Increased blood levels of neutrophil- and platelet-derived markers in patients with radiographic axial spondyloarthritis: a pilot study

A challenge in diagnosing and monitoring radiographic axial spondyloarthritis (r-axSpA) is the absence of reliable biomarkers. This cross-sectional pilot study aimed to evaluate platelet- and neutrophil-derived substances as potential biomarkers in r-axSpA, given the involvement of these cells in disease pathology. Serum and plasma were collected from 13 male, HLA-B27-positive r-axSpA patients without disease-modifying anti-rheumatic drugs and 13 age- and sex-matched blood donor controls. Concentrations of platelet-derived soluble CD40 ligand (sCD40L) and soluble P-selectin (sP-selectin) and neutrophil-derived human neutrophil lipocalin (HNL), myeloperoxidase (MPO), and galectin-3 were measured using ELISA. Associations between these markers and clinical parameters, including C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were assessed by Spearman’s rank correlation. Group differences were analysed using the Wilcoxon signed-rank test. Median concentrations of serum sCD40L (4.2 vs. 2.7 ng/mL; p = 0.001), plasma HNL (23.7 vs. 18.6 mg/L; p = 0.040), serum HNL (74.7 vs. 52.3 mg/L; p = 0.013), and plasma MPO (56.6 vs. 37.3 mg/L; p = 0.027) were significantly higher in r-axSpA patients compared with controls. Plasma HNL correlated positively with CRP and ESR, but not with other clinical parameters. In both patients and controls, serum concentrations of sCD40L, sP-selectin, HNL, and MPO were significantly higher than their plasma counterparts, highlighting differences related to sample processing. Serum sCD40L, serum and plasma HNL, and plasma MPO were elevated in r-axSpA patients compared with controls. These findings warrant validation in larger cohorts to clarify the role of sCD40L, HNL and MPO across a heterogeneous group of patients with early and established r-axSpA.