Racial Differences in NT-proBNP
Do racial differences in natriuretic peptide levels contribute to racial disparities in clinical outcomes, particularly all-cause and cause-specific mortality?
The final study cohort was comprised of 1,998 individuals from the REGARDS (Reasons for Geographic and Racial Differences in Stroke) study after exclusions (including patients with prevalent cardiovascular disease [CVD] and renal dysfunction) in whom baseline N-terminal pro–B-type natriuretic peptide (NT-proBNP) levels were measured. The REGARDS study is a national population-based cohort study evaluating racial and geographic disparities in stroke in US adults ≥45 years of age. The study authors estimated racial differences in NT-proBNP and they meta-analyzed the percentage difference in NT-proBNP levels by race. They compared these data with published results from the Dallas Heart Study and the Atherosclerosis Risk in Communities Study. They evaluated the association of racial differences in NT-proBNP levels with all-cause and cause-specific mortality. They defined CV mortality was as death from any of the following adjudicated events: myocardial infarction, stroke, sudden death, heart failure, pulmonary embolism, noncardiac CVD, and other cardiac causes of death. They considered any other deaths as non-CV deaths.
In the study cohort, 48.6% (n = 972) were women, 34.7% (n = 694) were obese, 49.1% were black, and median age was 63 years (interquartile range [IQR], 54-72 years). The median NT-proBNP level was 53 pg/ml (IQR, 28-97 pg/ml); median NT-proBNP levels in black individuals were significantly lower than those in white individuals (46 pg/ml [IQR, 23-91] vs. 60 pg/ml IQR, 33-106]; p < 0.001). After multivariable adjustment, NT-proBNP levels were up to 27% lower in black individuals as compared with white individuals (β, –0.32; 95% confidence interval [CI], -0.40 to -0.24; p < 0.001) in the REGARDS study. In a meta-analysis of the three cohorts, NT-proBNP levels were 35% (-42.31 to -26.66; I2 = 86%; p < 0.001) lower in black individuals than white individuals. They also found that among the REGARDS study participants, for every 1-standard deviation higher log NT-proBNP, there was a 31% increased risk of mortality in the multivariable-adjusted model (hazard ratio, 1.31; 95% CI, 1.11-1.54). This increase was driven primarily by association of NT-proBNP with CV mortality (hazard ratio, 1.69; 95% CI, 1.19-2.41; p = 0.004). They found no interaction between race and NT-proBNP levels with all-cause or cause-specific mortality (likelihood ratio [LR] χ2 = 0.30; p = 0.96), CV mortality (LR χ2 = 3.23; p = 0.36), and non-CV mortality (LR χ2 = 1.78; p = 0.62).
The authors concluded that plasma NT-proBNP levels were significantly lower in black males.
NT-proBNP is predominantly excreted by the kidneys. Given that estimated glomerular filtration rate (eGFR) is higher in blacks raises the question of whether this is a reason for lower NT-proBNP levels in blacks. The findings of this study suggest that new NT-proBNP cutoff thresholds need to be developed for blacks (or ‘corrected’ for eGFR)—this is important to apply NT-proBNP more accurately in the African-American heart failure population. Like other risk markers, NT-proBNP levels are probably a continuum in assessing increased risk in all heart failure patients. More prospective studies are required to determine the value of NT-proBNP as a predictor of CVD, particularly in the African-American population.
Keywords: African Americans, Atherosclerosis, Biological Markers, Death, Sudden, Glomerular Filtration Rate, Heart Failure, Myocardial Infarction, Natriuretic Peptide, Brain, Peptide Fragments, Pulmonary Embolism, Risk Assessment, Secondary Prevention, Stroke
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