Responsiveness of health state utility values in knee osteoarthritis

Adaptive tests are increasingly being used to assess health-related quality of life in patients with a variety of medical conditions, including osteoarthritis (OA) of the knee. This approach has recently been used to assess health state utility valuations (HSUV) for use in quality-adjusted life-year calculations. To accurately assess incremental value for money, these tools must be responsive. Therefore, we examined the responsiveness of the Health Utilities Index mark 3 (HUI3) and Paper Adaptive Test-5D (PAT-5DQOL) in a group of patients with knee OA.

We used patient-level data from a randomized controlled trial evaluating a pharmacist-initiated multidisciplinary intervention in newly diagnosed patients with knee OA. The mean change for utility scores from baseline to 6 months was calculated, as well as effect size (ES) and standardized response mean (SRM) for the HUI3 and PAT-5DQOL, and generalized additive model plots, using the Western Ontario and McMaster Osteoarthritis index as a reference standard.

When patients were assessed based on whether their condition had improved, remained unchanged, or worsened over time, the PAT-5DQOL showed greater responsiveness in patients whose condition had either improved or worsened. ES and SRM were generally small for both instruments.

The PAT-5DQOL is more responsive to change over time than the HUI3 in patients with knee OA.