Screening for chronic kidney disease complications in US adults: racial implications of a single GFR threshold

Abstract

Background and objectives: An ideal and effective screening tool should perform equally across ethnic groups. The objective of this study was to determine whether the widely advocated creatinine-based estimated GFR (eGFR) threshold of 60 ml/min per 1.73 m(2) identifies the typical metabolic abnormalities related to chronic kidney disease equally well in minority and nonminority adults.

Design, setting, participants, & measurements: This objective was addressed using data for 8918 minority and nonminority adult participants in the National Health and Nutrition Examination Survey 2003 through 2006, which used stratified, multistage, probability sampling methods to assemble a nationwide probability sample of the noninstitutionalized population of the United States. Metabolic abnormalities including BP, potassium, hemoglobin, bicarbonate, uric acid, calcium, phosphorus, and parathyroid hormone were defined by fifth or 95th percentile values.

Results: Among participants with eGFR <60 ml/min per 1.73 m(2), black individuals were more likely than white individuals to have low hemoglobin (adjusted odds ratio [aOR] 3.76; 95% confidence interval [CI] 1.94 to 7.28), elevated uric acid (aOR 2.15; 95% CI 1.26 to 3.68), and elevated parathyroid hormone (aOR 3.93; 95% CI 2.33 to 6.66).

Conclusions: Metabolic consequences of reduced eGFR are more common in black individuals and seem to be present at levels well above 60 ml/min per 1.73 m(2); thus, black individuals should be screened for the metabolic complications of chronic kidney at higher GFR levels.

Figure 1.

Fifth, 25th, 50th, 75th, and 95th percentile values for potassium, hemoglobin, uric acid, and parathyroid hormone (PTH) in participants with estimated GFR (eGFR) <60 ml/min per 1.73 m² (dashed lines, top) and in the overall population (solid lines, bottom). ○, white; •, black; ×, Hispanic. Larger symbols denote 50th percentiles. AA, African American; H, Hispanic; W, white.

Figure 2.

In the top two panels, GFR was estimated using the Modification of Diet in Renal Disease (MDRD) Study formula for both white and black participants. In the bottom two panels, GFR was estimated using the MDRD Study formula for white participants and the African American Study of Kidney Disease and Hypertension (AASK) formula for black participants. White individuals are the reference category throughout. Race/ethnicity, age, gender, body mass index, born outside the United States, self-reported diabetes, self-reported hypertension, serum iron, and red blood cell folate were included as adjustment variables in all models; eGFR <60 ml/min per 1.73 m² was used in analysis of the overall population. Variable values: Systolic BP ≥157.7 mmHg, diastolic BP ≥89.7 mmHg, potassium ≥4.5 mmol/L, hemoglobin ≤12.1 g/dl, bicarbonate ≤20.5 mmol/L, uric acid ≥7.7 mg/d L, calcium ≤8.9 mg/dl, phosphorus ≥4.7 mg/dl, PTH ≥81.5 pg/ml.