Novel Biomarker of Collagen Degradation can Identify Patients Affected with both Axial Spondyloarthritis and Crohn's Disease

Objective Chronic inflammatory arthritis is a hallmark of axial spondyloarthritis (axSpA), where co-existence of Crohn's Disease (CD) is prominent. We investigated the association between biomarkers of collagen degradation in healthy controls (HC) and patients with axSpA, CD and CD-axSpA overlap, with the aim to investigate the biomarkers' ability to identify patients with CD-axSpA overlap.

Methods Patients with axSpA fulfilling ASAS criteria (n=13), biopsy-proven CD (n=14), subjects with axSpA and CD overlap (n=10) and healthy controls (n=11) undergoing standard of care colonoscopies were included in the study. The collagen biomarkers measuring type III, IV, VI and X collagen (C3M, C4M, C6M and C10C, respectively) were measured in plasma samples from all subject groups. Statistical analysis was performed using an ANCOVA adjusted for age, an AUROC analysis and spearman correlations.

Results C4M was significantly higher in patients with CD-axSpA overlap compared to axSpA, CD and HCs (all p<0.0001). In an AUROC analysis, C4M showed a complete separation between the patients with CD-axSpA overlap compared to HC, axSpA and CD with an AUC=1.00; p=0.0001. No differences were found between the patient groups for C3M, C6M and C10C. No correlations were found between the collagen biomarkers and CRP, BASDAI, SCCAI or HBI scores.

Conclusion Degradation of type IV collagen quantified by C4M showed a complete separation of patients with CD-axSpA overlap, compared to axSpA, CD and HC patients, which indicates an excessive collagen degradation and epithelial turnover. This biomarker could potentially be used to identify patients affected by both manifestations, and guide treatment decisions.