ORIGINAL PAPER Evaluating change using patient-reported outcome measures in knee replacement: the complementary nature of the EQ-5D index and VAS scores Fang-Ju Lin • Jennifer Samp • Alexis Munoz • Pei Shieen Wong • A. Simon Pickard Received: 2 February 2013 / Accepted: 6 May 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract Purpose Using the UK National Health Service’s Patient Reported Outcome Measures data, we examined the mag- nitude of changes and relationship among the EQ-5D index, EQ-5D Visual Analog Scale (EQ-VAS), and Oxford Knee Score (OKS) in patients undergoing knee replacement. Methods Patients undergoing knee replacements in 2009–2011 completed the EQ-5D and OKS before and after surgery. Responsiveness was compared using the standard- ized response mean (SRM). Stratified analyses based on change scores in the OKS were utilized to investigate how changes in the outcome measures related to each other. Patients were grouped based on the preoperative OKS to examine the relationship of change in the EQ-5D index and EQ-VAS with respect to initial health status. Results For the overall cohort (54,486 patients), mean change scores pre/post knee replacement were 0.30 for the EQ-5D index (SD 0.33; SRM = 0.90), 3.3 for the EQ-VAS (SD 21.0; SRM = 0.16), and 14.9 for the OKS (SD 9.9; SRM = 1.50). The OKS changed uniformly with the EQ- 5D index, but less concordantly with the EQ-VAS in response to knee replacement surgery. Substantial func- tional improvement was needed before mean EQ-VAS change scores showed improvement. Patients with worse preoperative health status had greater improvement fol- lowing surgery, but the improvement in the EQ-5D index did not necessarily translate into comparable improvement in self-perceived well-being measured by the EQ-VAS. Conclusions On average, patients self-rated their health systematically lower using the EQ-VAS compared to the EQ- 5D index and OKS following knee replacement. The EQ-VAS captured information about how patients feel about their health pre-/post-surgical intervention that contrasted with more functional measures of health. Additional qualitative research is needed to better understand these differences. Keywords EQ-5D Á EQ-VAS Á Knee replacement Á Oxford Knee Score JEL Classification I10 This study was presented at the Midwest Social and Administrative Pharmacy Conference, 8–10 August 2012, Madison, WI, USA, and at the 19th Annual Conference of the International Society for Quality of Life Research, 24–27 October 2012, Budapest, Hungary. An earlier draft of this manuscript was presented as a discussion paper at the EuroQol Group Scientific Plenary Meeting in Rotterdam, The Netherlands, in September, 2012. Electronic supplementary material The online version of this article (doi:10.1007/s10198-013-0489-9) contains supplementary material, which is available to authorized users. F.-J. Lin Á J. Samp Center for Pharmacoepidemiology and Pharmacoeconomic Research, Department of Pharmacy Systems, Outcomes and Policy, College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA A. Munoz Department of Community Health Sciences, School of Public Health, University of Illinois at Chicago, Chicago, IL, USA P. S. Wong College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA A. S. Pickard (&) Center for Pharmacoepidemiology and Pharmacoeconomic Research, Department of Pharmacy Systems, Outcomes and Policy, College of Pharmacy, University of Illinois at Chicago, 833 South Wood St., Room 287, Chicago, IL 60612, USA e-mail: pickard1@uic.edu 123 Eur J Health Econ DOI 10.1007/s10198-013-0489-9