| Sumario: | * STUDY DESIGN: Clinical measurement study. * BACKGROUND: Computer adaptive testing (CAT) methods may allow detection of change across the continuum of osteoarthritis (OA) care. * OBJECTIVE: To evaluate the sensitivity to change of a self-report OA CAT instrument (OA-CAT) following surgery. * METHODS: Core measures consisted of the 5-item OA-CAT function, pain, and disability scales; the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC); the University of California at Los Angeles activity rating scale; and the Medical Outcomes Study 12-Item Short-Form Health Survey (SF-12), which were administered in 3 samples. Fifty-three patients with hip dysplasia completed the core measures, the Hip disability and Osteoarthritis Outcome Score physical function short form (HOOS-PS), and the Modified Harris Hip Score (MHHS) before periacetabular osteotomy, and at 6 months, 1 year, and 2 years after periacetabular osteotomy. The hip (n = 62) and knee (n = 66) arthroplasty samples completed core measures and the MHHS or the Knee Society's Knee Scoring System at baseline and at 3-month follow-up. Mean change, floor and ceiling effects (percent), and effect size were calculated. * RESULTS: For osteotomy, the 6-month physical function effect sizes for the OA-CAT, WOMAC, HOOS-PS, MHHS, and SF-12 physical component summary scores were 0.66 (95% confidence interval [CI]: 0.08, 1.61), 0.78 (95% CI: 0.56, 1.10), 0.91 (95% CI: 0.70, 1.21), 0.64 (95% CI: 0.22, 1.07), and 0.87 (95% CI: 0.53, 1.38), respectively. Effect-size trends were all increased at 1 year, and most were level at 2 years. For hip arthroplasty, the OA-CAT, WOMAC, MHHS, and SF-12 effect sizes were 1.27 (95% CI: 0.88, 1.84), 1.50 (95% CI: 1.20, 1.80), 0.68 (95% CI: 0.35, 1.04), and 0.56 (95% CI: 0.29, 0.88), respectively. For knee arthroplasty, the OA-CAT, WOMAC, Knee Society Knee Scoring System, and SF-12 effect sizes were 0.81 (95% CI: 0.56, 1.14), 0.85 (95% CI: 0.61, 1.10), 0.09 (95% CI: -0.22, 0.40), and -0.01 (95% CI: -0.39, 0.31), respectively. The OA-CAT and SF-12 demonstrated smaller ceiling effects than the HOOS-PS and other instruments, especially at 1 and 2 years. Administration time was less for the OA-CAT than for the WOMAC physical function subscale. * CONCLUSION: The OA-CAT shows potential for outcome measurement after hip and knee surgery. Larger studies are needed to better understand relative performance.
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