# Evaluation of Serum Calprotectin Levels and Their Relationship with Disease Activity in Psoriatic Arthritis and Axial Spondyloarthritis

## TL;DR

Serum calprotectin levels are higher in psoriatic arthritis patients and linked to disease activity, but not in axial spondyloarthritis.

## Contribution

Identifies serum calprotectin as a potential biomarker for disease activity in psoriatic arthritis but not in axial spondyloarthritis.

## Key findings

- Calprotectin levels were significantly higher in PsA and AxSpA patients compared to healthy controls.
- In PsA, calprotectin correlated with disease activity indices like ASDAS-CRP and DAS28-CRP.
- Calprotectin showed poor association with disease activity in AxSpA patients.

## Abstract

Background and Objectives: Psoriatic arthritis (PsA) is a chronic inflammatory arthritis characterized by marked clinical heterogeneity and variable disease trajectories, underscoring the need for robust biomarkers of inflammatory burden. Serum calprotectin, a neutrophil- and monocyte-derived protein, has been proposed as a surrogate marker of active inflammation in inflammatory arthritis due to its close association with innate immune activation. In this study, we compare serum calprotectin levels among patients with PsA, axial spondyloarthritis (AxSpA), and healthy controls and evaluate their association with disease activity. Materials and Methods: This single-center, cross-sectional study included 123 patients with PsA, 119 patients with AxSpA, and 77 healthy controls. Serum calprotectin levels were measured by enzyme-linked immunosorbent assay, and their associations with disease activity were evaluated using correlation, multivariable regression, and receiver operating characteristic analyses. Results: Serum calprotectin levels were significantly higher in PsA and AxSpA patients compared with healthy controls (p < 0.001 for both) and were higher in PsA than in AxSpA (p = 0.022). In PsA, serum calprotectin levels showed significant correlations with ASDAS-CRP, DAS28-CRP, and DLQI, but not with CRP or ESR. In contrast, in AxSpA, calprotectin showed only a weak association with CRP and was not related to disease activity indices. In multivariable analysis, serum calprotectin was independently associated with ASDAS-CRP in PsA (B = 0.704, p = 0.003), but not in AxSpA. Receiver operating characteristic analysis demonstrated that serum calprotectin discriminated high disease activity in PsA with an area under the curve of 0.669 (95% CI: 0.563–0.775; p = 0.003). Conclusions: Serum calprotectin levels are elevated in patients with PsA and are associated with disease activity, supporting its potential role as a biomarker in this condition. In contrast, serum calprotectin does not appear to reflect disease activity in AxSpA, suggesting disease-specific differences in its clinical utility.