Background Calprotectin, a heterodimeric complex of S100A8/9 (MRP8/14), has been demonstrated as an important biomarker of clinical and laboratory disease activity and structural joint damage in rheumatoid arthritis (RA).1,2 Ultrasound is a sensitive and reliable tool for assessing synovial inflammation in RA.3
Objectives To test the hypothesis that calprotectin is associated with clinical and ultrasound disease activity in patients with RA in a cross-sectional study and to investigate the contribution of various parameters to predict ultrasound findings.
Methods A total of 37 patients with RA (24 females, median disease duration 18 months) underwent clinical examination (DAS28) and 7-joint ultrasound score (US-7) of clinically dominant wrist, second and third metacarpophalangeal and proximal interphalangeal, and second and fifth metatarsophalangeal joints to assess synovitis and tenosynovitis by gray-scale (GS) and power Doppler (PD) ultrasound using semiquantitative grading 0-3. The levels of serum calprotectin and C-reactive protein were measured at the time of ultrasound assessment. Clinical and laboratory measures were correlated with ultrasound findings. Multiple regression analysis was used to determine the predictive value of calprotectin, CRP and DAS28 to determine PD synovitis.
Results We found that DAS28 (r=0.605, p<0.001; r=0.605, p<0.001, resp.) and CRP levels (r=0.451, p=0.006; r=0.463, p=0.004, resp.) correlate significantly with GS and PD synovitis. In addition, calprotectin correlated significantly with PD synovitis (r=0.497, p<0.005). Furthermore, serum calprotectin significantly correlated with CRP (r=0.629, p<0.001) and DAS28 (r=0.385, p<0.019). In addition to DAS28 (p=0.001), calprotectin (p<0.001) was a strong predictor of active PD synovitis (adjusted R2=0.811).
Conclusions This study confirms tight association between clinical, laboratory and ultrasound assessment and support circulating calprotectin as an important biomarker for monitoring synovial inflammation in RA.
Andrés Cerezo L, Mann H, Pecha O, et al. Decreases in serum levels of S100A8/9 (calprotectin) correlate with improvements in total swollen joint count in patients with recent-onset rheumatoid arthritis. Arthritis Res Ther. 2011;13(4):R122.
Hammer HB, Fagerhol MK, Wien TN, Kvien TK. The soluble biomarker calprotectin (an S100 protein) is associated to ultrasonographic synovitis scores and is sensitive to change in patients with rheumatoid arthritis treated with adalimumab. Arthritis Res Ther. 2011;13(5):R178.
Backhaus TM, et al. The US7 score is sensitive to change in a large cohort of patients with rheumatoid arthritis over 12 months of therapy. Ann Rheum Dis. 2013 Jul;72(7):1163-9.
Acknowledgements This work was supported by project of MHCR for conceptual development of research organization 023728, IGA grant No. NT12437 and GAUK grant No. 1010213.
Disclosure of Interest None declared