Measurement properties for the revised patient-reported OsteoArthritis Quality Indicator questionnaire

To assess validity, reliability, responsiveness and interpretability of the revised OsteoArthritis Quality Indicator (OA-QI) questionnaire version 2 (v2) assessing patient-reported quality of osteoarthritis care.

The OA-QI v2 (16 items, score range 0-100 (100 = best score)) was included in a longitudinal cohort study. Attendees of a 4.5 h osteoarthritis patient education programme at Diakonhjemmet Hospital, Norway, completed the OA-QI at four time points: 2 weeks before, immediately before, immediately after, and 3 months after the programme. Test-retest reliability and measurement error over a 2-week time period were assessed in those that had not seen health professionals in the interim. Construct validity and responsiveness were assessed with predefined hypotheses. Floor and ceiling effects, smallest detectable change (SDC_95%) and minimal important change (MIC) were assessed to evaluate interpretability.

The intraclass correlation coefficient for all 16 items was 0.89. For single items the test-retest kappa estimates ranged 0.38-0.85 and percent agreement 69-92%. Construct validity was acceptable with all six predefined hypotheses confirmed. Responsiveness was acceptable with 33 of 48 and three of four predefined hypotheses confirmed for single items and all items, respectively. There were no floor or ceiling effects. The SDC_95% was 29.1 and 3.0 at the individual and group levels, respectively. MIC was 20.4.

The OA-QI v2 had higher reliability estimates compared to v1, showed acceptable validity, and is the recommended version for future use. The results of responsiveness testing further support the use of the OA-QI v2 as an outcome measure in studies aiming to improve osteoarthritis care.