Urine CD163 Is a Biomarker of Histological Activity in Kidney Biopsies from Pediatric Patients with Lupus Nephritis

Background: Persistent kidney inflammation in patients with lupus nephritis (LN) leads to progressive damage and predisposes to LN flares. Noninvasive monitoring of histologic activity could help optimize LN management. Soluble urine CD163 (uCD163), a scavenger receptor released from tissue macrophages is a marker of inflammation and the histologic activity index (AI) in adult LN patients. We examined whether uCD163 could improve the prediction of AI compared to routine clinical markers in pediatric patients with LN. Methods: In this cross-sectional study, soluble CD163 was measured by ELISA in the urine of 31 pediatric LN patients collected just before kidney biopsy. The ability of uCD163 to predict AI as a single marker or in combination with routinely used clinical markers was assessed. Descriptive statistics, Spearman's nonparametric correlation, binomial logistic regression and area under (AUC) the receiver operating characteristic (ROC) curve analysis were used. Results: We analyzed 31 pediatric patients (Hispanic 65%, female 84%, age 14.8±2.7 years, 68% with proliferative LN). Urine CD163 at a cutoff of 7.59 ng/mg urine creatinine had good predictive performance as single marker to discriminate between an AI of 0 or 1 and an AI>1 (AUC=0.82, Sensitivity=87%, Specificity=77%, 82% of patients correctly classified). The discriminatory capacity of models that included uCD163 was superior to that of each clinical marker evaluated separately, showing good statistical fit and excellent predictive performance (Figure). Conclusion: The novel urine biomarker soluble CD163 has been shown to associate with and predict the kidney histologic AI of adult patients with LN. Here we show that uCD163 is a robust non-invasive biomarker that can be used to discriminate between children with LN who have ongoing or resolved histologic activity. Funding: Private Foundation Support