Serum calprotectin (S100A8/9), clinical and ultrasound assessment in patients with juvenile idiopathic arthritis.

Objectives: To explore the association between serum S100A8/9 (calprotectin), clinical and ultrasound (US) assessment in juvenile idiopathic arthritis (JIA) patients.

Methods: A total of 30 well-characterised consecutive patients (18 female) with non-systemic JIA and 20 age-matched healthy controls were included. Serum and plasma samples obtained the same day of the clinical and sonographical assessment were tested for calprotectin levels by ELISA. Clinical status was defined using Wallace criteria. Ultrasonographic B-mode and power Doppler (PD) assessment of 44 joints for each subject was performed.

Results: Clinically active disease was present in 14 patients, while 16 patients were active according to US evaluation. We found no differences in the serum/plasma calprotectin levels in clinically active disease group [29.6 (5.4-198.1) ng/ml; 12.6 (2.8-65.8) ng/ml] as compared with inactive disease group [24.8 (14.1-204.3); 12.7 (3.4-65.1)] (p=0.73; p=0.29). There was also no difference between US active disease [29.8 (5.4-204.3); 12.9 (2.8-65.8)] and US inactive disease [24.8 (12.1-197.1); 11.7 (3.4-44.2)] with regard to the serum/plasma calprotectin levels (p=0.83; p=1.0). Serum/plasma calprotectin levels correlated moderately with C-reactive protein (CRP) (Spearman r=0.44, p=0.01; Spearman r=0.56, p=0.0021).

Conclusions: To our knowledge, this is the first study to simultaneously examine the correlation between serum/plasma calprotectin levels, clinical and US assessment in JIA. Calprotectin was not associated with the disease status in JIA patients with low number of active joints and its levels were moderately correlated with CRP. Our preliminary study needs to be extended with a larger number of patients.