Calprotectin may be useful marker of inflammation in early rheumatoid arthritis
Calprotectin appears to be associated with clinical measures of disease activity and ultrasound inflammation in treatment-naïve patients with rheumatoid arthritis (RA), a study has found.
Researchers examined 215 RA patients (mean age 50.9 years; 61 percent female) who were naïve to disease-modifying antirheumatic drug (DMARD). Using plasma samples, calprotectin was evaluated at baseline and after 1, 3 and 12 months. All patients received treat-to-target therapy.
Majority (82 percent) of the patients were anticitrullinated peptide antibody positive, and the median symptom duration was 5.8 months. In multivariate logistic regression models, calprotectin significantly correlated with Clinical Disease Activity Index (r=0.32), erythrocyte sedimentation rate (ESR; r=0.50) and ultrasonography power Doppler (r=0.42) before DMARD initiation.
After 12 months of treatment, only calprotectin remained significantly correlated with power Doppler (r=0.27).
Levels of calprotectin, ESR and CRP at baseline did not predict treatment response, although high levels of calprotectin were found to be associated with radiographic progression.
The present data suggest that calprotectin may be of interest as an inflammatory marker to assess disease activity in different stages of RA, particularly at treatment onset and in patients in clinical remission, researchers noted.
However, more studies are needed to evaluate the clinical relevance of calprotectin as a marker of inflammation, they added.
A calcium-binding leucocyte protein consisting of the heterocomplex of S100A8/ A9 (myeloid-related protein, MRP8/MRP14), calprotectin is classified as a damage-associated molecular pattern molecules, reported to be highly elevated in various immune-mediated inflammatory diseases, and is a validated marker of disease activity in inflammatory bowel diseases. [Nat Med 2010;16:713–7]
Expressed in granulocytes and monocytes, predominantly at the sites of inflammation, calprotectin has also been detected in macrophages and fibroblast-like synoviocytes of the synovium in RA. In previous studies, calprotectin concentrations in plasma have been shown to have good correlations with the synovial fluid. Moreover, calprotectin levels appear to be higher in patients with RA than in those with osteoarthritis or spondyloarthritis. [Rheumatology 2013;52:2177–86; Arthritis Res Ther 2006;8:R69]