Gender- and Race-specific Determination of Albumin Excretion Rate using Albumin-to-Creatinine Ratio in Single, Untimed Urine Specimens:The Coronary Artery Risk Development in Young Adults Study

Abstract

Although albumin excretion rate is commonly estimated by using albumin/creatinine ratio (A/C), gender and race differences in creatinine excretion may bias this estimate. The authors optimize the use of an untimed (spot) urine specimen among 3,371 Blacks and Whites aged 28–40 years in the Coronary Artery Risk Development in Young Adults Study in 1995–1996. Using three 24-hour collections during the year 5 examination, they determined k = 0.68 × 0.88 in Black men, 0.88 in Black women, 0.68 in White men, and 1.0 in White women to reflect gender and race differences in creatinine excretion. The authors then computed A/C adjusted for race and sex differences in creatinine excretion (A/kC) by using an untimed urine sample in the year 10 examination. A/kC ≥ 25 mg/g (194 cases of microalbuminuria and 26 cases of clinical grade albuminuria) was more common among Blacks (9.1%) than among Whites (4.2%) and among men (8.2%) than among women (5.0%). Use of the unadjusted A/C underestimated the prevalence of microalbuminuria among men by 52% and among Blacks by 26%. Adjustment of A/C permitted more accurate estimation of albumin excretion rate. Men and Blacks have a higher albumin excretion rate than do women and Whites and may thereby have an increased risk of microvascular and macrovascular disease.