Prediction of peak flow values followed by feedback improves perception of lung function and adherence to inhaled corticosteroids in children with asthma

SCH Journal Club

26th March 2013

AimTo determine whether predicting peak flow

value and comparing with actual peak flow

value in asthmatic children will improve

perception of their lung function

Objectives• Search literature for relevant paper

• Critically appraise the paper using CASP framework

• Determine validity of paper

• Assess whether able to apply to clinical practice

Clinical Scenario• 10 year old boy known to have poor control of

his asthma attends the respiratory clinic for routine review.

• He is noted to have had several admissions to hospital since his last review despite maximal treatment, always attending with either acute severe or life-threatening symptoms.

Background• Many factors can contribute to the poor control of

asthma • One such factor which has been shown to contribute is

the discrepancy between objective measures of airway obstruction and symptom perception.

• This can result in a delay in seeking treatment for acute exacerbations due to an under-perception of the degree of bronchoconstriction

Question Arising• Does our patient’s perception of his symptoms correlate

with the level of his lung function and is he able to recognise when his lung function has become compromised?

• If not is there a proven way to improve his perception of lung function thereby improving the control of his asthma and reducing his acute admissions to hospital?

Clinical Question

Population In children with poorly-controlled asthma

Intervention is there a simple intervention to

Comparison

Outcome improve perception of lung function and thereby improve control of symptoms?

Literature Search

[asthma]

AND [perception OR awareness]

AND [(lung AND function) OR (airway AND obstruction)]

AND [(hospital OR (secondary AND care) OR (emergency AND healthcare)].

Limited to [child 0 – 18 years AND English language]

Prediction of peak flow values followed by feedback improves perception of lung function and adherence to inhaled corticosteroids in children with asthma

Jonathan M Feldman, Haley Kutner, Lynne matte, Michelle Lupkin, Dara Steinberg, Kimberly Sidora-Arcoleo, Denise Serebrisky, Karen Warman

Thorax 2012;67:1040 - 1045

Method• Patients recruited from asthma clinics, primary

care clinics, ED and mailings• Restricted to Puerto Rican, African-American

and Afro-Caribbean ethnic groups• Confirmed diagnosis of asthma with breathing

difficulties in past year

• Exclusion criteria included cognitive learning disability, vocal cord dysfunction, inability to conduct spirometry

1st Study GroupFEEDBACK GROUP

2nd Study GroupNON-FEEDBACK GROUP

• Initial training on use of spirometer to ensure correct technique •Over a six week period recruits assessed their lung function twice a day at set times

•Each recruit predicted their PEF and recorded this on their spirometer

• They then performed three consecutive PEF and documented the “best of 3” PEF

• Results of PEF value were fed-back to recruits to be able to compare with their predictions

• However they were unable to alter predicted PEF

• Initial training on use of spirometer to ensure correct technique •Over a six week period recruits assessed their lung function twice a day at set times

• Each recruit predicted their PEF and recorded this on their spirometer

• They then performed three consecutive PEF and documented the “best of 3” PEF

• Blinded to value of PEF

Figure 1 Asthma risk grid (adaptedwith permission from OceanSidePublications, Inc from Klein et al18).Accurate zone: boxes 1, 5, 9 and±10% wedge; magnification zone:boxes 2, 3 and 6; danger zone: boxes4, 7 and 8. PEF, peak expiratory flow.

Outcome Measures

1. Asthma Risk Grid (Figure 1) was used to determine the % of predictions from each recruit in (i) accurate, (ii) under-perception and (iii) over-perception zones as a measure of the perception of respiratory compromise

2. Adherence to ICS inhalers during study period was monitored using doser-devices (95/192; -10)

3. Use of quick-relief metered dose inhaler was monitored during study period using doser-devices (181/192; -16)

Figure 2 Participant enrolment in thepeak expiratory flow (PEF) feedbackand no feedback conditions

A/ Are the results of the study valid? – Screening Questions

1. Did the study address a clearly focused question?

Yes Can’t Tell No ■ □ □

HINT: A question can be focused in terms of?

• the population studied• the risk factors studied• the outcomes considered• is it clear whether the study tried to detect a beneficial or harmful effect?

“We hypothesised that children who receive feedback on PEF predictions would have less under-perception of respiratory compromise, better ICS adherence and less quick relief medication use than children who do not receive feedback”

Page 1041 end of first paragraph

A/ Are the results of the study valid? - Screening Questions

2. Did the author use an appropriate method to answer their question?

Yes Can’t Tell No ■ □ □

• is a cohort study a good way of answering the question under the circumstances?

•Did it address the study question?

• why not use a randomised control trial? - but two groups similar in baseline characteristics (table 1) - difficult to blind to intervention

• Yes – the study determined perception of lung function in each group, comparing the accuracy of predictions with actual readings of lung function and then compared the feedback group with the non-feedback group; also looked at inhaler use

A/ Are the results of the study valid - Detailed Questions3. Was the cohort recruited in an acceptable way?

Yes Can’t Tell No □ ■ □

• was the cohort representative of a defined population

• was there something special about the cohort?

• was everybody included who should have been included?

• Yes – defined ethnic population with confirmed diagnosis of asthma • No – baseline characteristics similar across feedback and non-feedback group (Table 1)

• Not sure – used convenience sampling (this is noted as a limitation of the study in the discussion)

• Limited inclusion criteria specified – e.g. age groups not mentioned

•No information on any individuals who declined to participate

4 Was the exposure accurately measured to minimize bias?

Yes Can’t Tell No ■ □ □

• Did they use subjective or objective measurements?

• Do the measures truly reflect what you want them to (have they been validated)?

• Were all the subjects classified into exposure groups using the same procedure?

The exposure was the process of predicting and recording actual PEF measurements with feedback on results for the feedback group and blinding of results with non-feedback group.

subjective measurement was the recruits’ prediction of lung function objective measurement was the recorded PEF * Potential for bias in blinded group through less motivation resulting in less effort with PEF performance but PEF results comparable between two groups

• This method for perception of pulmonary function has been used in previous studies

• Yes – procedure the same for each recruit over the study periods

5. Was the outcome accurately measured to minimize bias?

Yes Can’t Tell No ■ □ □

HINT: We are looking for measurement or classification bias: • Did they use subjective or objective measurements? • Do the measures truly reflect what you want them to (have they been validated)? • Has a reliable system been established for detecting all the cases (for measuring disease occurrence)? • Were the measurement methods similar in the different groups? • Were the subjects and/or the outcome assessor blinded to exposure (does this matter)?

The outcome is the percentage of PEF measurements falling into each category on the Asthma Risk Grid to determine whether those with feedback are more accurate at predicting lung function and the use of ICS and quick relief inhalers.

The measurements were the same in the two study groups

There was no blinding to exposure – impossible to do with subjects as this was the exposure being measured.

6 A Have the authors identified all important confounding factors?

Yes Can’t Tell No □ □ ■

List the ones you think might be important, that the author missed.

See Table 2, page 1043

DID NOT consider: Duration of diagnosis of asthma Asthma within primary care-giver? Environmental factors

B. Have they taken account of the confounding factors in the design and/or analysis?

Yes Can’t Tell No ■ □ □

HINT: • Look for restriction in design, and techniques eg modelling, stratified-, regression-, or sensitivity analysis to correct, control or adjust for confounding

Used analysis of covariance for analysis of data and included age and ethnicity as covariatesRepeated analysis excluding higher age group from feedback group and got similar results

7. A. Was the follow up of subjects complete enough?

Yes Can’t Tell No□ ■ □

7. B. Was the follow up of subjects long enough?

Yes Can’t Tell No □ ■ □

HINT:

• The good or bad effects should have had long enough to reveal themselves • The persons that are lost to follow-up may have different outcomes than those available for assessment • In an open or dynamic cohort, was there anything special about the outcome of the people leaving, or the exposure of the people entering the cohort?

• Effect with predicting PEF seen after initial training and maintained for study period of six weeks• BUT was effect continued? – ICS take 6 weeks to take effect so may have been beneficial to have longer study period to see real improvement in control of asthma (and therefore reduction in use of reliever medication)• Those lost to follow-up had similar demographic details

B/ What are the results?8 What are the results of this study?

Refer to Table 3 on page 1043

• What are the bottom line results?

• Have they reported the rate or the proportion between the exposed/unexposed, the ratio/the rate difference?

• How strong is the association between exposure and outcome (RR,)?

• What is the absolute risk reduction (ARR)?

• 60.7% +/- 2.3 of predictions in the PEF feedback group fell within the accurate zone compared to 48.2% +/- 2.5 of predictions in no-feedback group (p <0.001)

• 15.3% +/- 2.1 of predictions in the PEF feedback group fell within the danger zone compared to 41.6% +/- 2.3 of predictions in the no-feedback group (p <0.001)

• Increased adherence to ICS for duration of trial in feedback group (48.8% vs 27.5%)

• Increased use of quick-reliever inhalers for duration of trial in feedback group (41.9 puffs vs 21.8 puffs)

9. How precise are the results?

• Size of the confidence intervals ? One standard error of the mean used (= 68% sample mean within 1 standard error; i.e. 68% of the means will fall within percentages given) therefore results not that precise

10. Do you believe the results? Yes Can’t Tell No □ ■ □

• Big effect is hard to ignore! • Can it be due to bias, chance or confounding? • Are the design and methods of this study sufficiently flawed to make the results unreliable? • Consider Bradford Hills criteria (e.g. time sequence, dose-response gradient, biological plausibility, consistency).

• Don’t fully understand the statistics

• There does appear to be an improvement in the perception of lung function within the feedback group which I think is due to the use of feedback

• Use of inhalers less clear as smaller numbers

C/ Will the results help me locally?11. Can the results be applied to the local population?

Yes Can’t Tell No □ ■ □

HINT: Consider whether

• The subjects covered in the study could be sufficiently different from your population to cause concern

• Your local setting is likely to differ much from that of the study

• Can you quantify the local benefits and harms?

very different ethnic group compared to local population but it is possible that the results would be similar in different ethnic groups (previous studies have had similar results in a different ethnic group)

12. Do the results of this study fit with other available evidence?

Yes Can’t Tell No ■ □ □

Previous studies have used a similar protocol with Latino children and found similar results (end of first paragraph in Discussion, page 1044)

Previous studies have also shown the lack of incremental learning effect across time(second paragraph in Discussion, page 1044)

Summary and Conclusions• The study supports the suggestion that

predicting peak flow values followed by feedback does improve the perception of lung function in children with asthma from a specified ethnic group in USA.

• However there are flaws in the methodology and results are not clear compromising validity of paper and results

• Not sure that it could be applied to local population - ideally need to look at local population to determine similar effect.

Bottom Line• An interesting concept which has potential to improve

perception of lung function but needs further research to determine whether applicable to local population and whether there are benefits on the control of symptoms.