Changes and significance of serum midkine in children with allergic purpura and purpura nephritis

Abstract

Objective To investigate the role of midkine(MK)in the pathogenesis of Henoch-Schonlein purpura(HSP) and Henoch-Schonlein purpura nephritis(HSPN). Methods In the case group, 35 cases were hospitalized in the pediatric kidney rheumatism immunology ward of Shengjing hospital affiliated to China Medical University from December 2016 to January 2018.Among them, 10 cases were HSP, 25 were HSPN.According to quantitative level of 24-hour urine protein, HSPN group was divided into HSPN(nephrotic level of proteinuria)group of 15 cases and HSPN(non-nephrotic level of proteinuria)group of 10 cases.The control group consisted of 12 healthy cases who underwent physical examination at outpatient department in the same period in the developmental pediatric clinic of our hospital.Blood samples were collected to detect MK.The other clinical datas including renal function, 24-hour urine protein quantitative, immunoglobulin, etc were collected.The serum MK and renal function indexes were compared among groups.The correlation between MK and various clinical indicators was analyzed, and the receiver operating characteristic(ROC) curve was used to analyze the diagnostic significance of MK for HSP and HSPN. Results MK level of case group was higher than that of healthy control group[(289.34±160.70)pg/ml vs.(100.03±56.75)pg/ml, P<0.05]. Moreover, the difference of MK concentration among the HSPN(nephrotic proteinuria)group, the HSPN(non-nephrotic proteinuria)group and the HSP group was still statistically significant[(449.91±141.91)pg/ml vs.(244.04±89.15)pg/ml vs.(175.94±46.30)pg/ml, P<0.05]. MK was positively correlated with urine microalbumin(r=0.54), IgA(r=0.132), IgE(r=0.304), urine β2 microglobulin(r=0.483), 24-hour urine protein /body weight(r=0.503), and urine transferrin level(r=0.509)in the case group(P<0.05). According to the ROC curve, the area under ROC of MK for predicting the diagnosis of HSP was 0.908(95%CI 0.828-0.988). The optimal value in predicting the diagnosis of HSP was 182.762 pg/ml, with sensitivity and specificity of 81.4% and 91.7%.The area under ROC of MK in predicting HSPN was 0.947(95%CI 0.888-1.000), and the optimal value of predicting HSPN was 218.186 pg/ml, with sensitivity and specificity of 84.0% and 95.5%. Conclusion MK may be involved in the pathogenesis of HSP and HSPN.It can provide the basis for clinical diagnosis of HSP and HSPN, and has significance in evaluating the degree of renal damage of HSPN. Key words: Henoch-Schonlein purpura; Henoch-Schonlein purpura nephritis; Midkine; Children