Objective: To develop an additive numerical scoring scheme for the BILAG-2004 index.
Methods: SLE patients were recruited into this multi-centre cross-sectional study. At every assessment, data were collected on disease activity and therapy. Logistic regression was used to model an increase in therapy, as an indicator of active disease, by the BILAG-2004 index score in the nine systems. As both indicate inactivity, scores of D and E were set to 0 and used as the baseline in the fitted model. The models were used to determine the numerical values for Grades A-C. Different scoring schemes were compared.
Results: There were 1510 assessments from 369 SLE patients. The coding schemes suggested for the Classic BILAG index (A = 12, B = 5, C = 1, D/E = 0 and A = 9, B = 3, C = 1, D/E = 0) did not fit the data well. A coding scheme (A = 12, B = 8, C = 1 and D/E = 0) was recommended, based on analysis results and consistency with the numerical coding scheme of the Classic BILAG index.
Conclusion: A reasonable additive numerical scoring scheme based on treatment decision for the BILAG-2004 index is A = 12, B = 8, C = 1, D = 0 and E = 0.