NHANES III: influence of race on GFR thresholds and detection of metabolic abnormalities

Whether the creatinine-based glomerular filtration rate (GFR) thresholds used to define chronic kidney disease (CKD) identify metabolic abnormalities similarly in minority and nonminority populations is unknown. We addressed this question among adult participants in the Third National Health and Nutrition Examination Survey (NHANES III) (n = 15,837). GFR was estimated from serum creatinine values and metabolic abnormalities were defined by 5th or 95th percentile values. After adjustment for age, demographic characteristics, and GFR, black participants were significantly more likely than white participants to have abnormal levels of systolic and diastolic blood pressure, hemoglobin, phosphorus, and uric acid. Hispanic subjects were significantly more likely to have abnormal levels of systolic blood pressure, hemoglobin, bicarbonate, and phosphorus. Among participants with GFR < 60 mL/min per 1.73 m(2), black participants were significantly more likely to have abnormal levels of systolic and diastolic blood pressure, hemoglobin, and uric acid; Hispanic subjects were significantly more likely to have abnormal systolic blood pressure levels. Metabolic abnormalities were more common in minority populations, and low GFR appeared to have a multiplicative effect. Defining CKD using a single GFR threshold may be disadvantageous for minority populations because metabolic abnormalities are present at higher levels of GFR.