Sensitivity to Change of a Computer Adaptive Testing Instrument for Outcome Measurement After Hip and Knee Arthroplasty and Periacetabular Osteotomy.

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. J Orthop Sports Phys Ther 2016;46(9):756-767. Epub 5 Aug 2016. doi:10.2519/jospt.2016.6442.