[Early detection of diabetic nephropathy: serum beta 2-microglobulin].

Detection of early diabetic nephropathy is necessary to postpone or even prevent progression of irreversible kidney damage by therapeutic measures. Beta 2-microglobulin (beta 2-MG) as a parameter of the glomerular filtration rate has been measured by immunoassay in the serum of 100 diabetic subjects, 50 insulin-dependent (IDD), and 50 noninsulin-dependent (NIDD) patients. The results are compared with endogeneous creatinine-clearance, serum creatinine concentration, and proteinuria and are related to different stages of diabetic retinopathy (RD). Normal values were obtained from 50 healthy age- and sex-matched subjects. A close correlation was found between beta 2-MG levels and endogeneous creatinine clearance. Thirty-nine diabetics revealed an elevated beta 2-MG (2.5 mg/l or higher), only 16 of whom had increased serum creatinine levels (1.4 mg/dl or higher). Significant differences of beta 2-MG were obtained between each group of patients with different stages of RD. A relevant difference of serum creatinine was found only between patients with normal eye fundus and advanced proliferative retinopathy, respectively. Without RD 26% of the patients revealed elevated beta 2-MG but normal creatinine values demonstrating a "latent nephropathy", just 8% showed an increase of both parameters. Of the diabetics with proliferative retinopathy 40% suffered from impaired kidney function proven by reduced creatinine clearance and by elevation of beta 2-MG and creatinine as well, 15% just revealed an increase of beta 2-MG with normal creatinine levels.(ABSTRACT TRUNCATED AT 250 WORDS)