Definition of kidney dysfunction as a cardiovascular risk factor: Use of urinary albumin excretion and estimated glomerular filtration rate

Background: Urinary albumin excretion (UAE) and estimated glomerular filtration rate (eGFR) have been used separately to provide information about cardiovascular risk. We analyzed whether UAE and eGFR used together provide complementary information. Methods: We analyzed UAE, eGFR, cardiovascular risk factors, and incidence of cardiovascular disease in 1665 men and women of the Gubbio Population Study (aged 45-64 years). We designated UAE in the highest decile as high (≥ 18.6 μg/min in men and ≥ 15.7 μg/min in women) and eGFR in the lowest decile as low (<64.20 mL/min/1.73 m² in men and <57.90 mL/min/1.73 m² in women). Results: Kidney dysfunction defined using both markers was more frequent than using 1 marker (UAE alone or eGFR alone) (P <.001) because high UAE and low eGFR clustered in different individuals and were weakly associated with each other (P = .12). The hazard ratio (HR) for incident cardiovascular disease was elevated for both markers, independently of each other (HR for high UAE, 2.15; 95% confidence interval [CI], 1.33-3.49; HR for low eGFR, 2.14; 95% CI, 1.32-3.48). Kidney dysfunction defined by both markers predicted cardiovascular disease independently of sex, age, hypertension, hypercholesterolemia, smoking, diabetes mellitus, prior cardiovascular disease, left ventricular hypertrophy, and obesity (HR, 1.50; 95% CI, 1.05-2.14). The discriminant power of dysfunction defined by both markers was statistically significant (area under the receiver operating characteristic curve, 0.569 [P = .02]) and slightly higher than what was found with 1 marker of diabetes mellitus, prior cardiovascular disease, left ventricular hypertrophy, and obesity. Conclusions: High UAE and low eGFR provide complementary information in defining kidney dysfunction because they cluster in different individuals. Concomitant evaluation of both markers should be considered to adequately assess kidney dysfunction and cardiovascular risk.