BNP and NT-proBNP - Understand Your Test and Results

Also Known As

Brain Natriuretic Peptide

proBNP

Natriuretic Peptides

Formal Name

B-type Natriuretic Peptide; N-terminal pro b-type Natriuretic Peptide

This article was last reviewed on

June 12, 2015.

This article waslast modified on July 27, 2018.

At a Glance

Why Get Tested?

To help detect, diagnose, and evaluate the severity of congestive heart failure (CHF)

When To Get Tested?

When you have symptoms of heart failure, such as shortness of breath and fatigue, or when you are being treated for CHF

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

What is being tested?

B-type natriuretic peptide (BNP) and N-terminal pro b-type natriuretic peptide (NT-proBNP) are substances that are produced in the heart and released when the heart is stretched and working hard to pump blood. Tests for BNP and NT-proBNP measure their levels in the blood in order to detect and evaluate heart failure.

BNP was initially called brain natriuretic peptide because it was first found in brain tissue (and to distinguish it from a similar protein made in the atria, or upper chambers, of the heart, termed ANP). BNP is actually produced primarily by the left ventricle of the heart (the heart's main pumping chamber). It is associated with blood volume and pressure and with the work that the heart must do in pumping blood throughout the body. Small amounts of a precursor protein, pro-BNP, are continuously produced by the heart. Pro-BNP is then cleaved by the enzyme called corin to release the active hormone BNP and an inactive fragment, NT-proBNP, into the blood.

When the left ventricle of the heart is stretched, the concentrations of BNP and NT-proBNP produced can increase markedly. This situation indicates that the heart is working harder and having more trouble meeting the body's demands. This may occur with heart failure as well as with other diseases that affect the heart and circulatory system. Heart failure is a somewhat misleading term. It does not mean that the heart has stopped working; it just means that it is not pumping blood as effectively as it should be. The increase in circulating BNP or NT-proBNP will reflect this diminished capacity.

Common Questions

How is it used?

A test for B-type natriuretic peptide (BNP) or N-terminal pro b-type natriuretic peptide (NT-proBNP) is primarily used to help detect, diagnose, and evaluate the severity of heart failure. It can be used, along with other cardiac biomarker tests, to detect heart stress and damage and/or along with lung function tests to distinguish between causes of shortness of breath. Chest X-rays and an ultrasound test called echocardiography may also be performed.

Heart failure can be confused with other conditions, and it may co-exist with them. 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 the treatments are often different and must be started as soon as possible.

Although BNP and NT-proBNP are usually used to recognize heart failure, an increased level in people with acute coronary syndrome (ACS) indicates an increased risk of recurrent events. Thus, a health practitioner may use either BNP or NT-proBNP to evaluate risk of a future cardiac event in someone with ACS.
When is it ordered?
A BNP or NT-proBNP test may be ordered in a doctor's office when a person has signs and symptoms that could be due to heart failure. These may include:

Difficulty breathing, shortness of breath

Fatigue

Swelling in the feet, ankles, legs, abdomen

Testing may be done in the emergency room when someone is in crisis and/or has symptoms that could be due to heart failure and health practitioners need to quickly determine if a person is suffering from heart failure or some other medical problem.

Several BNP or NT-proBNP tests may be done over a period of time when an individual is being treated for heart failure to monitor the effects of therapy.
What does the test result mean?

Higher-than-normal results suggest that a person has some degree of heart failure, and the level of BNP or NT-proBNP in the blood is related to its severity. Higher levels of BNP or NT-proBNP are often associated with a worse outlook (prognosis) for the person.

Normal results indicate that the person's symptoms are likely due to something other than heart failure.
Is there anything else I should know?

BNP and NT-proBNP levels decrease in most people who are taking drug therapies for heart failure, such as angiotensin-converting enzyme (ACE) inhibitors, beta blockers, and diuretics.

Levels of both BNP and NT-proBNP tend to increase with age.

Levels of NT-proBNP and BNP may be increased in persons with kidney disease due to reduced clearance.

While both BNP and NT-proBNP will rise with left ventricle dysfunction and either can be measured for diagnosis or monitoring therapy, they are not interchangeable and the results cannot be directly compared.
How common is heart failure?

According to the National Heart, Lung and Blood Institute, about 5.7 million people in the United States are living with heart failure and the number is growing. People who are most at risk are those over 65 years old, African Americans, people who are overweight, those who have diabetes and people who have had a heart attack. Men are more likely than women to develop heart failure.
How is heart failure treated?

For information on treatment, read the article on Congestive Heart Failure or visit the American Heart Association's web site.

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Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

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