DO SEVERITY MEASURES EXPLAIN DIFFERENCES IN LENGTH OF HOSPITAL STAY -THE CASE OF HIP FRACTURE

Objective. To examine whether judgments about hospital length of stay (LOS) vary depending on the measure used to adjust for severity differ ences. 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/se x, 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 LO S and the z-score, a measure of the deviation of observed from expecte d 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 patien ts 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, o bserved average LOS for hospitals ranged from 7.6 to 23.9 days. The 14 severity measures showed excellent agreement in ranking hospitals bas ed on z-scores. No severity measure explained the differences between hospitals with the shortest and longest LOS. Conclusions. Hospitals di ffered widely in their mean LOS for hip fracture patients, and severit y adjustment did little to explain these differences.