Using Patient-Reported Outcomes for Economic Evaluation: Getting the Timing Right

摘要

Background: Patient-reported outcome measures (PROMS) are becoming increasingly popular in orthopedic surgery. Preoperative and postoperative follow-up often elicit PROMS in the form of generic quality-of-life instruments (e.g., Short Form health survey SF-12 SF-12) that can be used in economic evaluation to estimate quality-adjusted life-years (QALYs). However, the timing of postoperative measurement is still under debate. Objectives: To explore the timing of postoperative PROMS collection and the implications for bias in QALY estimation for economic evaluation. Methods: We compared the accuracy of QALY estimation on the basis of utilities derived from the SF-12 at one of 6 weeks, 3 months, 6 months, and 12 months after total knee arthroplasty, under different methods of interpolation between points. Five years of follow-up data were extracted from the St. Vincent's Melbourne Arthroplasty Outcomes (SMART) registry (n = 484). The SMART registry collects follow-up PROMS annually and obtained more frequent outcomes on subset of patients (n = 133). Results: Postoperative PROM collection at 6 weeks, 6 months, or 12 months biased the estimation of QALY gain from total knee arthroplasty by-41 (95 confidence interval CI-59 to-22), 18 (95 CI 4-32), and-8 (95 CI-18 to-2), respectively. This bias was minimized by collecting PROMS at 3 months postoperatively (6 error; 95 CI-9 to 21). Conclusions: The timing of PROM collection and the interpolation assumptions between measurements can bias economic evaluation. In the case of total knee arthroplasty, we recommend a postoperative measurement at 3 months with linear interpolation between preoperative and postoperative measures. The design of economic evaluations should consider timing and interpolation issues.