Ultrasensitive serum interferon alpha equals interferon signatures as a marker of lupus disease activity.

Type 1 interferon-alpha gene expression signatures have long served as surrogate markers of pathway activity in systemic lupus erythematosus, but recent ultrasensitive assays now allow direct quantification of circulating interferon-alpha. In this cross-sectional study of 252 patients with systemic lupus erythematosus, serum interferon-alpha was measured by single molecule array, and 51 interferon scores were derived from 72 transcripts analyzed by Nanostring. Both serum interferon-alpha and interferon scores showed only modest associations with disease features, but serum interferon-alpha correlated more strongly with disease activity than most interferon scores and better discriminated remission and low disease activity states. These findings indicate that direct measurement of circulating interferon-alpha may provide clinically useful information and could be at least comparable to, and in some respects more informative than, interferon signatures for assessing disease status.