Measurement of urinary albumin excretion rate (AER) in normal and diabetic subjects

The chemico-clinical characteristics of two commercial RIA kits for the measurement of urinary albumin excretion in normal and diabetic subjects were compared. The chief difference between the two methods concerns the bound/free separation of the antigen, since one employs the second antybody plus PEG (Sclavo Kit), while the other uses the solid phase [antiserum bound to sepharose (Pharmacia kit)]. The two RIA methods have demonstrated a similar degree of sensitivity, feasibility and cost. The precision of the two RIAs was also similar, although the Sclavo kit has shown a better precision for lower albumin concentrations and the Pharmacia kit for higher values. In diabetic patients, elevated urinary albumin concentrations (>60 mg/L) have been found more frequently than low values (<5 mg/L); hence the Pharmacia kit seems to be preferable, because it less frequently needs dilution of urinary sample for measuring with a better precision supranormal urinary albumin values. A significant bias (about 15%) was found between the two RIAs. Bias between different albumin RIA methods could partially explain the differences of normal values previously reported in the literature