Serum levels of immunoglobulin G and complement 3 differentiate non-diabetic renal disease from diabetic nephropathy in patients with type 2 diabetes mellitus.

Abstract

Heavy proteinuria caused by non-diabetic renal disease (NDRD) is common in type 2 diabetes mellitus (T2DM). The aim of this study was to investigate specific predictors for NDRD in addition to traditional indicators in T2DM. A total of 341 patients with T2DM who underwent renal biopsy were retrospectively included. Eligible patients were divided into a nephrotic-range group (n = 194) and a non-nephrotic-range group (n = 147) based on proteinuria level. Risk factors for NDRD were evaluated using logistic regression, and the diagnostic implications of these variables were assessed by subgroup. Multivariate logistic regression indicated that serum IgG level (OR, 0.762; 95% CI, 0.628-0.924; p = 0.006) was an independent predictor of NDRD in the nephrotic-range group. However, in the non-nephrotic-range group, increased C3 level was an independent risk factor for NDRD (OR, 1.313; 95% CI, 1.028-1.678; p = 0.029). In the nephrotic-range group, the optimal cutoff value of IgG for predicting NDRD was 734.0mg/dl, with 67.8% sensitivity and 74.8% specificity, and IgG ≤ 734.0mg/dl was the best predictor of NDRD. In the non-nephrotic-range group, the optimal cutoff value of C3 for predicting NDRD was 122.0mg/dl with low sensitivity (30.9%) but high specificity (97.8%). At different levels of proteinuria, reduced IgG and increased C3 levels were independent indicators of NDRD in T2DM. Insights into these factors will help to advance the clinical management of NDRD.