Time in the Hospital is Not Always Normal: What does one year’s worth of studies tell us?

Michael Distefano MD, A.Chantal Caviness, MD, MPH PhD, Binita Patel MD, Angelo P Giardino, MD, PhD, MPH



Context: Patient length of hospital stay (LOS) is an important measure of timeliness and efficiency in healthcare quality studies.

Objective: Because conclusions drawn about LOS may be influenced by assumptions of variable distribution, we sought to determine the quality of LOS data analysis in published pediatric clinical studies. 

Study Selection: Articles from PubMed were included if they were of pediatric clinical studies published in English for a one year period of time between 6/1/2009 and 5/31/2010 where LOS was an outcome variable.

Data Extraction: The reported statistical approach was extracted from published manuscripts by 2 independent reviewers and included hospital LOS: distribution, measures of central tendency, and methods of statistical comparisons. 

Results: Of 795 identified studies, 214 were included: only 33 reported LOS distribution of which 5 used the incorrect measure of central tendency.  One hundred and two studies reported LOS means, 64 reported medians, and 22 reported both means and medians.  Of 142 comparative studies, 61 used non-parametric methods, 53 parametric methods, 1 used both parametric and non-parametric methods, 7 transformed the variable, 18 did not specify, and 2 were missing.

Conclusions: Although used frequently as a measure of healthcare outcomes, there is wide variation in the statistical approach and reporting of LOS.  We recommend that, at a minimum, investigators should follow the International Committee of Medical Journal Editors Uniform Requirements for Manuscripts Submitted to Biomedical Journals reporting of statistical data.  Furthermore, investigators should evaluate, report, and use LOS distributions to inform LOS analyses. 



Length of stay, quality, efficiency

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Anderson, T.W., Darling D.A. (1952). Asymptotic theory of certain "goodness-of-fit" criteria based on stochastic processes. Annals of Mathematical Statistics. 23,193-212.

Bailar, J.C., III, Mosteller, F. (1988). Guidelines for statistical reporting in articles for medical journals. Amplifications and explanations. Annals of Internal Medicine. Feb;108(2), 266-273.

Boudreaux, E.D., D'Autremont, S., Wood, K., Jones, G.N. (2004).Predictors of emergency department patient satisfaction: stability over 17 months. Academic Emergency Medicine, Jan 2, 11(1), 51-58.

Bursch., B. Beezy, J., Shaw, R. (1993). Emergency department satisfaction: what matters most? Annals of Emergency Medicine, Mar;22(3),586-591.

Clarke, A. (2002). Length of in-hospital stay and its relationship to quality of care. Quality and Safety in Health Care, Sep,11(3),209-210.

Clarke, A., Rosen, R. (2001. Length of stay. How short should hospital care be? Eurpoean Journal of Public Health, Jun,11(2), 166-170.

D'Agostino, R.B., Belanger, A.J. (1990). A suggestion for using powerful and informative tests of normality. The American Statistician. 1990;44(4):316-321.

International Committee of Medical Journal Editors. (1998). Uniform requirements for manuscripts submitted to biomedical journals. Annals of Internal Medicine, Feb, 108(2),258-265.

Institute of Medicine. (2001).(U.S.). Committee on Quality of Health Care in America. Crossing the quality chasm : a new health system for the 21st century. Washington, D.C.: National Academy Press.

Landrigan, C.P. (2005). The safety of inpatient pediatrics: preventing medical errors and injuries among hospitalized children. Pediatric Clinics of North America,. Aug, 52(4), 979-993, vii.

Lilliefors, H. (1967). On the Kolmogorov-Smirnov test for normality with mean and variance unknown. Journal of the American Statitical Association. 62:, 399-402.

Shapiro. S., Wilk, M. (1965).An analysis of variance test for normality (complete samples). Biometrika, 52(3-4):, 591-611.

Stockwell, J.A. (2007). Nosocomial infections in the pediatric intensive care unit: affecting the impact on safety and outcome. Pediatric Critical Care Medicine, Mar, 8(2 Suppl), S21-37.

Thomas, J.W., Guire, K.E., Horvat, G.G. (1997). Is patient length of stay related to quality of care? Hospital & Health Services Administration, Winter 42(4),489-507.

Thompson, D.A., Yarnold, P.R., Williams, D.R., Adams, S.L. (1996). Effects of actual waiting time, perceived waiting time, information delivery, and expressive quality on patient satisfaction in the emergency department. Annals of Emergency Medicine., Dec, 28(6),657-665.

United States Deptartment of Health and Human Services, United States. (2007) Agency for Healthcare Research and Quality. 2007 national healthcare quality report. Rockville, Md.

DOI: http://dx.doi.org/10.18103/mra.v0i3.295


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