Beta 2-microglobulinaemia: a sensitive index of diminishing renal function in diabetics.

A sensitive single measure of diminishing renal function is of importance in attempts to modify the progression of diabetic nephropathy. In 12 insulin-dependent diabetics with proteinuria plasma concentrations of beta 2-microglobulin were found to correlate more closely than plasma creatinine concentrations or creatinine clearance with glomerular function as measured by clearance of 52Cr-EDTA. The plasma beta 2-microglobulin concentration was raised in all patients with diminished glomerular filtration rate (below 80 ml/min/1.73 m2). By contrast, in two of these patients plasma creatinine concentration was normal. Plasma beta 2-microglobulin concentrations were stable throughout the day and not affected by food intake, unlike plasma creatinine concentrations, which rose in the afternoon and evening and after a meat meal. Plasma beta 2-microglobulin concentrations were the same in venous and capillary blood, the capillary blood being readily self-collected. Concentrations of beta 2-microglobulin were stable for up to 24 hours when whole blood was stored at 4 degrees C; adding aprotinin inhibited loss of beta 2-microglobulin for up to seven days. The results of this study suggest, therefore, that measuring beta 2-microglobulin concentrations is a simple and accurate method of detecting minor degrees of renal impairment and monitoring the effects of treatment.