Autoantibody and biomarker detection in the follow-up of autoimmune diseases: state of the art and future perspectives.

Originally developed for the diagnosis of autoimmune diseases, the application of autoantibodies and related biomarkers has been extended in certain cases to monitor therapeutic efficacy and to predict disease recurrence and/or severity. Several critical considerations must be addressed prior to employing autoantibodies for monitoring purposes: (i) whether the autoantibody is pathogenic, as exemplified by anti-glomerular basement membrane and anti-acetylcholine receptor autoantibodies; (ii) whether the autoantibody level is essential for tracking disease activity, which may necessitate establishing prognostic thresholds and/or adapting detection methodologies; (iii) whether there is added value in combining autoantibodies, as demonstrated with anti-dsDNA and anti-chromatin antibodies in systemic lupus erythematosus; (iv) which immunoglobulin isotype is optimal for monitoring; and (v) whether alternative biomarkers exist that provide greater accuracy for patient follow-up. Additional issues remain unresolved, including appropriate intervals between measurements, intra- and inter-laboratory reproducibility, inter-assay variations, and ethnic variability, among others. To address these challenges, the European Autoimmunity Standardization Initiative (EASI) has proposed adapted strategies for utilizing autoantibodies in the longitudinal assessment of selected autoimmune diseases, as presented in this special issue.