Serum calprotectin: could it be a biomarker for disease activity and radiological severity in psoriatic arthritis patients under biological therapy?

Abstract Background Psoriatic arthritis (PsA) is a chronic inflammatory arthropathy that gradually damages joints. The pathogenesis of PsA involves immune-mediated chronic inflammation, resulting in tissue damage. Calprotectin (S100A8/A9) (CLP) acts as a proinflammatory factor of innate immunity, thus contributing to chronic inflammatory conditions. Aim of the work To evaluate whether serum CLP could reflect disease activity and pathological findings detected by musculoskeletal ultrasound in PsA patients receiving biological therapy. Patients and methods There were 120 participants in this cohort study: 60 patients with PsA receiving biological therapy for more than three months and 60 healthy controls. The Disease Activity in Psoriatic Arthritis (DAPSA) and the Psoriasis Area and Severity Index (PASI) were used to assess patients with PsA. A human CLP ELISA kit was used to measure serum CLP. Musculoskeletal ultrasound was performed on the dominant site using the PsASon13 composite score to evaluate inflammatory and structural changes. Results The median age of PsA patients was 35 years, and 68.3% of them were female. The PsASon13 imaging score had a median (IQR) of 7.0 (3.0–14.0). Median serum CLP levels were significantly higher in patients compared to controls (1468.4 vs. 1169.7 ng/mL, p < 0.001). ESR levels also revealed a significant difference among groups ( p = 0.005). DAPSA and PsASon13 scores showed a strong positive correlation, and both were significantly correlated with serum CLP ( p < 0.001). PASI score was correlated with DAPSA (rho = 0.494) and SON13 (rho = 0.435) scores ( p < 0.001). ROC curve analysis of serum CLP showed 73.3% sensitivity and 81.7% specificity in differentiating PsA patients from controls at an optimal cut-off value of 1285 ng/mL. Conclusions Serum CLP is a promising biomarker for monitoring disease activity in PsA, reflecting both clinical and ultrasound-assessed inflammation, and may aid management of patients on biologic therapy.