(1) To assess responsiveness of the EQ-5D-5L compared to Oxford hip and knee scores and the SF-12 in osteoarthritis patients undergoing total hip (THR) or knee (TKR) replacement surgery; (2) to compare distribution and anchor-based methods of assessing responsiveness.
Questionnaires were mailed to consecutive patients following surgeon referral for primary THR or TKR and 1 year post-surgery. We assessed effect size (ES), standardized response mean (SRM), and standard error of measurement (SEM). Minimum important difference (MID) was the mean change in patients reporting somewhat better in hip or knee, health in general, and those who were satisfied with surgery (5-point scales). Responders were compared using MID versus 1 and 2SEM.
The sample of 537 (50% TKR) was composed of 56% female with a mean age of 64 years (SD 10). EQ-5D-5L ES was 1.86 (THR) and 1.19 (TKR) compared to 3.00 and 2.05 for Oxford scores, respectively. MID for the EQ-5D-5L was 0.22 (THR) and 0.20 (TKR) for patients who rated their hip or knee as somewhat better. There was a wide variation in the MID and the percentage of responders, depending on the joint, method of assessment, and the outcome measure. The percent agreement of responder classification using 2SEM vs. MID ranged from 79.6 to 99.6% for the EQ-5D-5L and from 69.4 to 94.8% for the Oxford scores.
Responsiveness of the EQ-5D-5L was acceptable in TKR and THR. Caution should be taken in interpreting responder to TJR based on only one method of assessment.