Development and validation of the BILAG-2004 index for the assessment of disease activity in systemic lupus erythematosus.

This research to develop and validate the BILAG-2004 index for the assessment of disease activity in patients with [systemic lupus erythematosus] SLE had involved several validation studies. The reliability of this index was shown in 2 exercises, as assessed by level of agreement, kappa statistic, ICC and disagreement between physicians. This study also highlighted the importance of training in ensuring optimal performance of the index. This index had construct validity as higher scores in the index were significantly associated increasing ESR, decreasing C3, decreasing C4, elevated anti-dsDNA antibody and increasing SLEDAI-2000 scores. Active disease scores were significantly associated with increase in therapy, confirming the criterion validity of the index. Sensitivity to change was demonstrated as changes in the score of the index were differentially related to change in therapy, with greater change in score having greater predictive power. Rasch analysis showed that this index had a good fit to the Rasch model, indicating that it is a unidimensional ordinal scale index with internal construct validity. The validation studies led to revisions of the index to ensure it had face and content validity. The results of this research have shown that the revised BILAG-2004 index is valid for use to assess SLE disease activity.