Assay of urinary protein carbonyl content can predict the steroid dependence and resistance in children with idiopathic nephrotic syndrome

Abstract

Nephrotic syndrome in pediatric age is mostly idiopathic. Idiopathic nephrotic syndrome (INS) by default is treated with steroids from the very beginning. Some do not respond to steroids and are grouped later as either steroid-resistant (SR) or steroid-dependent (SD) cases. The protein selectivity index often fails to predict the SR and SD cases. The SD and SR cases of INS exhibit higher degrees of oxidative stress compared to steroid responders. Proteins get carbonylated when they are exposed to free radicals. The significance of excretion of these carbonylated proteins in urine is yet to be studied in detail. In this study, 70 cases of INS were enrolled, and urinary protein carbonyl content (UPCC) was estimated by Levine’s method before starting the steroid therapy. All the cases were followed up and, based on the response to steroid therapy, were grouped as Group A (n = 47). Steroid sensitive and Group B (n = 23), SD + SR cases. UPCC was significantly higher in Group B compared to Group A. Receiver–operating curve showed at a cutoff limit of 5.10 nmoles/mg of protein, UPCC can predict SD or SR cases with 83.3% sensitivity and 85.2% specificity and area under the curve of 0.833, P<0.05. UPCC levels more than 5.10 nmoles/mg of protein, before starting the therapy can predict SD or SR in pediatric INS cases.