Biomarker · Heart

Natriuretic peptides (BNP and NT-proBNP)

Also known as: BNP, NT-proBNP, B-type natriuretic peptide, brain natriuretic peptide

Hormones released by the heart's ventricles when their walls are stretched by high pressure or volume. A normal level makes heart failure unlikely; a high level in someone breathless calls for an echocardiogram and specialist assessment.

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Also known as
BNP, NT-proBNP, B-type natriuretic peptide, brain natriuretic peptide
Units
ng/L (pg/mL) for both peptides; BNP and NT-proBNP have separate thresholds and are not interchangeable
Measured by
BNP and NT-proBNP test, Echocardiogram, Electrocardiogram

What it is and what it does

Ventricular muscle cells make pro-BNP and split it into active BNP and the inactive fragment NT-proBNP; laboratories measure one or the other, and the two have different reference limits. BNP acts on the kidney to shed sodium and water and relaxes blood vessels, a natural counterweight to the fluid retention of heart failure. Because release is proportional to wall stress, the level rises with heart failure of either reduced or preserved ejection fraction, with valve disease, atrial fibrillation and pulmonary embolism. Guidelines use NT-proBNP bands to decide how urgently a person with suspected heart failure should be seen for echocardiography.

Why it may be higher

  • Heart failure of any cause, valve disease, myocardial infarction
  • Atrial fibrillation, pulmonary embolism, pulmonary hypertension
  • Chronic kidney disease (reduced clearance), sepsis, older age
  • Left ventricular hypertrophy, some chemotherapy

Why it may be lower

  • Obesity lowers the level, which can mask heart failure
  • Treatment with diuretics, ACE inhibitors, ARBs and sacubitril/valsartan changes levels (sacubitril raises BNP but not NT-proBNP)

A high or low value can be associated with several different situations. The result is interpreted with other results, symptoms, history and clinical findings.

What can affect the result

  • Age, kidney function and body weight
  • Whether the laboratory measures BNP or NT-proBNP
  • Acute illness on the day of sampling
Reference ranges. Reference intervals for this marker depend on the laboratory, the assay, the units, age, sex and pregnancy. Interpret a result against the interval printed on the laboratory report, not against a figure from the internet.
Educational content. A biomarker page explains what a substance is and why its level can change. It cannot determine the cause of your result: interpret a result using the range supplied by the laboratory that performed the test, with the clinician who ordered it.