B-type (brain) natriuretic peptide (BNP) is a hormone produced by cardiac myocytes in response to stretch of the cardiac wall. BNP acts on the kidneys to promote salt wasting (natriuresis) and and renal water loss (diuresis) with a subsequent decrease in the circulating plasma volume. BNP also promotes vasodilation, decreasing peripheral vascular resistance and lowering blood pressure.
Plasma BNP is most commonly used as a screening test for heart failure in a patient with dyspnoea. More specialised uses of BNP include prognostication in patients with established heart failure, and in making clinical management decisions regarding heart failure therapy.
B type natriuretic peptide
Chilled (2 - 8 degrees Celsius)
If overnight - Frozen
In the dyspnoeic patient, BNP results can be interpreted as follows (note that these decision limits apply only to the Beckman Coulter BNP assay currently used at CHL):
|Plasma BNP (pmol/L)||Interpretation|
|<30||Normal. Heart failure is unlikely|
|30-80||Equivocal result. Heart failure is possible. Interpret in the full clinical context|
|>80||Assuming the presence of supportive symptoms and no reason for a falsely high result (see below), this result is supportive of a diagnosis of heart failure.|
There are several other causes of a misleadingly high or low BNP – some of the more common causes are listed below. Of particular relevance are the neprilysin inhibitor drugs (e.g. sacubitril) which cause large elevations in BNP .
|Non-cardiac causes of a low BNP||Non-cardiac causes of a high BNP|
|Drugs – diuretics, ACE inhibitors, vasodilators||Sepsis|
|Drugs – neprilysin inhibitors, nesiritide|
|Endocrine hypertension (e.g. Cushing’s syndrome, hyperaldosteronism)|
Adults: 0 – 29 pmol/L
Two-site immunoenzymatic (“sandwich”) assay performed on Beckman Coulter DxI 800 analysers with Beckman Coulter reagents.
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