Comparative value of BNP and NT-proBNP in diagnosis of heart failure.

UNLABELLED: Heart failure (HF) remains a major diagnostic challenge. Brain natriuretic peptide (BNP) and the N-terminal portion of proBNP (NT-proBNP) have emerged as excellent diagnostic biohumoral indicators in cardiac disease. It is not clear which of the two is superior as a diagnostic marker in HF.

OBJECTIVE: To compare the ability of BNP and NT-proBNP to distinguish subjects with HF from healthy volunteers, as well as to differentiate between HF with left ventricular (LV) systolic dysfunction (SD) and HF with preserved systolic function (PSF).

METHODS: We measured plasma BNP (Shionogi, Osaka) and NT-proBNP (ELECSYS) in 21 healthy individuals (control group [CG]), 11 men, 10 women, mean age 54.4 +/- 11.6 years, with normal ECG and chest X-ray, and in 86 HF patients (HFG), 48 men, 38 women, mean age 71 +/- 11 years, in NYHA II-IV, fulfilling the European Society of Cardiology guidelines: 60 had HF with SD (SDG), ejection fraction (EF) < 40%, and 26 had HF and PSF (PFG), EF > 40%, increased LV mass index and/or dilated left atrium. BNP and NT-proBNP mean and median values were compared and the correlation between the 2 peptides was established. For each peptide sensitivity (sens), specificity (spec) 93.7%, positive predictive value (PPV) 75.5% and negative predictive value (NPV) were calculated. Areas under the ROC curve (AUC) were determined for each group vs. CG and for SDG vs. PFG.

RESULTS: Levels of BNP and NT-proBNP were significantly higher in HF patients, particularly in the SDG, than in healthy subjects. There was reasonable agreement between BNP and NT-proBNP. For BNP, AUC were: HFG vs. CG: 97.7-98.0%; SDG vs. CG: 98.6-99.1%; PFG vs. CG: 95.1-95.9%; PFG vs. SDG: 69.7-70.9%; and for NT-proBNP: HFG vs. CG: 99.2-99.3%; SDG vs. CG: 99.6-99.7%; PFG vs. CG: 98.3-98.5%; PFG vs. SDG: 63.3-63.6%. For a cut-off of 32 pg/ml, BNP has 91.7% sens, 93.7% spec, 75.5% PPV and 98.3% NPV. A NT-proBNP cut-off of 126 pg/ml has 96.3% sens, 98.8% spec, 94.3% PPV and 99.3% NPV.

CONCLUSIONS: Both peptides had an excellent ability to distinguish HF from non-HF subjects. NT-proBNP was more sensitive and specific. Nevertheless, neither peptide could differentiate between the SDG and the PFG by itself. NT-proBNP is a simple, highly effective diagnostic test for HF. A favorable impact on management and costs is expected from implementation of this diagnostic test in clinical practice.