Quantitative assessment of urinary protein and enzyme excretion—a diagnostic programme for the detection of renal involvement in type I diabetes mellitus

Abstract

In an effort to establish a reliable programme for the clincial monitoring of renal involvement in patients with type-I diabetes mellitus, we quantified the urinary excretion of immunoglobulin G (IgG), transferrin (Tf), albumin (Alb), α1-microglobulin (α1MG), N-acetyl-β-D-glucosaminidase (NAG), and total protein in 130 dipstick negative children and young adults with type-I diabetes. Eighty-five sex-and age-matched healthy persons served as a control group for the definition of the upper reference limits (95th centiles; μg min^-1 1.73 m²): transferrin 1.4; albumin 16.6; total protein 27.1; NAG: 2.0 mU min^-1 1.73 m². Sex-related differences were detected for IgG (men: 3.8; women: 1.7) and α1MG (men: 6.0; women: 4.0 μg min^-1 1.73 m²). The urinary excretion of IgG, Tf, α1MG, NAG, and total protein was significantly higher in subjects with diabetes when compared to healthy controls (p < 0.01). Furthermore, 20 patients (15%) showed an elevated excretion of tubular markers (α1MG and NAG), and 3 patients (2%) of at least two glomerular markers (Alb and/or Tf and/or IgG). Additionally, 18 individuals (14%) presented a mixed excretion pattern of both tubular and glomerular markers. These data suggest that the quantitation of both glomerular and tubular proteinuria provides a sensitive and cost-effective instrument for the non-invasive screening for renal involvement in patients with diabetes mellitus.

Key Words:

• diabetic nephropathy
• glomerular
• tubular proteinuria
• children
• adults