OBJECTIVETo investigate the clinical significance of serum midkine (MK) in children with henoch-schnlein purpura(HSP).

METHODSOne hundred and six children with HSP admitted in our hospital from March 2013 to March 2016 were enrolled in HSP group, but then 80 healthy volunteers were used as control. MK, interleukin-2 (IL-2), IL-4, IL-6, IL-10, tumor necrosis factor (TNF), interferon γ (IFN-γ) and IL-17 in peripheral blood were measured by ELISA, biochemical indicators including white blood cell count (WBC), platelet (Plt), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), D-dimer, immunoglobulin A (IgA), IgE, IgG, IgM and other clinical data were recorded and analyzed.

RESULTSAmong 106 cases of henoch-schonlein purpura, 42 patients combined with renal failure (isolated hematuria in 4 cases, 17 cases of isolated proteinuria, hematuria and proteinuria in 21 cases). Midkine level in children with HSP was significantly higher than that in the control group [291.70(248.50-396.41) pg/ml vs 217.30(198.98-243.65) pg/ml)](P<0.05); the MK level in group of HSP with nephritis was higher than that in group of HSP without nephritis [326.58(266.58-459.25) pg/ml vs 280.72(233.67-384.36) pg/ml] (P<0.05). IL-4, IL-6, IL-17, TNF and IFN-γ levels in children with HSP were higher than those in the control group(P<0.05), but IL-10 level was lower than that in control group. IL-2 level was not significantly different between 2 groups. Cytokines levels in HSP nephritis group and HSP without renal involvement were not significantly different. Pearson correlation analysis showed that midkine level positively correlated with IL-4, IL-6, IL-17, IgA and IgE (P<0.05). By ROC curve analysis, the AUC of midkine was 0.902, 95% CI 0.841-0.963 (P<0.001), threshold 295.50 pg/ml. The sensitivity and specificity of midkine for predicting Henoch-Schonlein purpura nephritis were 80.60% and 88.30% respecitvely.

CONCLUSIONPlasma MK plays an important role in the development of Henoch-Schonlein purpura and Henoch-Schonlein purpura nephritis. Plasma MK can be used as an effective indicator for early diagnosis and prediction of HSP and renal damage.