A 68-year-old man arrives in the emergency department with acute severe dyspnea. To triage whether acute heart failure is the cause, a B-type natriuretic peptide level is sent. Which result makes acute heart failure least likely as the cause of his dyspnea?

• A BNP 420 pg/mL
• B BNP 180 pg/mL
• C BNP 50 pg/mL ✓
• D NT-proBNP 900 pg/mL

Explanation

In the Breathing Not Properly study, a BNP cut-off of 100 pg/mL was established: values below 100 pg/mL make acute heart failure very unlikely (high negative predictive value), while values above 400 pg/mL strongly support it. Intermediate values such as 180 pg/mL fall in the grey zone where other causes like cor pulmonale must be considered. NT-proBNP uses age-adjusted cut-offs, so 900 pg/mL in a 68-year-old exceeds the diagnostic threshold of 900 for patients over 50 and supports heart failure.

Reference: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 12th ed.

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Written and medically reviewed by the StethoPrep medical team.