Immunological biomarkers in patients with radiographic axial spondyloarthritis, an exploratory longitudinal Swedish study.

Objectives There is a need for more specific biomarkers to diagnose and predict disease course in patients with axial spondyloarthritis (axSpA). This study aimed to study immunological plasma biomarkers, at different time-points in radiographic (r)-axSpA patients overall and stratified by sex and compare these biomarker pattern in r-axSpA patients concerning disease phenotypes and disease activity. Methods Plasma samples were analysed from r-axSpA patients at and prior (Pre-Backbone) inclusion in the Backbone study. Interferon gamma, interleukin-10, -17A, -17F, -22, -23, -6, MCP-1, TNF-α, VEGF-A, MIF, IgA anti-CD74, zonulin, ESR, hsCRP, white blood cell count, and blood lipids were measured. Results Biomarker pattern discriminated significantly between r-axSpA patients in Backbone and Pre-Backbone compared with controls. When stratifying by sex, it was possible to discriminate between male and female r-axSpA patients in Backbone vs controls and between male r-axSpA patients in pre-Backbone and controls. In Backbone, markers with high discriminative capacity were MIF, IgA anti-CD74, and MCP-1. In Pre-Backbone, IL-6, TNF-α, MIF, triglycerides, cholesterol, IL-10, and zonulin displayed high discriminative capacity. Conclusion Based on their temporal pattern and mutual relationship, we suggest studying MIF, IgA anti-CD74, and MCP-1 in depth, at more time points, to further elucidate disease-driving mechanisms in this complex disease.