Mylène Jansen

214 Chapter 11 Abstract Background: Knee Image Digital Analysis (KIDA) is standardized radiographic analysis software for measuring osteoarthritis (OA) characteristics. It was validated in mild OA patients, but often used for severe OA as well. The goal of this study was to evaluate the performance of KIDA in severe OA patients. Methods: Of 103 patients, standardized radiographs were performed before and 1 and 2 years after treatment for severe OA. All radiographs were evaluated on subchondral bone density, joint space width (JSW), osteophytes, eminence height, and joint angle, twice within years by the same observer. Part of the radiographs were randomly selected for reevaluation twice within 1 month. The intraclass correlation coefficient (ICC), smallest detectable difference (SDD) and coefficient of variation (CV) were calculated; the SDD and CV were compared to those in mild OA patients. The relation of severity with KIDA parameters and with intra- observer differences was calculated with linear regression models. Results: ICCs were higher in the 98 severe radiographs reanalyzed within 1 month (all >0.8) than the 293 reanalyzed within years (all >0.5; most >0.8). SDDs and CVs were smaller when reanalyzed within a month and generally comparable to those in previous mild OA patients. Some parameters showed significant bias between readings. Severity showed a significant relation with especially osteophytes and JSW parameters, and with the intra-observer variation in these parameters (all p< 0.02). Conclusion: KIDA is a well-performing tool also for severe OA. In order to decrease variability and SDDs, images should be analyzed in a limited time frame and randomized order.