Assays Specific for BNP1-32 and NT-proBNP Exhibit a Similar Performance to Two Widely Used Assays in the Diagnosis of Heart Failure

BACKGROUND: Secretion of cardioprotective B-type natriuretic peptide 1-32 (BNP1-32) is increased proportionately with cardiac dysfunction, but its measurement in plasma is difficult. Therefore, less specific BNP and amino-terminal proBNP (NT-proBNP) assays that detect the precursor molecule proBNP alongside BNP or NT-proBNP metabolites were developed to reflect BNP1-32 secretion and are now mandated in the diagnosis of heart failure (HF). We compared the diagnostic performance of 2 widely used clinical assays: the Roche proBNPII assay, and Abbott BNP assay, against our recently developed in-house assays that measure either intact BNP1-32 or NT-proBNP. METHODS: EDTA plasma samples obtained from patients presenting with breathlessness (n = 195, 60 [31%] with clinically adjudicated HF) were assayed using the Roche NT-proBNP and our specific in-house BNP1-32 and NTBNP assays. A subset (n = 75) were also assessed with the Abbott BNP assay. RESULTS: Roche NT-proBNP was highly correlated with BNP1-32 and NTBNP (Spearman rho = 0.92 and 0.90, respectively, both Ps < 0.001), and all 3 assays similarly discriminated acute HF from other causes of breathlessness (ROC analysis areas under the curve 0.85-0.89). The Abbott BNP assay performed similarly to the other assays. Roche NT-proBNP and BNP1-32 assays had similar sensitivity (83% and 80%), specificity (83% and 84%), positive (70% and 71%) and negative (91% and 90%) predictive values, and accuracy (both 83%) at their optimal cutoffs of 1536 and 12 ng/L, respectively. CONCLUSIONS: Since all assays exhibited similar performance in the diagnosis of HF, currently mandated assays provide a reliable proxy for circulating concentrations of active BNP1-32 in HF diagnosis.