An enzyme-linked immunosorbent assay for urinary albumin in patients with insulin-dependent diabetes mellitus.

Microalbuminuria is considered to be an early indicator of diabetic nephropathy. In this report, we developed an enzyme-linked immunosorbent assay (ELISA) for the measurement of urinary albumin (UA) and examined UA in 38 patients with insulin-dependent diabetes mellitus (IDDM). The assay range of ELISA for albumin was 5-1,000 ng/ml, and the albumin levels determined by ELISA were well correlated with those by immunoagglutination methods. The UA values of daytime single-void specimens in control subjects, which correlated significantly with UA excretion rates (micrograms/minute) in 24-hour urine, were 10.9 +/- 8.2 micrograms/mg creatinine. In 38 IDDM patients, there were four cases with microalbuminuria and one case with overt nephropathy. Their disease duration was longer than 8 years, and the diabetic control was fair to poor. On SDS-PAGE analysis. the urinary protein of the cases with microalbuminuria consisted mainly of albumin, and in the case of nephropathy, an IgG band was also detected. The measurements of UA in single-void specimens by ELISA is a satisfactory approach to detect impending nephropathy in IDDM patients.