Relationship between N-terminal pro-B-type natriuretic peptide plasma levels and renal function evaluated with different formulae in older adult subjects admitted because of dyspnea.

BACKGROUND: N-terminal pro-B-type natriuretic peptide (NT-proBNP) plasma levels are associated with congestive heart failure severity, and are an important diagnostic tool for assessing patients with acute dyspnea. Reduced renal function increases NT-proBNP concentrations, and therefore it might be a confounding factor in chronic kidney disease (CKD) patients.

OBJECTIVE: The aim of the present study was to relate NT-proBNP plasma levels to different stages of renal function assessed with different methods in older adult subjects admitted because of dyspnea.

METHODS: NT-proBNP plasma levels (Roche Diagnostic, Mannheim, Germany) were measured in 134 older adult patients (age: 80 ± 6 years) admitted to hospital because of dyspnea. Anthropometrics, anamnesis, and biochemical data were collected. Glomerular filtration rate (GFR) was evaluated with different equations, the 4 variables MDRD equations (GFR(MDRD186), GFR(MDRD175)), Mayo Clinic Quadratic formula (GFR(MAYO)), and the new CKD-EPI formula (GFR(CKD-EPI)). Patients were classified into the five K/DOQI stages of CKD and median NT-proBNP values were calculated evaluating their relationship with GFR.

RESULTS: Median NT-proBNP values were better stratified into the five K/DOQI stages by GFR(MAYO) (stage 1 (n = 10) 1,640 pg/ml vs. stage 2 (n = 61) 2,371 pg/ml vs. stage 3 (n = 42) 3,815 pg/ml vs. stage 4 (n = 18) 6,320 pg/ml vs. stage 5 (n = 3) 7,256 pg/ml, p = 0.017). However, similar results were obtained with the other formulae. NT-proBNP was negatively correlated with GFR as evaluated with all the different formulae (r -0.25 to -0.29; all p < 0.01). Multiple regression analysis confirmed the independent association between LnNT-proBNP and GFR.

CONCLUSION: NT-proBNP plasma levels progressively increase with worsening of renal function, and appear to be related to the five K/DOQI stages of CKD. For this purpose, GFR assessed with the GFR(MAYO) formula appears to better stratify NT-proBNP in older adult subjects. Renal function should be considered when interpreting NT-proBNP levels in older adult patients admitted for dyspnoea.