Hip and Knee Disability and Osteoarthritis Outcome Scores Minimal Clinically Important Differences Vary by Payer Type: Implications for Mandatory Patient-Reported Outcome Reporting.

BACKGROUND: Recent mandates from the Centers for Medicare and Medicaid Services have tied patient-reported outcome measure (PROM) metrics to hospital reimbursement for total hip arthroplasty (THA) and total knee arthroplasty (TKA). Concurrently, the proportion of patients meeting certain PROM metrics at each hospital will be publicly available. Threshold values such as the minimal clinically important difference (MCID) may vary across patient subpopulations. The Centers for Medicare and Medicaid Services proposal to apply blanket threshold values to all hospitals may skew results depending on the population being served. We hypothesized that socioeconomic parameters, such as insurance type, may influence thresholds, such as MCID for the Hip Disability and Osteoarthritis Outcome Score, Joint Replacement (HOOS-JR), and Knee Disability and Osteoarthritis Outcome Score, Joint Replacement (KOOS-JR).

METHODS: There were 852 THA and 1,439 TKA patients who had HOOS-JR and KOOS-JR scores at preoperative and 1-year time points, respectively, and were categorized by payer type: commercial, Medicare (including Medicare Replacement), and Medicaid. The MCID thresholds for each payer were calculated using a distribution-based method (0.5 × SD of H/KOOS-JR) via a bootstrapping procedure with 1,000 iterations per group and random sampling. The results were then compared with both analyses of variance (ANOVA) and Kruskal-Wallis tests.

RESULTS: The mean HOOS-JR bootstrapped MCIDs for commercial, Medicare, and Medicaid were 9.1, 8.9, and 12.6, respectively. Both ANOVA and Kruskal-Wallis tests were statistically significant (P < 0.001). The mean KOOS-JR bootstrapped MCIDs for commercial, Medicare, and Medicaid were 8.8, 9.0, and 11.9, respectively. Both ANOVA and Kruskal-Wallis tests were statistically significant (P < 0.001).

CONCLUSIONS: The MCIDs for HOOS-JR and KOOS-JR are not uniform across payer types. Specifically, Medicaid patients have significantly higher MCIDs following THA and TKA. Applying universal PROM thresholds across heterogeneous patient populations and mandating public reporting of those rates of achieving those thresholds may misrepresent hospitals and providers depending on the subpopulations served.