An update on biomarker discovery and use in axial spondyloarthritis.

Evaluation of diagnosis, disease activity, and risk for joint damage all represent important unmet clinical needs in the management of axial spondyloarthritis that have been explored using biomarkers. Areas covered: This review used the search terms biomarkers, ankylosing spondylitis, spondyloarthritis, spondyloarthropathy, pathogenesis, genetics, diagnostic tools, prognosis, to explore advances in biomarker development relevant to unmet clinical needs. Expert commentary: Despite major advances in the identification of genetic risk markers, HLA-B*27 remains the only marker with clinical utility for diagnostic purposes. Serological antibody to class II-associated invariant chain peptide (CLIP) requires further validation. A substantial array of biomarkers related to inflammatory processes and cartilage and bone remodeling have been evaluated using established clinical tools as well as new MRI-based outcomes for disease activity. Beyond C-reactive protein (CRP), none have demonstrated substantial associations with these parameters to justify clinical use and high priority candidates for further validation have not been identified. Leading candidates for further validation studies of prognostic biomarkers are metalloproteinases (MMP), calprotectin, adipokines, MMP-degraded citrullinated fragments of connective tissue proteins such as vimentin, and factors that regulate MMP expression. New approaches have explored combinations of targeted biomarkers and metabolomics analyses to identify optimal profiles of biomarkers related to the clinical endpoint of interest.