Do severity measures explain differences in length of hospital stay? The case of hip fracture

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Department of Quantitative Health Sciences

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Aged; Aged, 80 and over; Databases, Factual; Diagnosis-Related Groups; Female; Health Services Research; Hip Fractures; Hospitals; Humans; Length of Stay; Male; Models, Statistical; Outliers, DRG; Prognosis; Regression Analysis; *Severity of Illness Index; United States; Utilization Review


Biostatistics | Epidemiology | Health Services Research


DATA SOURCES/STUDY SETTING: Data on admissions to 80 hospitals nationwide in the 1992 MedisGroups Comparative Database.

STUDY DESIGN: For each of 14 severity measures, LOS was regressed on patient age/sex, DRG, and severity score. Regressions were performed on trimmed and untrimmed data. R-squared was used to evaluate model performance. For each severity measure for each hospital, we calculated the expected LOS and the z-score, a measure of the deviation of observed from expected LOS. We ranked hospitals by z-scores.

DATA EXTRACTION: All patients admitted for initial surgical repair of a hip fracture, defined by DRG, diagnosis, and procedure codes.

PRINCIPAL FINDINGS: The 5,664 patients had a mean (s.d.) LOS of 11.9 (8.9) days. Cross-validated R-squared values from the multivariable regressions (trimmed data) ranged from 0.041 (Comorbidity Index) to 0.165 (APR-DRGs). Using untrimmed data, observed average LOS for hospitals ranged from 7.6 to 23.9 days. The 14 severity measures showed excellent agreement in ranking hospitals based on z-scores. No severity measure explained the differences between hospitals with the shortest and longest LOS.

CONCLUSIONS: Hospitals differed widely in their mean LOS for hip fracture patients, and severity adjustment did little to explain these differences.


Health Serv Res. 1996 Oct;31(4):365-85. Link to article on publisher's site

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Health services research

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Link to Article in PubMed