular the section on changes over time has been highlighted and risk ratios and

their 99% CIs have been added as have a table over risk ratios per year as suggested below.

Cohort characteristics:

For clarity it is suggested that the words, “in an acute, non-planned visit” be added after the word

‘physician’ in the first sentence in this section.

Authors’ reply: Thank you for this suggestion that clarifies the results.

Authors’ action: The words have been inserted and the sentence now reads: ‘Between January 1

2007 and December 31 2008, 1443 adult residents (54% women) were diagnosed with neck injury

(ICD-10 code S13.4) by a physician in an acute, non-planned visit and fulfilled our eligibility criterion

(no registered head/neck injury since 1998 up until the “screening” month) (figure 1, 2).’

Group results Consider reporting how the neck injured consulted as a group relative to the references

in the 3 years prior to the injury. It is not surprising that they consulted more over the 6 year period

when a major injury took place within this cohort.

Authors’ reply: We thank you for this suggestion, however there might have expressed this poorly, the

findings was that there was a difference between patients with neck injury and the references, every

year throughout the study period.

Authors’ action: we have changed the sentence in order to clarify this. The sentence now reads: ‘Over

the six-year study period, the neck injury cohort had significantly more health care consultations,

every year, than each of the three different reference groups (p<0.0001).’

Top of page 12 first full sentence, starting with “The mean age, . . .” you speak to the neck injured and

primary references here but in the next sentence you do not refer to any groups. Is the first sentence

differentiated because the secondary references were different? If not, it is suggested that the words,

“neck injured and primary references of” be removed from this sentence to improve clarity.

Authors’ reply: Thank you for pointing this unclear sentence out. We agree that this is somewhat hard

to follow.

Authors’ action: Starting after (figure 3) the last part of this paragraph has been changed. It now

reads: ‘When analysing differences between the patients with neck injury and the primary reference

group, the mean age was higher in the neck injured and primary references of high-frequent

consulters compared to their corresponding low-frequent consulters (41 vs. 35 years in cases,

p<0.0001). Women were overrepresented in the group of high-frequent consulters and

underrepresented in low-frequent consulters, both among patients diagnosed with neck injury and

their references (p<0.0001) (table 2).’

Stratified analyses: (If I am understanding correctly the discussion of your stratified analyses starts on

page 12, second paragraph)

Page 12, second paragraph starting “of the neck injured”. It is suggested that this falls under a

different heading as the outcome is not health care consultations per se, but the transition in

healthcare user classification. This appears to be an area in which an odds ratio would be suitable.

Authors’ reply: We agree with this suggestion that a risk ratio (RR) may be suitable here. We initially

chose to only present the attributable risk, but we have now decided to include the RRs as well.



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Authors’ action: The result section has undergone a major change in its organization, based on your

suggestions. The label Change over time has been inserted, under which RR (99% CI) have been

added as have a table over RR per year as suggested.

In the methods section outline for the reader that you intend to identify corresponding risk and

attributable risk and how this is done. On page 9 you refer to assessing the absolute portion of those

injured – please describe how this was done for your reader.

Authors’ action: A section on attributable risk assessment has been added to the statistics section.

This section reads: ‘Attributable risk for change between consultation level groups pre- to post-injury

explained by the injury diagnosis was computed. The risk was calculated as the risk in the group of

neck injured patients group - the risk in the reference group.

We also computed risk ratios (RR) (99% CI) for patients with injury switching group after injury

compared to the references.’

Page 12, paragraph starting, “In the stratified analyses, . . .” see comments on Changes over time

below.

Authors’ action: reorganization of manuscript has been done accordingly.

Please review your calculation of attributable risk. By plugging in the case-control numbers into an

immediate form program in Stata, I obtained an Odds Ratio of 2.47 and attributable risk percentage of

59% for transitioning from a low/medium frequency user to a high frequency user following neck

injury. In many respects this is expected in the first year of treatment. I would be interested in a table

that reports the odds of transitioning from low frequency to high frequency at each year of follow-up.

This nicely supports the introduction that there are a lot of people who are not improving following

acute neck injury.

Authors’ reply: Due to the cohort design of our study (this is actually not primarily a case-control

design as we study health care utilization and sick leave (=outcomes) in a cohort exposed to injury vs.

a reference cohort), we suggest to calculate risk ratios. Hence the, sample is selected based on an

exposure. We are well aware it is possible to argue the other way around, at least for the evaluations

of sick leave and consultation history before the trauma diagnosis.

Authors’ action: RR (99% CI) has been included in a table 5 in this section, along with attributable risk

(AR). RR and AR are presented by year after injury.

Page 14, second sentence beginning with “the proportion of subjects who were classified as low-

frequent among neck injured . . .” It appears prior to the injury there was a greater percentage of the

neck injured group who were in the low-frequent consulters category 26 v 14% - is this a mistake?

How does this fit into the overall message of the paper – that the neck injured consulted more on

average than the references? Also this sentence appears misplaced, it is suggested that this

sentence would be better placed in page 12 within the paragraph starting, “of the neck injured . . .”

Authors’ reply: Thank you for noticing this, yes it’s a mistake. The numbers are 27 vs. 35% in patients

vs. references (table 2).

Authors’ action: This sentence has been corrected and also moved to the section on stratified

analyses.

Diagnoses treated

The content on page 14 can be organized under this heading.

Sick leave, Page 16

The sentence starting, “Among the cases . . .”, The mean number of sick days was higher but was

this significantly different? Please clarify whether this difference was significant. The percentages

reported in table 4 seem close for the low and frequent users. A correlation between sick leave days

and health care consultations before injury is expected and not particularly newsworthy. In the final

sentence, is the increase in sick days over the two years under study? How did year two look relative



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to year 1? Perhaps this could be considered in the next section my suggested reorganization is taken.

Authors ‘reply: Thank you for this question, and we apologize for not including the statistics behind,

the differences was significant.

Authors’ Action: We have added information regarding the significant differences between groups.

And also specified that the difference between neck injured and references seen after injury regarding

sick days, are both valid for year 1, 2 and 3 after the injury. This specific sentence now reads: ‘The

number of mean sick leave days before neck injury were correlated to the number of health care

consultations before (ρ=0.47 (99% CI 0.39-0.48)), and year one (ρ=0.31 (99% CI0.25-0.35)) two

(ρ=0.30 (99% CI 0.24-0.34)) and three after neck injury (ρ=0.22 (0.17-0.27)).’

We have introduced “Diagnoses” as a new heading. We have also included results over change over

time regarding sick days.

Changes over time

There is no specific discussion to changes over time in its own section but it holds so much

importance to the message of this paper. It would be fitting to have a section specifically devoted to

comparing baseline to Year 1 versus Year 2 versus Year 3.

On page 12, the portion starting with, “In the stratified analyses . . . ”. This would be great to move to

this section and expand on it here.

Authors ‘reply: We really appreciate this comment and have reorganized our result after your

suggestions as described in previous comments.

Discussion:

Ultimately it is not surprising that individuals use more medical care following an acute neck injury (at

3-6 months) – in fact, this may be an appropriate use of services. The fact that some low users of

healthcare remain low users even after an acute injury may be problematic given the nature of the

injuries under study. Might this, in fact, increase the likelihood that chronic pain becomes established?

Do we know what they right use of healthcare services is? Perhaps this should be considered as a

limitation or a discussion point. These subgroups may be poor representations of identifying what

appropriate use might be.

However, it is interesting that individuals persist as high users of health care in subsequent years, up

to year 3. I believe this article is best suited to focus on this in relation to appropriate use.

Authors’ reply: We agree that this important to discuss and highlight.

If the conclusion states previous consultation history should be taken into account, how do the

authors propose to do this? Via questionnaire at intake? How would management change?

Authors’ reply: Thanks you for this important note. We have omitted this part of the conclusion, see

comment i) by reviewer 1 page 5.

In the end you are saying that there are individuals who tend to use our health system differently low,

frequent, and high users and this pattern changes slightly post injury. OK, how does this help me as a

clinician?

Authors’ reply: We appreciate this question; however, more research is needed to potentially

incorporate our finding into the clinical work.

Table 3 is very busy and difficult to read.

Authors’ reply: We can understand that this table seems hard to read and interpret, however we feel

that both the aspect of number of people being diagnosed and the mean numbers they get a

diagnosis is import and provide different aspect to the reader. Because of this we suggest to keep

table 3 as it is.

Table 4:



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I only compared the low-frequent groups on sick leave however, when comparing the proportions in

table 4, although odds were increased for sick leave due to neck injury the 95% CI for the odds ratio

crossed 0 and the chi square was not significant. By what methodology were significant differences

found between these groups? I am assuming you tested the difference in the proportions here. This is

where more specific detail is required in the methods section to allow a user to reproduce your

results.

Authors’ reply: We apologize for this confusion, and very much appreciate your careful review. This is

an error no significant were found here. As can be seen in the text under the figure by the terminology

used, this is the pre-final version. Again we apologize for this error.

Authors’action. The text under table 4 has been deleted.

Figure 4. In this figure it appears that there is also a transition from high to low utilization. This should

be discussed as to why this might occur.

Authors’ reply: It is likely that some people with neck injury have consulted due to other important

health issues this period, i.e., before the injury, of which in some persons these other problems have

naturally subdued or been cured. The figures are however small among the high frequent consulters

who were neck injured, n=40 (4.2%).

Figure 5. Are we to assume that -3 months is representative of mean healthcare consultations over

the previous 3 year period?

Authors’ reply: Figure 5 aims to describe the consultation pattern in more detail after injury based on

pre-injury consultation level. We wanted to give the reader a possibility to see the change in months

rather than in years in this figure. In order to facilitate this (simply to make the figure more readable),

we started at 3 month before injury. This level is in line with the level throughout all three previous

years.

Authors’ action: The time-period has been explained under the method’s section. A new sentence

reads, page 9 line 9: ‘We present the numbers per year throughout with one exception; to study the

number of consultations in detail after injury we display mean number of consultation within each

subgroup by quarters of a year starting three months pre-injury.’.

We have also pointed this out in the figure legend.

Limitations:

In addition to other suggested additions, please discuss the limitation associated with having to

eliminate diagnoses from private care as noted on page 6 – this will speak to the generalizability of

these findings in countries where most of the management occurs in a private system.

Authors’ reply: We agree this is important. Although some practices in Sweden are privately run, they

are still publicly financed. This means that everyone is free to seek health care wherever you chose,

and regardless of the practice is private or public; the cost for the patient is similar.

Authors’ action: We have added a section on the loss to private care under limitations page 25 line 6.

Quote “In Sweden everyone is entitled free health care. Some practices are however private run, still

public financed. This means that everyone is free to seek health care wherever you chose, and

regardless of the practice is run private or public in a vast majority of the cases the cost will for the

patient be similar. For hospitalized care only public options exist. In 2010 60% of all patients sought

only public care, 30% both public and private care and 10% sought only private care (not captured in

SHCR). Among those only seeking private care 60% were women and the ages 30-50 were

overrepresented.”

VERSION 2 – REVIEW

REVIEWER Daniel Pinto Assistant Professor, Physical Therapy and Human Movement Sciences/ Center for Healthcare Studies



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REVIEW RETURNED 23-Jul-2013

THE STUDY Only minor errors: Page 6 lines 20-21 - singular/plural misuse. "Only cases . . . is included" Should read "Only cases are included" Page 21, line 20. Sentence starting with consultations is missing several commas. Same page, line 21 could be reworded to improve clarity. For example. "This group will be a special challenge for health care providers" requiring that additional attention be paid to prevent the development of chronicity. Page 22 sentences starting on line 5 and concluding on line 8 lacks appropriate punctuation.



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peer review history article details title …page 1, line 6: the word ‘still’ is not necessary....

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