Definition of kidney dysfunction as a cardiovascular risk factor
Am Fam Physician. 2009 May 1;79(9):796.
Background: Renal impairment is recognized as a marker for cardiovascular risk. Alterations in urinary albumin excretion (UAE) or glomerular filtration, as measured by glomerular filtration rate (GFR) or estimated GFR (eGFR), have been linked with higher rates of cardiovascular disease. It is unknown whether these two tests provide complementary or overlapping information about cardiovascular risk. Cirillo and colleagues compared two markers (high UAE and low eGFR) with one marker (high UAE alone or low eGFR alone, alternatively) in identifying kidney dysfunction and cardiovascular risk.
The Study: The authors recruited a population cohort of white patients 45 to 64 years of age. UAE was determined by using timed overnight urine specimens. eGFR was calculated using the Modification Diet in Renal Disease Study equation (eGFR = 186 × serum creatinine−1.154 × Age−0.203 [× 0.742 for women]).
Patients were considered to have renal dysfunction if their UAE value was in the highest tertile (18.61 mcg per minute or higher in men, and 15.77 mcg per minute or higher in women), or if their eGFR was in the lowest decile (less than 64.20 mL per minute per 1.73 m2 in men, or 57.90 mL per minute per 1.73 m2 in women). Patients were monitored for hospitalizations or death from cardiovascular causes (i.e., cerebrovascular disease, ischemic heart disease, or peripheral artery disease) for the duration of the study.
Results: The cohort consisted of 1,665 patients who were observed for a mean follow-up period of 10.4 years. UAE and eGFR independently identified renal dysfunction in 167 patients (10 percent), but there was poor correlation between patients identified using either test. Each test by itself detected separate populations of patients with kidney dysfunction. When the tests were used simultaneously, 311 patients (18.7 percent) were identified as having renal dysfunction by having an abnormally high UAE or low eGFR.
Renal dysfunction was associated with a greater risk of previous cardiovascular disease (odds ratio ≥ 2.2) and a greater risk of new cardiovascular disease episodes regardless of cardiovascular history (hazard ratio = 2.15 for high UAE, and 2.14 for low eGFR). This risk was independent of other cardiovascular risk factors, such as hypertension, hyperlipidemia, diabetes, smoking, and obesity.
Conclusion: High UAE and low eGFR can be used to detect renal impairment, but tend to identify different subsets of high-risk patients. The authors conclude that using both tests can identify a greater number of patients at risk of cardiovascular events.
KENNETH T. MOON, MD