Characteristics of synovial fluid in patients with juvenile idiopathic arthritis

Abstract

IntroductionSynovial fluid (SF) analysis is an important tool for the diagnosis of patients with juvenile idiopathic arthritis (JIA). Patients and methodsA retrospective analysis was carried out of cytological features of SF samples obtained from patients with JIA during the period 2008–2016. ResultsA total of 102 SF samples from 59 patients were analysed. JIA was more common in females (66%). The most frequent form was persistent oligoarticular JIA (52.5%). The median age at onset was 5 years (IQR 2.4–11.8). SF usually showed an inflammatory pattern (median white blood cells count 11,757/mm3; IQR 4,543–18,800), with a predominance of polymorphonuclear (PMN) cells (61%; IQR 30–75). Eight patients (14%) had white blood cells counts of less than 2000cells/mm3, with predominance of mononuclear cells (80%), whereas 3 patients (5%) had white blood cells counts higher than 50,000cells/mm3, with a predominance of PMN cells (90%). Synovial white blood cells count did not show significant differences among the different forms of JIA. The median synovial white blood cells count in ANA-positive patients was 20% lower than in ANA-negative (9,340 vs. 11,600/mm3; P=.23). The proportion of PMN increased with increasing levels of ESR (P<.001) and/or CRP (P=.03). No significant correlation was found between JADAS-10 and synovial white blood cells count (P=.4). SF obtained from different joints in simultaneous arthrocentesis showed a significant correlation P=.001). ConclusionSF from JIA patients usually had inflammatory characteristics, although 19% of the patients showed white blood cells counts below 2000cells/mm3 or higher than 50,000cells/mm3. SF cell count was non-significantly lower in ANA-positive patients, and the proportion of PMN increased with increasing levels of ESR/CRP.