What is a BNP test?

A BNP test is a blood test that checks the levels of a chemical compound associated with heart failure. In individuals with healthy hearts, B-type natriuretic peptide (BNP) in the blood is generally low. Levels begin to rise when the heart begins to fail, and the higher the levels, the more severe the heart failure. This diagnostic screening test may be ordered in an emergency room as part of an incoming patient evaluation and may also be recommended by a physician concerned that a patient may be suffering from heart failure.

B-type natriuretic peptide, also known as brain natriuretic peptide, is produced in the ventricles of the heart. The harder the heart has to work, the more BNP the ventricles produce. As heart failure progresses, the heart works harder and harder to circulate blood effectively, leading to an increase in this compound. Since it circulates through the blood, a simple blood draw can be used for a BNP test, making it a minimally invasive diagnostic test and also very affordable.

Certain things can cause BNP to rise when a patient does not have heart failure. These include some drug therapies, age, and kidney disease. These factors must be taken into account when evaluating the results to determine how to move forward. An important function of the BNP test is to rule out some possible diagnoses, such as lung disease, for a patient's symptoms. If the test is positive and a doctor thinks heart failure is a likely diagnosis, a screening test, such as echocardiography, may be used to find out what's going on inside the patient.

For the test, a small blood sample will be needed. Additional vials may be taken to provide a complete evaluation, depending on what the doctor has ordered. The test does not take long, with results typically available very quickly at a hospital or clinic that has a full-service laboratory. For non-emergency cases, a doctor may ask a patient to fast before taking the BNP test to get more meaningful results, on a case-by-case basis.

It's important to remember that having a high BNP does not automatically mean heart failure. Levels may be elevated for other reasons or the test may not have been performed correctly. High levels imply the need for more follow-up and additional diagnostic tests. Patients can discuss the findings of the BNP test with their physicians to determine what action would be appropriate in their case.

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