Interleukin-6 is prone to be a candidate biomarker for predicting incomplete and IVIG nonresponsive Kawasaki disease rather than coronary artery aneurysm

Kawasaki disease (KD) is an acute, systemic vasculitis and occurs mainly in childhood. Interleukin-6 (IL-6) is a pleiotropic cytokine synthesized predominantly by neutrophils and monocytes/macrophages and plays an important role in systemic inflammatory disease. However, a little information is currently available on the relationship of serum IL-6 with conventional inflammatory mediators, clinical classification, IVIG response and coronary artery aneurysm (CAA). 165 Chinese children with KD were enrolled and divided into six subgroups, including complete KD, incomplete KD, IVIG-responsive KD, IVIG-nonresponsive KD, coronary artery noninvolvement KD and coronary artery involvement KD. Blood samples were collected from all subjects within 24-h pre- and 48-h post-IVIG therapy, respectively. Serum IL-6 and conventional inflammatory mediators were detected. (1) Serum IL-6 markedly increased in the acute phase of KD, whereas declined to normal after IVIG therapy; it was positively correlated with C-reactive protein and erythrocyte sedimentation rate. (2) Serum IL-6 was significantly elevated in patients with incomplete KD when compared with their complete counterparts. The area under receiver operating characteristic curve (AUC) value for serum IL-6 in prediction of incomplete KD was 0.596, and the estimated sensitivity and specificity were 77.80% and 54.40% with a cutoff of IL-6 > 13.25 pg/ml, respectively. (3) Serum IL-6 was significantly elevated in patients with IVIG-nonresponsive KD when compared with their IVIG-responsive counterparts; the AUC value for serum IL-6 in prediction of IVIG-nonresponsive KD was 0.580, and the estimated sensitivity and specificity were 60.00% and 66.30% with a cutoff of IL-6 > 26.40 pg/ml, respectively. (4) No significant differences in IL-6 were found between KD patients with and without CAA. IL-6 is prone to be a candidate biomarker for predicting incomplete and IVIG nonresponsive KD rather than CAA.