Performance of systemic lupus erythematosus responder index for detecting clinician‐rated responders in patients with active systemic lupus erythematosus

OBJECTIVE: Disease activity measures in systemic lupus erythematosus (SLE) are critical tools for trial endpoints. We aimed to evaluate the performance of current treatment outcome measures in SLE. METHODS: Individuals with active SLE with a clinical SLE Disease Activity Index-2000 (SLEDAI-2K) score of at least 4 were followed up for two or more visits and classified as responders and non-responders based on a physician's judgment of improvement. The treatment outcome measures including SLEDAI-2K responder index-50 (SRI-50), SLE responder index-4 (SRI-4), substituting SLEDAI-2K with SRI-50 in SRI-4 (SRI-4(50)), SLE Disease Activity Score (SLE-DAS) responder index (Δ ≥ 1.72) and the British Isles Lupus Assessment Group (BILAG)-based Composite Lupus Assessment (BICLA) were tested. The performance of those measures was shown by sensitivity, specificity, predictive value, positive likelihood ratio, accuracy, and agreement against a physician-rated improvement. RESULTS: Twenty-seven patients with active SLE were followed. The total cumulative pair of visits (baseline and follow up) was 48. The overall accuracies (95% confidence interval [CI]) of SRI-50, SRI-4, SRI-4(50), SLE-DAS, and BICLA for detecting responders in all patients were 72.9 (58.2-84.7), 75.0 (60.4-86.4), 72.9 (58.2-84.7), 75.0 (60.4-86.4), and 64.6 (49.5-77.8), respectively. Subgroup analyses of lupus nephritis (23 patients had a pair of visits) found the accuracies (95% CI) of SRI-50, SRI-4, SRI-4(50), SLE-DAS, and BICLA were 82.6 (61.2-95.0), 73.9 (51.6-89.8), 82.6 (61.2-95.0), 82.6 (61.2-95.0), and 78.3 (56.3-92.5), respectively. However, there were no significant differences between the groups (P > 0.05). CONCLUSION: SRI-4, SRI-50, SRI-4(50), SLE-DAS responder index, and BICLA demonstrated comparable abilities to identify clinician-rated responders in patients with active SLE and lupus nephritis.