BNP and NT-proBNP test
Also known as: natriuretic peptide test, B-type natriuretic peptide, heart failure blood test
A blood test for the natriuretic peptides the heart's ventricles release when they are stretched by high pressure or extra volume. It is the first test for suspected heart failure: a normal level makes heart failure unlikely, while a raised level in a breathless person calls for an echocardiogram and specialist assessment within a set time.
- Canonical name
- B-type natriuretic peptide
- Abbreviations
- BNP, NT-proBNP
- Kind
- Laboratory test
- Categories
- Cardiovascular, Chemistry & metabolic
- Specimen
- Serum or plasma
- Method
- Immunoassay
- Terminology
- LOINC 30934-4, 33762-6
- Type
- Blood test
- Sample
- Blood from a vein
- Used for
- Suspected heart failure, monitoring heart failure
- Measures
- BNP or NT-proBNP released by stretched ventricles
- Result
- Numeric, read against guideline referral thresholds
Why is it used?
- Breathlessness, ankle swelling or fatigue where heart failure is possible
- Deciding how urgently a person needs echocardiography
- Prognosis and monitoring of known heart failure
- Assessing the heart in pulmonary embolism and sepsis
What does it measure?
| Component | What it measures | A higher value may be seen in | A lower value may be seen in |
|---|---|---|---|
| Natriuretic peptides (BNP and NT-proBNP) NT-proBNP NT-proBNP or BNP | Natriuretic peptide concentration | Heart failure, valve disease, atrial fibrillation, pulmonary embolism, kidney disease, older age | Obesity can lower the level; a low level makes heart failure unlikely |
A high or low value can be associated with several different situations; the result is interpreted with other results, symptoms, history and clinical findings.
How is it performed?
A venous blood sample; no special timing.
Specimen. Venous blood (plasma or serum)
Do I need to prepare?
None.
What do the results generally mean?
| Finding | What it may indicate |
|---|---|
| NT-proBNP below 400 ng/L (or BNP below 100 ng/L) in an untreated person | Heart failure is unlikely; another cause of the symptoms is looked for |
| NT-proBNP 400-2000 ng/L | Heart failure possible: referral for echocardiography and specialist assessment within six weeks in UK guidance |
| NT-proBNP above 2000 ng/L | High likelihood and worse prognosis: urgent referral within two weeks |
| Raised level with obesity or on heart-failure treatment | Obesity lowers natriuretic peptides and treatment changes them, so results are read with these in mind |
Guideline thresholds
| Threshold | Value | Unit | Applies to | Country · source |
|---|---|---|---|---|
| Heart failure unlikely | below 400 | ng/L NT-proBNP | Suspected heart failure in an untreated person; consider other causes of symptoms | UK UK |
| Refer within 6 weeks | 400 to 2000 | ng/L NT-proBNP | Specialist assessment and echocardiography within 6 weeks | UK UK |
| Urgent referral within 2 weeks | above 2000 | ng/L NT-proBNP | Specialist assessment and echocardiography within 2 weeks | UK UK |
Clinical decision thresholds come from the named guideline and country; they are not laboratory reference intervals, and they change when guidance changes.
What can affect the result?
- Obesity (lower), older age and female sex (higher)
- Kidney function
- Atrial fibrillation, pulmonary embolism, sepsis, lung disease
- Heart-failure medicines, including diuretics and sacubitril/valsartan, which raises BNP but not NT-proBNP
Medicines. Sacubitril/valsartan raises BNP (which it stops being broken down) but not NT-proBNP; diuretics and other heart-failure treatment lower both.
What can the test not tell you?
- Whether the heart's pumping is reduced or preserved
- Which valve or chamber is affected
- Whether breathlessness has a lung rather than a heart cause
Natriuretic peptides show that the heart is under strain, not why: kidney disease, older age, atrial fibrillation, pulmonary embolism and sepsis all raise them, and obesity can lower them enough to mask heart failure. The test cannot describe the structure or pumping function of the heart; that is the echocardiogram's job.