Platelet Indexes and Disease Activity in Juvenile Idiopathic Arthritis

Objective: To test correlation between mean platelet volume (MPV), immature platelet fraction (IPF) with disease activity in a group of juvenile idiopathic arthritis (JIA) patients defined by JADAS 71. Determinate sensitivity, specificity, positive and negative predictive value. Methods: A cross-sectional study included JIA patients with oligoarticular and polyarticular rheumatoid factor negative subtypes, with disease defined activity by JADAS 71. Other subtypes and patients with acute infection, neoplastic diseases, macrophage activation syndrome, other thrombocytopenias, other inflammatory diseases, and use of antiplatelet and anticoagulant medications were excluded. All blood parameters were processed in a SYSMEX XN 1000 haematology analyser. Results: Twenty-five active and 21 inactive JIA disease patients were included. Oligoarticular subtype were 76%, 73,9% were female sex and 95,6% were caucasian. The median age was 10,30 [4,77 – 14] years and the median disease duration was 57 months [ 24 – 90,7]. The median JADAS 71 was 1,35 [ 0 – 10,25] with active disease above 1. There was no correlation between MPV and JADAS 71(rho = 0,204 e p = 0,185). There was no correlation between IPF and JADAS 71 (rho = 0,192 e p = 207). Sensitivity was 13% and specificity was 4,80%. Positive predictive value (PPV) was 75% and negative predictive value (PNV) was 50%. Sensitivity was 4,22%, and specificity was 0,0%, PPV was 36,8% and PNV was 100%. Conclusions: MPV and IPF had no correlation with JADAS 71 in a group of JIA patients Keywords : Juvenile idiopathic arthritis, mean platelet volume, immature platelet fraction, JADAS-71