Background MRP8/14 (also known as calprotectin) has been widely studied as potential predictor of disease activity and response to treatment in inflammatory diseases. In Juvenile Idiopathic Arthritis (JIA), MRP8/14 levels are highly predictive of disease flares in systemic JIA. In a more heterogeneous group of JIA patients (pts), MRP8/14 levels have been shown to predict response to MTX. High levels of baseline MRP8/14 are associated with good response to anti-TNF treatment, whereas elevated MRP8/14 levels at time of discontinuation are associated with higher chance to flare. In clinical practice, ultrasound could be usefull to define the state of disease activity. Indeed, PD-US assessment of synovial vascularization has been shown to be more sensitive than serum markers of inflammation in the identification of active disease in JIA.
Objectives To explore the association between calprotectin, clinical and US assessment in JIA pts.
Methods A total of 30 consecutive pts (aged under 18 years) with oligo or poly JIA were assessed by US, clinical examination and MRP8/14 serum levels. Serum MRP8/14 was measured by ELISA in all pts and in 20 age matched healthy controls. Ultrasonographic B-mode and power Doppler assessment of 44 joints each pts were performed. Patients were evaluated using Wallace criteria.
Results 30 consecutive non systemic JIA pts (F 18) were evaluated: 13 persistent and 8 extended oligoarticular, 6 polyarticular (1 RF positive), 2 ERA, 1 psoriatic JIA. Median age at disease onset was 10.6 yrs (mean 10.8, range 2–16). Mean disease duration was 5.4 yrs (range 0.1–15.9). Mean active joints was 2 (range 0–26). 14 pts were active according to Wallace criteria and 16 pts were active according to US evaluation. Ultrasonographic B-mode and power Doppler assessment was significantly correlated with clinical examination (Mcnemar test p=0.683, Cohen's K 0.602). The majority of our enrolled pts were in phase of oligoarticular involvement with minimal disease activity (median active joints=0). No statistically significant difference in serum MRP8/14 was found between all JIA pts and healthy controls (p=0.33). No statistically significant difference in serum MRP8/14 was found between active (according to clinical examination) JIA pts and healthy controls (p=0.69) and between inactive JIA pts and healthy control (p=0.23). Concentrations of MRP8/14 in active and inactive pts according to Wallace were not significantly different (p=0.75). No statistically significant difference in serum MRP8/14 was found between active and inactive pts according to US assessment (0.85). Only 6 pts (4 out of 6 with polyarticular course) showed calprotectin levels higher than normal. We found a correlation between calprotectin and CRP (Spearman r 0.4380, p=0.01) and between calprotectin and ESR (Spearman r 0.3800, p=0.05).
Conclusions To our knowledge this is the first study to examine the correlation between MRP8/14 levels, clinical and US assessment in JIA. Serum levels of MRP8/14 (a biomarker of activation of the innate immune system) are not significatively different in oligoarticular JIA from healthy controls. Calprotectin high levels, could be related with a poliarticular disease either in clinical activity or in subclinical remission. However our study need to be extended to a larger number of pts followed prospectively.
Disclosure of Interest None declared