Elevation of serum IgA is of little diagnostic utility in patients with type 2 diabetes mellitus and nephropathy

Serum IgA levels in patients with diabetic nephropathy and IgA nephropathy superimposed on diabetes mellitus

The aim of this study was to examine the relationship between serum immunoglobulin A (IgA) levels and diabetic nephropathy in patients with type 2 diabetes mellitus, and to describe the role of IgA nephropathy superimposed on diabetes mellitus. A total of 127 type 2 diabetic patients were studied. Of these diabetics, 74 had no proteinuria, 35 had diabetic glomerulosclerosis confirmed by renal biopsy, 13 had superimposed IgA nephropathy, and five had superimposed non-IgA nephropathy. We also studied 93 non-diabetic patients with IgA nephropathy, 24 non-diabetic patients with non-IgA nephropathy, and 38 non-diabetic controls. Serum IgA levels were significantly higher in IgA nephropathy patients (350+/-130 mg/dl) than in non-diabetic controls (228+/-56 mg/dl) and diabetics without proteinuria (268+/-104 mg/dl). Serum IgA levels were also significantly higher in diabetics with superimposed IgA nephropathy (470+/-208 mg/dl) than in non-diabetic controls, non-IgA nephropathy patients (270+/-133 mg/dl), diabetics without proteinuria, diabetic glomerulosclerosis alone (302+/-126 mg/dl), and diabetics with superimposed non-IgA nephropathy (248+/-137 mg/dl). The prevalence of high serum IgA levels was significantly higher in diabetics with superimposed IgA nephropathy (76.9%) than in diabetic glomerulosclerosis alone (31.4%) and diabetics with superimposed non-IgA nephropathy (25.0%). In conclusion, our findings indicate that high serum IgA level is a sign of the existence of IgA nephropathy superimposed on diabetes mellitus.