The interrelationships of radioimmunoassayable urinary albumin, renal function and diabetes

Urinary albumin, measured by radioimmunoassay, was evaluated as a method to assess early renal impairment in 76 insulin (IDD) and 36 noninsulin (NIDD)-dependent diabetic patients. Mean albumin excretion in IDD and NIDD patients was significantly higher at 23 and 12 micrograms/100 ml glomerular filtrate (GF) respectively, compared to 4 micrograms/100 ml GF in normal subjects (P less than 0.001 and P less than 0.05). Abnormal albumin excretion from 20 to 200 micrograms/100 ml GF was observed in 30% of IDD patients (P less than 0.001) and 15% of NIDD patients (P less than 0.03). Albumin excretion was significantly increased in hypertensive IDD and NIDD patients. Significant correlations between albumin excretion and age, duration of diabetes and creatinine clearance were observed, but albumin excretion did not correlate with hemoglobin A1C. These data indicate that (1) 30% of IDD patients not clinically recognized as having renal impairment have abnormal albumin excretion, (2) albumin excretion may reflect renal impairment, since albumin excretion levels independently correlate with duration of diabetes and hypertension in both diabetic subgroups and to glomerular function in NIDD patients, and (3) measurement of urinary albumin by radioimmunoassay may be the most sensitive test to evaluate early renal disease in diabetes.