Non-albumin proteinuria as a parameter of tubulointerstitial inflammation in lupus nephritis.

Abstract

Tubulointerstitial inflammation (TI) has prognostic significance in the renal outcomes of lupus nephritis. Here, we aimed to determine whether non-albumin proteinuria is associated with TI severity and with the renal response in lupus nephritis. We included patients with biopsy-confirmed lupus nephritis at a tertiary medical center in Korea from January 2011 to April 2017. Patients in whom the urine protein/creatinine ratio (uPCR) and the urine albumin/creatinine ratio (uACR) were measured simultaneously were included. Laboratory data and renal pathology were reviewed. Non-albumin proteinuria was calculated by subtracting uACR from uPCR. The renal response was assessed by the amount of proteinuria present at 6months after treatment with immunosuppressants. Logistic regression analyses were performed to identify factors associated with TI severity and renal response. Out of 45 patients, 36 (80%) had no-to-mild TI, whereas 9 (20%) had moderate-to-severe TI. Proliferative (class III ± V/IV ± V) and nonproliferative (class II/V) glomerulonephritis (GN) were present in 38 (84.4%) and 7 (15.6%) patients, respectively. In the logistic regression analyses, non-albumin proteinuria (uPCR - uACR) was associated with moderate-to-severe TI (odds ratio [OR] 3.166, 95% confidence interval [95% CI] 1.145-8.757, p = 0.026) and was inversely associated with complete renal response (adjusted OR 0.180, 95% CI 0.045-0.718, p= 0.015). In lupus nephritis, non-albumin proteinuria was associated with TI severity and with poor renal response after immunosuppressive treatment. Thus, the determination of non-albumin proteinuria can provide clinically valuable information on lupus nephritis.