Urinary IgG is a pure strong indicator of diabetic nephropathy than microalbuminuria in type 2 diabetic patients

Microvascular and macrovascular complications are common in type 2 diabetes mellitus. The presence of a trace amount of albumin in the urine was originally considered a marker of renal microangiopathy but recently this concept has been challenged in several respects and microalbuminuria has been found to be associated with epithelial cell damage associated microvascular and macrovascular complications. Hence, the need to look at alternative predictive parameters. Type 2 diabetic patients with and without microvascular (retinopathy) and macrovascular (cardiovascular) complications as a class representative were selected for this study and screened for urinary excretion of microalbumin (mg/g creatinine, UACR) and IgG (mg/g creatinine, UIgGCR). The eGFR was calculated by MDRD equation and patients were sub-classified according to eGFR 60–74 ml/min/1.73 m² and eGFR ≥75 ml/min/1.73 m². The adjusted odds ratio for UACR increases significantly with secondary complications which further increases with declined eGFR up to 1.39 (95 % CI 1.26–1.53, P < 0.001) and 1.41 (95 % CI 1.27–1.57) when adjusted for total antioxidant capacity of plasma (TAC), the adjusted odds ratio for UACR shows a higher influence on adjustment with other traditional confounders. Whereas the odds for UIgGCR was associated with secondary complications in a selective manner, and significant only in patients shown declined renal function (eGFR 60–74 ml/min/1.73 m²) with and without secondary complications. The adjusted odds for UIgGCR in diabetic patients with microvascular and macrovascular complications was insignificant for normal renal function moreover it was 1.22 (95 % CI 1.12–1.33, P < 0.001) and 1.21 (95 % CI 1.11–1.31, P < 0.001) for declined renal function, which further increases if adjusted for TAC as 1.25 (95 % CI 1.13–1.37, P < 0.001) and 1.24 (95 % CI 1.12–1.36 P < 0.001) respectively. These results suggest that IgG could serve as stronger predictor of protenuria over microalbumin in type 2 diabetic patients and might help to identify individuals at higher risk of diabetic nephropathy.