International Journal of Cardiology 180 (2015) 151–153

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International Journal of Cardiology

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Letter to the Editor

Lack of "Weekend Effect" on Mortality for Pulmonary EmbolismAdmissions in 2011: Data from Nationwide Inpatient Sample

Smith Giri a, Ranjan Pathak b,⁎, Madan Raj Aryal b, Paras Karmacharya b, Vijaya Raj Bhatt c, Mike G. Martin d

a Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, USAb Department of Medicine, Reading Health System, West Reading, PA, USAc Department of Hematology and Oncology, University of Nebraska Medical Center, Omaha, NE, USAd The West Cancer Center, University of Tennessee Health Science Center, Memphis, TN, USA

⁎ Corresponding author at: ReadingHealth System, 6thReading, PA 19611, USA.

E-mail address: ranjanrp@gmail.com (R. Pathak).

http://dx.doi.org/10.1016/j.ijcard.2014.11.2010167-5273/© 2014 Elsevier Ireland Ltd. All rights reserved

a r t i c l e i n f o

Article history:

Received 23 November 2014Accepted 25 November 2014Available online 26 November 2014

Keywords:Pulmonary embolismWeekendWeekdayMortalityHCUPNIS

tients with PE, we included patients with secondary diagnosis code forPE and one of the following primary codes: respiratory failure(518.81), cardiogenic shock (785.51), cardiac arrest (427.5), secondarypulmonary hypertension (416.8), syncope (780.2), thrombolysis(99.10), and intubation or mechanical ventilation (96.04, 96.05, 96.70to 96.72).We excluded patients transferred from other healthcare facil-ities and all other patients with secondary diagnosis of PE. Our studyprotocol was exempted from review by the Institutional Review Boardof University of Nebraska Medical Center, Nebraska.

Baseline demographic characteristics (age, sex, and race), weekdayversus weekend admission, primary payer status, hospital region,Charlson co-morbidity index and data on hospital characteristics such

Acute pulmonary embolism (PE) continues to remain an importantpublic health problem with an estimated incidence of 112.3 cases per100,000 people in the United States [1]. Previous studies have shownsignificantly higher in-hospital mortality and length of stay (LOS) forweekend PE admissions [2,3]. Reduced staffing including physician cov-erage, reduced availability of diagnostic tests, and decreased use of inva-sive medical therapies during weekend may explain the increase inweekendmortality [3]. Although the cost of care of PE has increased sig-nificantly, recent improvements in the management of acute PE has re-sulted in a decline in the mortality and the LOS [4]. It remains unclear ifthis improvement has affected theweekend–weekday gap in outcomes.

We identified all PE admissions admitted to US hospitals from Janu-ary 1, 2011 to December 31, 2011 from the Nationwide Inpatient Sam-ple (NIS), Healthcare Cost and Utilization Project, and Agency forHealthcare Research and Quality [5]. NIS is the largest publicly availableall-payer inpatient care database in the US containing discharge-leveldata from 5 to 8 million hospital admissions from about 1000 hospitals,approximating a 20% sample of all community hospitals. We used theInternational Classification of Diseases, ninth edition, Clinical Modifica-tion (ICD-9-CM) codes (415.11, 415.13, 415.19, and 673.20 to 673.24) toidentify all patients ≥18 years of age with the diagnosis of PE admitted

Avenue and Spruce Street,West

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to the hospital in 2011. To ensure the inclusion of the critically ill pa-

as hospital region, location/teaching status and bed-size were extractedfrom the NIS database. Our outcome measures included all-cause in-hospital mortality, defined as “died” during the index hospitalizationin the NIS and LOS. Baseline patient and hospital characteristics werecompared using Pearson's Chi-square test for categorical variables andStudent's t-test for continuous variables. Standard logistic regressionwas used to examine the association between weekend admission andin-hospital mortality. We used sex, race, primary payer status, hospitalregion, teaching status/location, bed-size and thrombolysis in the finalregression model for in-hospital mortality. Statistical analysis was per-formed using Stata 13.1 (Stata Corp, College Station, TX) whichaccounted for the complex survey design and clustering. We used a 2-sided P-value of b0.05 to identify statistical significance.

A total of 41,210 PE admissions were identified out of which week-end admissions comprised of 22.4% (n = 9211) of all PE admissions.PE patients admitted on the weekend were found to have a medianage of 64,whichwas similar toweekday admissions (Table 1). No signif-icant differences were seen in the patient characteristics in terms of sex,race, hospital size, teaching status and geographic location of the hospi-tals between the weekend and weekday admission groups. Weekendadmission group had higher proportion of patients with Medicare andMedicaid insurance compared to private insurance (P b 0.001).

The overall in-hospitalmortality of PE patientswasdetermined to be5.2%. The unadjusted in-hospital mortality was significantly higheramong weekend versus weekday admissions (5.7% vs. 5.1%, OR 1.11,95% CI 1.01–1.22, P b 0.001). However, after adjustment for differencesin age, sex, race, insurance status, co-morbidities, administration ofthrombolytic therapy, hospital region and teaching status/location, the

Table 1Baseline Patient Characteristics for Admission on Weekdays Versus Weekends.

Characteristics All (n = 41,210) Weekdays (n = 31,999) Weekends (n = 9211) P

Age in years Median 64 (50–76) 64 (50–76) 64 (50–77) 0.99Mean ± SD 62.26 ± 17.50 62.26 ± 17.36 62.26 ± 17.82

Male sex 46.3 46.2 46.7 0.43Race White 73.9 74.2 73 0.18

Black 17.3 17.1 18Hispanic 5.4 5.3 5.6Others/unknown 3.4 3.4 3.4

Insurance status Medicare 50.6 50.4 51.4 b0.001Medicaid 9 8.8 9.8Private insurance 31.9 32.4 30Self-Pay 4.7 4.7 4.7No charge 0.5 0.5 0.6Other 3.3 3.2 3.6

Region Northeast 17.9 17.9 18 0.41Midwest 25.4 25.4 25.6South 37.4 37.6 36.8West 19.2 19.1 19.6

Location/teaching status Rural 13.4 13.4 13.5 0.83Urban nonteaching 43.2 43.3 43Urban teaching 43.4 43.3 43.6

Bed-size Small 13.2 13.3 12.7 0.2Medium 25 25 25Large 61.9 61.7 62.3

Charlson index 0 37.6 37.7 37.1 0.161 23.8 23.6 24.72 38.6 38.7 38.2

SD = standard deviation.

152 S. Giri et al. / International Journal of Cardiology 180 (2015) 151–153

in-hospital mortality was not significantly different (OR 1.07, 95% CI0.97–1.19, P = 0.18) (Table 2). The mean LOS was similar among pa-tients admitted on weekends and weekdays (5.57 ± 5.43 days, P =0.09).

Table 2Adjusted odds ratios for in-hospital mortality for patients admitted on weekends com-pared with weekdays.

Characteristic Adjusted OR forin-hospitalmortality

95% CI P

Weekendadmission

1.07 0.97–1.19 0.18

Female sex 1.06 0.96–1.17 0.24Race White 1 …

Black 1.19 1.05–1.36 0.01Hispanic 1.05 0.86–1.29 0.61Others/unknown 1.57 1.23–2.01 0.00

Insurance status Medicare 1 …

Medicaid 0.84 0.72–0.98 0.03Private insurance 0.69 0.61–0.78 0.00Self-pay 0.89 0.69–1.15 0.37No charge 0.92 0.4–2.13 0.85Other 0.75 0.55–1.03 0.07

Thrombolysis 1.31 0.77–2.2 0.32Region Northeast 1 …

Midwest 0.85 0.7–1.03 0.10South 1.03 0.87–1.21 0.74West 0.9 0.75–1.09 0.29

Location/teachingstatus

Rural 1 …

Urbannonteaching

1.29 1.08–1.55 0.01

Urban teaching 1.62 1.35–1.95 b0.001Bed-size Small 0.93 0.77–1.14 0.49

Medium 1 …

Large 1.08 0.94–1.24 0.30Charlson index 0 1 …

1 1.91 1.63–2.23 b0.0012 4.36 3.78–5.03 b0.001

OR = odds ratio.

The main findings of our study include the lack of weekend versusweekday differences in mortality rate among patients with PE. This isin contrast to previous studies that showed a higher mortality in PE pa-tients admitted during theweekends [2,3]. Recently, hospitals have uti-lized various practical analytical tools for efficient resourcemobilizationto overcome the weekend effect [6,7]. With careful allocation of humanresources, diagnostic services and procedures over the weekends, hos-pitals have successfully improved patient outcomes with a reasonablecost–benefit ratio. For instance, comprehensive stroke centers, withthe availability of stroke teams, therapeutic and diagnostic modalitiesaswell as ancillary staff during after-hours andweekends, have success-fully overcome the previously described “weekend effect” for stroke pa-tients [8].

We believe that our findings reflect recent improvement in theman-agement of patients with PE in the US. A previous study demonstratedreduction inmortality aswell as LOS of patients, attributed to increasingphysician awareness, as well as readily available diagnostic services [4].Spiral CT is currently the first-line diagnostic modality for PE and iswidely available [1]. In a survey of US physicians, round-the-clock avail-ability of CT scan was reported by about 90% of the respondents [9].With rising popularity of tele-radiology, virtual radiology and night-hawk system, hospitals have been able to expand radiology service cov-erage during the weekends [10].

The main strength of our study is a large sample size availablethrough a national database. However, like any administrative database,it is prone to coding errors. Coding practices differ between differenthospitals and regions. However, such practices are unlikely to differ be-tween weekend and weekdays of the same hospital. In NIS, weekendperiod is defined as the time period between Friday midnight and Sun-day midnight, which is not entirely representative of the “real world”weekend period.

Conflict of interest

The authors report no relationships that could be construed as a con-flict of interest.

153S. Giri et al. / International Journal of Cardiology 180 (2015) 151–153

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