BNP & NT-proBNP (Heart Failure Test)

What are BNP and NT-proBNP?

B-type natriuretic peptide (BNP) and its inactive fragment NT-proBNP are hormones released by the ventricular walls of the heart when they are stretched or under increased pressure: as happens in heart failure, when the heart cannot pump blood efficiently and fluid backs up. Both tests indicate the same process; different labs use different assays. They are the most important blood tests for: diagnosing heart failure in a patient with shortness of breath, assessing severity, monitoring treatment response, and predicting prognosis.

Normal range and interpretation

Using BNP to monitor heart failure treatment

In a patient already diagnosed with heart failure, serial BNP or NT-proBNP measurements track response to treatment. A falling BNP as medications (ACE inhibitors, ARBs, beta-blockers, diuretics, SGLT2 inhibitors) are optimised indicates improving cardiac function. A rising BNP during apparent stability warns of decompensation before hospitalisation becomes necessary.

Questions to ask your doctor

• Is my shortness of breath from my heart or my lungs?
• What is my BNP trend over time?
• Do I need an echocardiogram?
• How well is my heart failure treatment working?
• What medications protect my heart and reduce my BNP?

Frequently asked questions

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

1. Natriuretic Peptide B Type Test. In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK556136

References

Sources cited on this page. PubMed links open the original abstract.

1. Maisel AS, Krishnaswamy P, Nowak RM, et al. Rapid measurement of B-type natriuretic peptide in the emergency diagnosis of heart failure. N Engl J Med. 2002;347(3):161–167. PMID 12091184 · doi:10.1056/NEJMoa020233

BNP and NT-proBNP – different tests, same diagnostic purpose

BNP (B-type natriuretic peptide) and NT-proBNP (N-terminal pro-BNP) are both derived from the same precursor molecule released when the heart is under pressure or volume overload. When BNP is cleaved from its precursor, NT-proBNP is released as the inactive fragment. Both are used as markers of heart failure, but they are different assays, not interchangeable, and use different reference ranges.

NT-proBNP is more stable in the laboratory and has a longer half-life (60–120 minutes versus 20 minutes for BNP), making it the more commonly used marker. However, NT-proBNP is predominantly cleared by the kidneys – in patients with significant chronic kidney disease (eGFR below 60), NT-proBNP values are substantially higher at baseline, and age-adjusted cut-offs must be used. Most UK laboratories report NT-proBNP. The ESC (European Society of Cardiology) diagnostic threshold for heart failure is NT-proBNP above 125 pg/mL in outpatients, or above 300 pg/mL in acute presentations.

What a normal BNP means – and its high negative predictive value

A normal BNP or NT-proBNP is extremely useful because its primary power lies in ruling out heart failure. In a breathless patient presenting acutely, a BNP below 100 pg/mL (or NT-proBNP below 300 pg/mL) makes heart failure as the cause of breathlessness very unlikely – negative predictive value over 90% in most studies. This makes BNP one of the few biomarkers that can confidently redirect clinical investigation toward other causes (COPD exacerbation, pulmonary embolism, pneumonia, anaemia).

Causes of elevated BNP that are not heart failure

BNP and NT-proBNP are elevated in any condition that increases cardiac wall stress, not just heart failure. Important non-heart-failure causes include: pulmonary embolism (acute right heart pressure overload), cor pulmonale from COPD, atrial fibrillation, sepsis, severe pneumonia, and renal failure (reduced clearance). Age itself raises the normal range. Elevated BNP must always be interpreted in the clinical context – an elevated value in a patient with severe pneumonia and sepsis does not necessarily indicate primary cardiac failure.