OBJECTIVETo study the clinical significance of urinary podocyte marker protein podocalyxin (PCX) in the diagnosis of primary nephrotic syndrome (PNS) in children and the evaluation of disease severity.

METHODSPCX levels in the first morning urine were measured by turbidimetric immunoassay (TIA) in 175 children, including 53 children with acute PNS [36 cases of simple nephrotic syndrome (NS) and 17 cases of nephritic NS], 56 children with PNS in the remission stage (relapsed: 42 cases) and 66 healthy children (control group). Twenty-four hour urinary protein was measured in the 53 children with acute PNS. The optimal operating points for the diagnosis of acute PNS and nephritic NS were determined using the receiver-operating characteristic curve (ROC curve).

RESULTSSignificant increasd levels of urinary PCX were found in children with acute PNS compared with those in the remission stage and the control group (P<0.01). A positive correlation was found between urinary PCX and 24 hour urinary protein in children with acute PNS (r=0.39, P<0.01). In children with acute PNS, urinary PCX levels were significantly higher in the nephritic NS group than in the simple NS group (P<0.05). In children in the remission stage, a significant increase in levels of urinary PCX was found in children who had relapsed compared with those who had not (P<0.05). The area under the ROC curve for the diagnosis of acute PNS and nephritic NS was 0.915 and 0.784 respectively. The optimal operating point for the diagnosis of acute PNS and nephritic NS was 7.97 and 10.28 ng/mL respectively, with a sensitivity and specificity of 81.1% and 93.4% respectively for acute PNS and of 94.1% and 52.8% respectively for nephritic NS.

CONCLUSIONSThe quantitative detection of urinary PCX is useful in the evaluation of podocyte dynamic changes. It is helpful in the diagnosis of acute PNS and in the differentiation of nephritic NS and simple NS.