Different Approaches for Case-Mix Adjustment of Patient-Reported Outcomes to Compare Healthcare Providers-Methodological Results of a Systematic Review.

Patient-reported outcomes (PROs) are increasingly being used to compare the quality of outcomes between different healthcare providers (medical practices, hospitals, rehabilitation facilities). However, such comparisons can only be fair if differences in the case-mix between different types of provider are taken into account. This can be achieved with adequate statistical case-mix adjustment (CMA). To date, there is a lack of overview studies on current CMA methods for PROs. The aim of this study was to investigate which approaches are currently used to report and examine PROs for case-mix-adjusted comparison between providers. A systematic MEDLINE literature search was conducted (February 2021). The results were examined by two reviewers. Articles were included if they compared (a) different healthcare providers using (b) case-mix-adjusted (c) patient-reported outcomes (all AND conditions). From 640 hits obtained, 11 articles were included in the analysis. A wide variety of patient characteristics were used as adjustors, and baseline PRO scores and basic sociodemographic and clinical information were included in all models. Overall, the adjustment models used vary considerably. This evaluation is an initial attempt to systematically investigate different CMA approaches for PROs. As a standardized approach has not yet been established, we suggest creating a consensus-based methodological guideline for case-mix adjustment of PROs.