Development of a model for case-mix adjustment of pressure ulcer prevalence rates

BACKGROUND. Acute care hospitals participating in the Dutch national pressure ulcer prevalence survey use the results of this survey to compare their outcomes and assess their quality of care regarding pressure ulcer prevention. The development of a model for case-mix adjustment is essential for the use of these prevalence rates as an outcome measure. OBJECTIVE. The development of a valid model for case-mix adjustment to compare the prevalence rates in the acute care hospitals that participated in the 1998 Dutch pressure ulcer prevalence survey, for the purpose of performance comparisons among the hospitals. DESIGN. Cross-sectional design. SUBJECTS. Subjects were patients residing in the 43 acute care hospitals that participated in the national pressure ulcer prevalence survey on May 26, 1998. MEASURES. The study examined the validity of a model for case-mix adjustment of pressure ulcer prevalence rates and compared hospitals to evaluate the impact of adjusted prevalence rates on their performance. RESULTS. A logistic model was developed for case-mix adjustment, using age, malnutrition, incontinence, activity, mobility, sensory perception, friction and shear, and ward specialty. This model was found to have content, construct, and internal validity. Case-mix adjustment influenced the hospitals' performance. CONCLUSION. The data of the national pressure ulcer prevalence survey can be used to develop a valid model for case-mix adjustment. Conclusions about the quality of care were influenced by the use of case-mix adjusted outcomes as a measure of this quality.