Sensitivity-to-change and validity of semi-automatic joint space width measurements in hand osteoarthritis: a follow-up study

Objective To assess sensitivity-to-change and validity of longitudinal quantitative semi-automatic joint space width (JSW) measurements and to compare this method with semi-quantitative joint space narrowing (JSN) scoring in hand osteoarthritis (OA) patients. Design Baseline and 2-year follow-up radiographs of 56 hand OA patients (mean age 62 years, 86% women) were used. JSN was scored 0–3 using the Osteoarthritis Research Society International atlas and JSW was quantified in millimetres (mm) in the second to fifth distal, proximal interphalangeal and metacarpal joints (DIPJs, PIPJs, MCPJs). Sensitivity-to-change was evaluated by calculating Standardized Response Means (SRMs). Change in JSW or JSN above the Smallest Detectable Difference (SDD) defined progression on joint level. To assess construct validity, progressed joints were compared by cross-tabulation and by associating baseline ultrasound variables with progression (using generalized estimating equations, adjusting for age and sex). Results The JSW method detected statistically significant mean changes over 2.6 years (−0.027 mm (95%CI −0.01; −0.04), −0.024 mm (−0.01; −0.03), −0.021 mm (−0.01; −0.03) for DIPJs, PIPJs, MCPJs, respectively). Sensitivity-to-change was low (SRMs: 0.174, 0.168, 0.211, respectively). 9.1% (121/1336) of joints progressed in JSW, but 3.6% (48/1336) widened. 83 (6.2%) joints progressed in JSW only, 36 (2.7%) in JSN only and 37 (2.8%) in both methods. Progression in JSW showed weaker associations with baseline inflammatory ultrasound features than progression in JSN. Conclusions Assessment of progression in hand OA defined by JSW measurements is possible, but performs less well than progression defined by JSN scoring. Therefore, the value of JSW measurements in hand OA clinical trials remains questionable.