To evaluate radiographic progression and the relationship of radiologic scores obtained by the Genant and Larsen methods in a clinical trial of recombinant human interleukin‐1 receptor antagonist (IL‐1Ra).

Patients with rheumatoid arthritis (RA) were randomized into 4 groups: placebo (n = 121) or IL‐1Ra at a daily dosage of 30 mg (n = 119), 75 mg (n = 116), or 150 mg (n = 116). Hand radiographs obtained at baseline, 24 weeks, and 48 weeks were scored using both methods.

At 24 weeks, by the Genant method, there was significant reduction in the score for progression of joint space narrowing (JSN) and the total score (a combination of erosion and JSN) in all treatment groups. Least‐squares mean changes in the Genant erosion score from baseline to 24 weeks were significantly reduced after treatment with IL‐1Ra at 30 mg/day and for all IL‐1Ra treatment groups combined. The changes corresponded to a reduction of 38% in erosion, 58% in JSN, and 47% in total score. Patients treated with IL‐1Ra at 75 mg/day had a significant reduction in the Larsen erosive joint count (LEJC), and all IL‐1RA–treated groups combined showed a 45% reduction. Correlations (r) between the Genant total and Larsen scores were 0.84 at baseline, 0.83 at week 24, and 0.83 at week 48 (P < 0.0001); correlations between the Genant erosion score and the LEJC were 0.83 (P < 0.0001) at all visits; correlations between the Genant total and the Larsen scores were 0.32 and 0.49 (P < 0.0001) for progression from baseline to week 24 and from baseline to week 48, respectively; correlations between the Genant erosion score and the LEJC were 0.36 and 0.41 (P < 0.0001) for progression to weeks 24 and 48, respectively.

IL‐1Ra reduced radiologic progression of RA. Scores by the 2 methods correlated strongly for each individual time point, but much less strongly for assessments of disease progression.