Background Calprotectin (MRP8/MRP14, S100A8/A9) is a major leukocyte protein previously shown to be associated with disease activity in patients with established rheumatoid arthritis (RA), and some studies indicate that it may be a more accurate measure of joint inflammation than erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP).
Objectives To compare the associations of calprotectin, ESR and CRP to clinical and ultrasound measures of inflammation in patients with early RA, both before and after 12 months of aggressive disease-modifying antirheumatic drug (DMARD) treatment.
Methods RA-patients (n=238) who fulfilled the 2010 ACR/EULAR classification criteria were recruited to the ARCTIC trial between 2010 and 2013. All patients had symptom duration from first swollen joint <2 years and were DMARD-naïve with indication for DMARD treatment. Calprotectin in plasma was analyzed in 217 patients at baseline and 166 patients at 12 months by ELISA. Ultrasound (US) inflammation was evaluated using a standardized protocol with semi-quantitative scoring 0–3 for grey-scale (GS) and power Doppler (PD) in 32 joints (1). Clinical inflammation was assessed by 44 swollen joint count (SJC44), Ritchie Articular Index (RAI), ESR and CRP. Disease activity score (DAS) was calculated. Cross-sectional relationships were assessed by Spearman's correlations.
Results A total of 217 patients were included: 61% female, 71% RF positive, 82% ACPA positive, mean (SD) age 53.5 (13.7) years, mean DAS 3.46 (1.17), median [25, 75 percentile] disease duration 5.7 [2.8, 10.4] months. At 12 months mean DAS was 1.25 (0.72); 74% were in remission according to DAS, 17% low, 9% moderate and 0% high DAS. The median baseline/12 month calprotectin was 1028 [567, 2158]/485 [293, 802] μg/L, ESR 19 [11, 31]/9 [5, 14] mm/h and CRP 7 [3, 18]/3 [1, 5] mg/L. Calprotectin was significantly correlated to clinical, laboratory and US measures of inflammation before treatment onset (table). After 12 months of treatment, calprotectin had a weaker, but statistically significant correlation to US scores, while no association between ESR/CRP and US scores was found.
Conclusions Calprotectin was correlated to inflammation assessed by ultrasound before onset of DMARD treatment, and the association was also present after 12 months of DMARD treatment. The data support that calprotectin might be of interest when assessing disease activity in different stages of RA.
Hammer HB et al Ann Rheum Dis 2011
Acknowledgement We would like to thank Inge Dale at CalproLab and Marianne Eidsheim at Broegelmann Research Laboratory.
Disclosure of Interest M. Jonsson: None declared, H. Hammer Speakers bureau: AbbVie, Roche, Pfizer, UCB, BMS, H. Nordal: None declared, A.-B. Aga: None declared, I. Olsen: None declared, K. Brokstad: None declared, B.-T. Fevang: None declared, T. Kvien Grant/research support from: AbbVie, BMS, MSD, Pfizer, Roche, UCB, Speakers bureau: AbbVie, BMS, Celgene, Celltrion, Eli Lilly, Hospira, Merck-Serono, MSD, Novartis, Orion Pharma, Pfizer, Roche, Sandoz, UCB, S. Lillegraven: None declared, E. Haavardsholm Grant/research support from: AbbVie, MSD, Pfizer, Roche, UCB