Utility of untimed urinary albumin measurements in assessing albuminuria in black NIDDM subjects

OBJECTIVE - To determine the usefulness of an untimed morning urine specimen in screening a black NIDDM population attending an urban diabetes clinic for microalbuminuria. RESEARCH DESIGN AND METHODS - Untimed morning specimens were provided by 218 black NIDDM subjects. Of the 218 subjects, 123 also provided 24-h urine specimens. The 24-h specimens were assayed for albumin excretion rate (AER) in milligrams per 24 h, and the albumin-to-creatinine ratio (A-to-C) in micrograms per milligram was determined on the untimed morning urine specimen. RESULTS - Correlation between the A-to-C ratio and the 24-h AER was 0.96 (P = 0.0001). In the range of clinical proteinuria, r was 0.92 (P = 0.003, n = 7). In the range of microalbuminuria, r was 0.55 (P = 0.005, n = 26), and in the normal range, r was 0.59 (P less than or equal to 0.0001, n = 90). Analysis of the untimed urine specimens from 218 black NIDDM subjects showed that 171 had A-to-C <30 mu g/mg, 38 had A-to-C 30-300 mu g/mg, and 9 had A-to-C >300 mu g/mg. Data were grouped according to duration of NIDDM and the presence or absence of hypertension. None of the newly diagnosed NIDDM patients (<1 year) (n = 40) had microalbuminuria. The frequency of microalbuminuria and clinical proteinuria increased with 1) duration of NIDDM 5-10 years (odds ratio [OR], 3.39; 95% CI 1.17-9.82), 2) duration of NIDDM >10 years (OR, 11.03; 95% CI 4.16-29.25), and 3) presence of hypertension (OR, 2.59; 95% CI 1.20-5.61). CONCLUSIONS - The A-to-C ratio obtained from an untimed morning urine specimen correlates with the AER from a 24-h collection. In black subjects with newly diagnosed NIDDM, microalbuminuria is not present to a significant degree. Duration of NIDDM >5 years is associated with increased prevalence of microalbuminuria, and hypertension is associated with microalbuminuria and clinical proteinuria in this population.