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What is being tested?
his test measures the concentration of BNP or NT-proBNP in the blood. BNP is a hormone that helps to regulate blood volume. NT-proBNP is an inactive fragment produced at the same time as BNP.
Both BNP and NT-proBNP are produced mainly in the heart’s left ventricle (the organ’s main pumping chamber). When the left ventricle is stretched, the concentrations of BNP and NT-proBNP in blood can increase markedly. This situation indicates that the heart is working harder and having more trouble meeting the body's demands. This may occur in heart failure (when your heart is not strong enough to pump enough oxygen-rich blood and nutrients to meet your body's needs), as well as other diseases that affect the heart and circulatory system.
How is it used?
Brain natriuretic peptide (either BNP or NT-proBNP) may be used to help diagnose heart failure and to grade the severity of that heart failure. There are various causes of heart failure. Currently, the condition is diagnosed by the presence of symptoms such as swelling in the legs (oedema), difficulty breathing, shortness of breath, and fatigue, in addition to chest X-rays and an ultrasound test called echocardiography. However, heart failure is still often confused with other conditions. BNP and NT-proBNP levels can help doctors differentiate between heart failure and other problems, such as lung disease. An accurate diagnosis is important because heart failure can be successfully managed with various medical treatments.
When is it requested?
A brain natriuretic peptide test may be ordered under these circumstances:
What does the result mean?
A normal result for either BNP or NT-proBNP would exclude the presence of heart failure with a high degree of confidence, indicating the person's symptoms are due to a different condition.
Higher-than-normal results suggest that a person is in heart failure, and the level of BNP or NT-proBNP in the blood is related to the severity of heart failure. Higher levels of BNP or NT-proBNP also may be associated with a worse outlook (prognosis) for the patient.
Release of BNP or NT-proBNP is a natural response to heart failure. As your heart failure is treated, the levels of BNP or NT-proBNP may decrease.
Is there anything else I should know?
BNP and NT-proBNP levels decrease in most patients who have been taking drug therapies for heart failure, such as ACE inhibitors, beta blockers, and diuretics. It is important to inform your healthcare professional if you are taking these medications, so the test result can be interpreted correctly. Do not stop taking these medications without consulting with your healthcare professional.
Levels of both BNP and NT-proBNP tend to increase with age. Levels of NT-proBNP and BNP are increased in persons with kidney disease.
While both BNP and NT-proBNP will rise with left ventricle dysfunction and either can be measured, they are not interchangeable and the results cannot be directly compared.
Common questions
Heart failure is very common in the elderly and affects about 1.5 to 2% of the Australian population.
For information on treatment, please visit the National Heart Foundation web site.
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