Measurement of disease activity in systemic lupus erythematosus. Prospective validation of 3 clinical indices.

Several clinical indices have been proposed to measure disease activity in patients with systemic lupus erythematosus. Only a few have been subjected to extensive analysis. We report a methodological comparison of reliability, validity, responsiveness, and feasibility of the Lupus Activity Criteria Count, the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), and our own simplified modification of the latter (MEX-SLEDAI). They were applied prospectively to 39 patients with diverse degrees of disease activity in 3 consecutive visits. Inter-observer reliability outweighed experts' evaluation (rs = 0.86 to 0.89, p < 0.0001 versus 0.74). Significant association was demonstrated between indices and experts' judgment, managing physician's opinion, changes in treatment and clinical course. Moreover, indices showed good convergent validity (rs = 0.76 to 0.79, p < 0.0001), and responsiveness. MEX-SLEDAI was the least expensive instrument.