Role of Serum MRP8/14 in Predicting Response to Methotrexate in Children With Juvenile Idiopathic Arthritis

Objective Nearly 40% of children with juvenile idiopathic arthritis (JIA) might not respond to first-line disease-modifying antirheumatic drugs (DMARDs) including methotrexate (MTX). Hence, there is a need for a biomarker that can predict MTX response and help in tailoring initial therapy. Our objective was to study the role of serum myeloid-related protein (MRP) 8/14, and other inflammatory cytokines, as predictors of response to MTX among children with JIA. Methods We did a longitudinal follow-up study among children diagnosed with JIA at our institute. All MTX-naive children with JIA requiring DMARDs were eligible for this study; those who either took corticosteroids or DMARDs for more than 6 weeks at time of presentation were excluded. The demographic and clinical information was collected using a pretested semistructured questionnaire, and selected biomarkers were collected at baseline and again at 3 months. Response at 3 months was assessed using the American College of Rheumatology (ACR) criteria; responders were children who achieved ACR50, whereas those failing to achieve ACR30 were classified as nonresponders. Multivariate binary logistic regression was done to assess determinants of being a responder. Results We enrolled 69 children (36 boys) with JIA, of which 48 (69.5%) were responders. The baseline value of serum MRP8/14 was significantly higher in responders (median, 144.34 [interquartile range, 88.54-188.34] ng/mL) compared with the nonresponders (median, 95.34 [interquartile range, 76.54-130.28] ng/mL), p = 0.047. Being a responder was significantly associated with baseline serum MRP8/14 with adjusted odds ratio of 1.01 (95% confidence interval, 1.00-1.02). Conclusions The baseline levels of MRP8/14 were significantly raised in children meeting ACR50 at follow-up and suggest a prognostic value in predicting response to MTX.