Diagnostic significance of urinary transferrin in diabetic nephropathy

We evaluated the diagnostic utility of urinary transferrin (Tf) in patients with diabetic nephropathy by comparing the diagnostic findings with those of clinical stage and renal biopsy specimens. According to the rate of urinary albumin excretion, a total of 60 patients with non-insulin-dependent diabetes mellitus were separated into normoalbuminuria (< 28.8 mg/day), microalbuminuria (28.8 approximately 288 mg/day), and overt proteinuria (> 288 mg/day). They were also divided into 5 groups, D0, DI, DII, DIII and DIV according to the severity of glomerular diffuse lesions using Gellman's criteria. Thirty-eight non-diabetic volunteers were used as controls. Using 24-hour urine specimens, Tf was measured by latex-immuno-turbidimetry. Urinary concentrations of albumin, alpha 1-microglobulin, beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase (NAG) were also evaluated. Urinary Tf was significantly increased in the diabetic patients relative to the non-diabetic controls. The incidence of microtransferrinuria (440 approximately 4,400 micrograms/day) was 33.3% in normoalbuminuria, 63.2% in microalbuminuria, and 18.2% in overt proteinuria. The incidence of overt transferrinuria (> 4,400 micrograms/day) was 0%, 36.8% and 81.8%, respectively. Among the diabetic patients, urinary Tf showed a significant increase with respect to the progress of glomerular diffuse lesions. The glomerular diffuse lesions of 10 normoalbuminuric cases with microtransferrinuria were graded as DI in 8 cases, DII in 1 case, and DIII in 1 case. There was a significant correlation between the urinary excretion of Tf and that of albumin, alpha 1-microglobulin or NAG. The findings indicate that urinary Tf may be useful in detecting diabetic nephropathy at an early stage.