Development of a score map to guide interpretation of WOMAC Pain scores prior to knee arthroplasty

Abstract

BackgroundScores from patient reported outcome measures (PROMs) are challenging to interpret for both clinicians and patients. PROMs obtained prior to knee arthroplasty (KA) could be used to inform important decisions related to KA made by both patients and clinicians. The purpose of this study was to develop a “score map” to allow for efficient and meaningful use of PROMs scores for patients considering KA. MethodsKnee arthroplasty data obtained between one day and twelve months preoperatively from two multicenter studies were combined and used to develop and test the accuracy of a Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain Scale score map. To develop the score map, individual item scores were used to determine the most probable responses to items for the entire range of possible WOMAC Pain scores. Predicted WOMAC Pain scores, using the most probable response for each possible score on the score map, were compared to actual presurgical WOMAC Pain scores using Weighted Kappa (Κw) agreement coefficients. The score map is an easy-to-use graphical display of the entire range of WOMAC Pain scores from no pain to extreme pain for each item comprising the WOMAC Pain scale. ResultsData from 780 patients were used in the analyses. The score map predicted WOMAC Pain scores and showed substantial agreement with actual WOMAC Pain scores Κw = 0.68 (95 %CI = 0.58, 0.77) to Κw = 0.77 (95 % CI = 0.75, 0.79). Perfect prediction of actual scores occurred between 55.1 % and 62.5 % of the time for all WOMAC Pain items. ConclusionThe WOMAC Pain score map has potential for facilitating a variety of important clinical decisions and discussions between patients and practitioners during healthcare encounters related to KA candidacy. For example, by comparing a patents’ scores to literature-based estimates, patients may better understand how their WOMAC Pain scores compare to other persons who underwent KA, how much a score may change, on average, after surgery and whether this change might be acceptable to them.