Urinary albumin excretion in the healthy population

In the present study reference values for the albumin excretion rate (AER) and the albumin/creatinine ratio (A/C) in overnight 8-h urine collections (n = 73, group 1) and in 24-h urine collections (n = 25, group 2) were obtained from healthy, nondiabetic, normotensive volunteers. Furthermore, we examined the relationship of these values to age, sex and ethnic group. Albumin was determined by RIA. The mean (+/- SD) values obtained for AER and A/C in overnight urine collections were 6.5 +/- 3.8 mg/24 h and 6.7 +/- 3.6 micrograms/mg creatinine, respectively. These values were significantly lower (P less than 0.001) than the values obtained in 24-h urine collections (AER 11.6 +/- 4.7 mg/24 h and A/C 10.9 +/- 5.0 micrograms/mg creatinine). No difference in AER was observed when the subjects were divided into 10-year age-groups. AER in males was similar to that in females, and AER in European subjects was not different from values obtained for subjects of Oriental (Middle Eastern or North African) origin. Freezing urine specimens resulted in a 25% decrease in AER values. We recommend using freshly obtained 8-h or 24-h urine collections, and considering the excretion of 14 mg/24 h (10 micrograms/min) or 21 mg/24 h (15 micrograms/min), respectively, as the upper limit of normoalbuminuria.