Introduction: Approximately 30 % of juvenile idiopathic arthritis (JIA) patients fail to respond to anti-TNF treatment. When clinical remission is induced, some patients relapse after treatment has been stopped.We tested the predictive value of MRP8/14 serum levels to identify responders to treatment and relapse after discontinuation of therapy.Methods: Samples from 88 non-systemic JIA patients who started and 26 patients who discontinued TNF-blockers were analyzed.MRP8/14 serum levels were measured by in-house MRP8/14 ELISA and by Bühlmann Calprotectin ELISA at start of anti-TNF treatment, within 6 months after start and at discontinuation of etanercept in clinical remission.Patients were categorized into responders (ACRpedi ≥ 50 and/or inactive disease) and non-responders (ACRpedi < 50) within six months after start, response was evaluated by change in JADAS-10.Disease activity was assessed within six months after discontinuation.Results: Baseline MRP8/14 levels were higher in responders (median MRP8/14 of 1466 ng/ml (IQR 1045-3170)) compared to non-responders (median MRP8/14 of 812 (IQR 570-1178), p < 0.001).Levels decreased after start of treatment only in responders (p < 0.001).Change in JADAS-10 was correlated with baseline MRP8/14 levels (Spearman's rho 0.361, p = 0.001).Patients who flared within 6 months after treatment discontinuation had higher MRP8/14 levels (p = 0.031, median 1025 ng/ml (IQR 588-1288)) compared to patients with stable remission (505 ng/ml (IQR 346-778)).Results were confirmed by Bühlmann ELISA with high reproducibility but different overall levels.Conclusion: High levels of baseline MRP8/14 are associated with good response to anti-TNF treatment, whereas elevated MRP8/14 levels at discontinuation of etanercept are associated with higher chance to flare.

dx.doi.org/10.1186/s13075-015-0723-1, hdl.handle.net/1765/86014
Arthritis Research & Therapy
This work was funded by the European Commission 7th Framework Programme; grant id fp7/289903 - EUropean TRanslational training for Autoimmunity & Immune manipulation Network (EUTRAIN)
Department of Pediatrics

Anink, J, van Suijlekom-Smit, L.W.A, Otten, M.H, Prince, F.H.M, van Rossum, M.A.J, Dolman, K.M, … Holzinger, D. (2015). MRP8/14 serum levels as a predictor of response to starting and stopping anti-TNF treatment in juvenile idiopathic arthritis. Arthritis Research & Therapy, 17(1). doi:10.1186/s13075-015-0723-1