[Determinations of microproteinuria in early diabetic nephropathy]

Microalbuminuria, transferrin and IgG were determined in the urine of diabetic patients with normal renal function. Microalbuminuria was assayed by the immunoturbidity method, transferrin by the latex agglutination method and IgG by the ELISA method using biotin labelled IgG.HRP labelled protein G. The correlation between microalbuminuria and urinary transferrin concentrations was high (r = 0.902). However, a low titer of transferrinuria was observed, (25.5%) among the patients with microalbuminuria; a wider distribution of transferrinuria was noted than microalbuminuria. Determination of transferrinuria did not appear to be superior to the determination of microalbuminuria in early diabetic nephropathy. The urinary IgG levels assayed by ELISA using biotin labelled IgG.HRP labelled protein G method were distributed from zero to 5 mg/g Cr in the patients with normoalbuminuria. The reference intervals of the urinary IgG concentration should be settled below 5 mg/g Cr. In the patients with microalbuminuria, the concentration of urinary IgG showed a wide variation and no correlation between concentrations of microalbuminuria and urinary IgG was noted (r = 0.02). Determination of urinary IgG is not useful as an early diagnostic procedure for diabetic nephropathy.