Diabetes in Urban African-Americans: II. High prevalence of microalbuminuria and nephropathy in African-Americans with diabetes

OBJECTIVE: African-Americans with diabetes have an increased risk of endstage renal disease, but underlying mechanisms are poorly understood. We undertook this study to evaluate prevalence and risk factors for renal disease in an African-American population with diabetes. RESEARCH DESIGN AND METHODS: We measured urine albumin excretion in 578 consecutive patients presenting for the first time to the Grady Memorial Hospital Diabetes Unit in Atlanta, GA. The unit serves an urban population that is predominantly African-American; 85% of patients have non-insulin-dependent diabetes mellitus (NIDDM). Subjects provided 24-h and/or approximately 3-h urine collections for measurement of albumin and creatinine. RESULTS: Correlation of the albumin/creatinine ratio (micrograms/mg) with the 24-h albumin excretion rate was 0.89 (P < 0.001, n = 123). Although the median duration of diabetes was only 1 year, among all subjects, the estimated prevalence of microalbuminuria (30-300 mg albumin/24 h) was 25% and that of nephropathy ( > 300 mg albumin/24 h) was 11%. Among African-Americans with NIDDM (n = 466), the estimated prevalence of microalbuminuria was 24% and that of nephropathy was 12%; prevalence remained high (25 and 5%, respectively) among 219 patients with < 1 year known duration of diabetes. Metabolic control was not associated with disease. However, among all subjects with NIDDM, the odds ratio for nephropathy among subjects with disease duration > 5 years compared with those with disease duration < 1 year was 4.65 (95% confidence interval [CI] 2.24-9.79), and the odds ratio for nephropathy among subjects with hypertension compared with those without hypertension was 2.64 (CI 1.42-4.93). Odds ratios were comparable among African-Americans with NIDDM. Trends were similar but less significant for subjects with microalbuminuria. CONCLUSIONS: Albuminuria can be identified reliably and conveniently by the albumin/creatinine ratio in brief urine collections. In our patients, clinically significant albuminuria occurred in 36% of persons at first presentation. Since increased risk was associated with hypertension and control of hypertension can slow progression of renal disease, screening for albuminuria and treatment of hypertension should be aggressive in urban populations of African-Americans with diabetes.