Jonsson MK, et al. – The researchers examined calprotectin as a marker of inflammation in patients with early rheumatoid arthritis (RA). Investigations demonstrated that calprotectin was associated with inflammation evaluated by ultrasound before and during disease–modifying antirheumatic drug (DMARD) treatment, and was also associated with radiographic progression. These findings indicated that calprotectin could be used as an inflammatory marker for evaluating disease activity in different stages of RA.

Methods

• At baseline, and after 1, 3 and 12 months, plasma from disease–modifying antirheumatic drug (DMARD)–naïve patients with RA fulfilling 2010 American College of Rheumatology/European League Against Rheumatism classification criteria with symptom duration <2 years was evaluated for calprotectin.
• As part of a randomised controlled strategy trial (ARCTIC), all patients received treat–to–target therapy.
• By correlations, the association between calprotectin, erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) and measures of disease activity were evaluated.
• The likelihood ratios and logistic regression models were used to evaluate the predictive value of the baseline inflammatory markers for treatment response and radiographic damage.

Results

• 215 patients were included: 61% female, 82% anti–citrullinated peptide antibody positive, mean (SD) age 50.9 (13.7) years and median (25, 75 percentile) symptom duration 5.8 (2.8, 10.5) months. 
• Findings suggested that calprotectin was significantly correlated with Clinical Disease Activity Index (r=0.32), ESR (r=0.50) and ultrasonography power Doppler (r=0.42) before treatment onset.
• After 12 months of treatment, calprotectin, but not ESR and CRP, was significantly correlated with power Doppler (r=0.27).
•  Baseline levels of calprotectin, ESR and CRP were not predictive of treatment response.
• However, high levels of calprotectin were associated with radiographic progression in multivariate models.