Objective: An unsolved problem in juvenile idiopathic arthritis (JIA) is to identify patients at special risk for relapse. It is important to adjust anti-inflammatory and immunosuppressive therapy to the children's actual disease activity especially in times of remission. Our aim was to analyze if the serum levels of MRP8/MRP14 are reliable predictive markers for the risk of relapse in clinically inactive juvenile idiopathic arthritis.
Methods: Serum concentrations of MRP8/MRP14 were determined by ELISA and correlated with laboratory and clinical parameters for disease activity in patients with JIA. 29 patients with changing disease activity were followed up for a mean time of 2.9 years. Two groups of patients--one before relapse (mean 3.7 months) but without clinical signs of disease reactivation, and one in remission for 12 further months--were compared.
Results: MRP8/MRP14 serum levels in patients before relapses were significantly higher than the levels in patients in stable remission for one year (662 ng/ml versus 395 ng/ml; p < 0.05). Using a cut-off for MRP8/MRP14 of 450 ng/ml the likelihood ratio for relapse was 3.7 (positive predictive value 80%), while no differences were found for C-reactive protein and erythrocyte sedimentation rate between the two groups.
Conclusion: MRP8/MRP14 correlate with individual disease activity in patients with JIA. Our data suggest that local disease activity may be present even months before flares become clinically apparent. Serum levels of MRP8/MRP14 can give a hint as to clinically occult disease activity, in this way helping to adjust therapy in times of low disease activity.