title: The Impact of Regression to the Mean on Economic Evaluation in Quasi-Experimental Pre-Post Studies: The Example of Total Knee Replacement Using Data from the Osteoarthritis Initiative.
abstract: Many treatments are evaluated using quasi-experimental pre-post studies susceptible to regression to the mean (RTM). Ignoring RTM could bias the economic evaluation. We investigated this issue using the contemporary example of total knee replacement (TKR), a common treatment for end-stage osteoarthritis of the knee. Data (n = 4796) were obtained from the Osteoarthritis Initiative database, a longitudinal observational study of osteoarthritis. TKR patients (n = 184) were matched to non-TKR patients, using propensity score matching on the predicted hazard of TKR and exact matching on osteoarthritis severity and health-related quality of life (HrQoL). The economic evaluation using the matched control group was compared to the standard method of using the pre-surgery score as the control. Matched controls were identified for 56% of the primary TKRs. The matched control HrQoL trajectory showed evidence of RTM accounting for a third of the estimated QALY gains from surgery using the pre-surgery HrQoL as the control. Incorporating RTM into the economic evaluation significantly reduced the estimated cost effectiveness of TKR and increased the uncertainty. A generalized ICER bias correction factor was derived to account for RTM in cost-effectiveness analysis. RTM should be considered in economic evaluations based on quasi-experimental pre-post studies. Copyright © 2017 John Wiley & Sons, Ltd.
authors.affiliation: Centre for Health Policy, School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia.|The University of Melbourne Department of Surgery, St. Vincent's Hospital, Melbourne, VIC, Australia.
authors.forename: Chris
authors.initials: C
authors.lastname: Schilling
authors.affiliation: Centre for Health Economics, Monash Business School, Monash University, Melbourne, VIC, Australia.
authors.forename: Dennis
authors.initials: D
authors.lastname: Petrie
authors.affiliation: The University of Melbourne Department of Surgery, St. Vincent's Hospital, Melbourne, VIC, Australia.|Department of Orthopaedics, St. Vincent's Hospital, Melbourne, VIC, Australia.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Dowsey
authors.affiliation: The University of Melbourne Department of Surgery, St. Vincent's Hospital, Melbourne, VIC, Australia.|Department of Orthopaedics, St. Vincent's Hospital, Melbourne, VIC, Australia.
authors.forename: Peter F
authors.initials: PF
authors.lastname: Choong
authors.affiliation: Centre for Health Policy, School of Population and Global Health, The University of Melbourne, Carlton, VIC, Australia.
authors.forename: Philip
authors.initials: P
authors.lastname: Clarke
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000191:economics*; D003362:Cost-Benefit Analysis; D016208:Databases, Factual; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015233:Models, Statistical; D020370:Osteoarthritis, Knee / Q000191:economics / Q000601:surgery*; D011788:Quality of Life
keywords: economic evaluation; health-related quality of life; quasi-experimental design; regression to the mean; total knee replacement