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

## TL;DR

This paper reviews the use of autoantibodies and biomarkers for monitoring autoimmune diseases and outlines challenges and strategies for their effective application.

## Contribution

The paper presents strategies from the European Autoimmunity Standardization Initiative (EASI) for improving autoantibody monitoring in autoimmune diseases.

## Key findings

- Autoantibodies can monitor disease activity and predict recurrence in some autoimmune diseases.
- Combining autoantibodies, like anti-dsDNA and anti-chromatin, improves monitoring accuracy in systemic lupus erythematosus.
- Standardization efforts are needed to address variability in autoantibody measurements and improve reproducibility.

## Abstract

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.