RATING LONG-TERM-CARE FACILITIES ON PRESSURE ULCER DEVELOPMENT - IMPORTANCE OF CASE-MIX ADJUSTMENT

Objective: To determine the importance of case-mix adjustment in inter preting differences in rates of pressure ulcer development in Departme nt of Veterans Affairs long-term care facilities. Design: A sample ass embled from the Patient Assessment File, a Veterans Affairs administra tive database, was used to derive predictors of pressure ulcer develop ment; the resulting model was validated in a separate sample. Facility -level rates of pressure ulcer development, both unadjusted long-term care and adjusted for case mix using the predictive model, were compar ed. Setting: Department of Veterans Affairs long-term care facilities. Patients: The derivation sample consisted of 31 150 intermediate medi cine and nursing home residents who were initially free of pressure ul cers and were institutionalized between October 1991 and April 1993. T he validation sample consisted of 17 946 residents institutionalized f rom April 1993 to October 1993. Measurement: Development of a stage 2 or greater pressure ulcer. Results: 11 factors predicted pressure ulce r development. Validated performance properties of the resulting model were good. Model-predicted rates of pressure ulcer development at ind ividual long-term care facilities varied from 1.9% to 6.3%, and observ ed rates ranged from 0% to 10.9%. Case-mix-adjusted rates and ranks of facilities differed considerably from unadjusted ratings. For example , among five facilities that were identified as high outliers on the b asis of unadjusted rates, two remained as outliers after adjustment fo r case mix. Conclusions: Gong-term care facilities differ in case mix. Adjustments for case mix result in different judgments about facility performance and should be used when facility incidence rates are comp ared.