Nephropathy in siblings of African Americans with overt type 2 diabetic nephropathy

Background: The prevalence of abnormal proteinuria and elevated serum creatinine (sCr) concentrations in diabetic sibs of African Americans (AAs) with overt type 2 diabetic nephropathy (DN) or end-stage renal disease (ESRD) is unknown. Methods: We measured urine albumin-creatinine (UAC) ratio, sCr, and hemoglobin A(1c) (HbA(1c)) in 211 sibs from 66 families (66 unrelated index cases with overt type 2 DN/ESRD, 132 of their diabetic sibs, and 13 of their nondiabetic sibs). Overt DN was defined as a UAC ratio of 1,000 mg/g or greater or ESRD attributed to diabetes. All index cases had at least one diabetic sib screened. Results: Given similar mean ages and body mass indices, nondiabetic sibs had lower UAC ratios and HbA(1c) values compared with diabetic sibs and index cases (Wilcoxon's rank-sum test, all P < 0.006). More than 60% of index cases had at least one diabetic sib with a UAC ratio of 30 or greater and 300 mg/g or less. Nearly 35% of index cases had at least one sib with a UAC ratio greater than 300 mg/g. Nearly 24% of index cases had at least one sib with an elevated sCr level (greater than or equal to1.4 mg/dL [124 mumol/L] in women, greater than or equal to1.6 mg/dL [141 mumol/L] in men). Conclusion: Asymptomatic elevations in urinary albumin excretion and sCr levels are frequently present in diabetic sibs of AA individuals with overt type 2 DN. Diabetic sibs of AA individuals with type 2 DN should be the focus of intensive screening and intervention programs to slow the current epidemic of diabetic ESRD. (C) 2002 by the National Kidney Foundation, Inc.