Yee CS et al. (2007) British Isles lupus assessment group 2004 index is valid for assessment of disease activity in systemic lupus erythematosus. Arthritis Rheum 56: 4113–4119

In a multicenter, cross-sectional study, Yee et al. have determined the construct and criterion validity of the British Isles Lupus Assessment Group 2004 index (BILAG-2004), a revision of the Classic BILAG index for disease activity in systemic lupus erythematosus (SLE). BILAG-2004 measures disease activity (scored from A to E) in nine systems: constitutional, mucocutaneous, neuropsychiatric, musculoskeletal, cardiorespiratory, gastrointestinal, ophthalmic, renal and hematologic. The index produces an overview of disease activity rather than a global score; where necessary, the highest score obtained on any of the systems assessed is taken as the overall score.

The study included 369 patients with SLE, from whom a total of 1,510 disease activity assessments were obtained. Increasing overall BILAG-2004 scores were associated with increasing erythrocyte sedimentation rate, decreasing C3 and C4 levels, increasing anti-double-stranded DNA antibody levels, and increasing SLE Disease Activity Index 2000 scores, demonstrating construct validity. Increase in therapy was more frequent for patients with higher BILAG-2004 scores, and scores indicating active disease (overall score of A or B) were significantly associated with increase in therapy, demonstrating criterion validity. Sensitivity, specificity, and positive and negative predictive values of BILAG-2004 were comparable to those of the classic BILAG index.

The authors conclude that the BILAG-2004 index is a valid measure of SLE disease activity, and recommend its adoption for clinical trials and outcome studies in SLE.