Natriuretic Peptide Tests (BNP, NT-proBNP)

The natriuretic peptide tests, including B-type natriuretic peptide (BNP) and N-terminal pro b-type natriuretic peptide (NT-proBNP), are blood tests used to diagnose and monitor heart failure.

What are BNP and NT-proBNP?

BNP and NT-proBNP are hormones produced by the heart in response to strain or stretching of the heart muscle cells, which can occur with heart failure. BNP is a peptide hormone that is released from the ventricles in response to increased wall stress, while NT-proBNP is a prohormone that is released along with BNP and has a longer half-life.

How are the tests performed?

The BNP and NT-proBNP tests involve taking a blood sample from a vein in the arm. The blood is then sent to a laboratory for analysis, where the levels of BNP or NT-proBNP are measured using an immunoassay.

What do the results mean?

The results of the BNP and NT-proBNP tests can help diagnose heart failure and monitor its severity. Elevated levels of BNP or NT-proBNP in the blood indicate that the heart is under strain, which can occur with heart failure.

• Normal values: Less than 100 pg/mL for BNP and less than 300 pg/mL for NT-proBNP.
• Borderline values: 100-300 pg/mL for BNP and 300-600 pg/mL for NT-proBNP. These values may indicate mild heart failure or other conditions such as pulmonary embolism or acute coronary syndrome.
• Elevated values: Greater than 300 pg/mL for BNP and greater than 600 pg/mL for NT-proBNP. These values are often seen in patients with moderate to severe heart failure.

Clinical applications

The BNP and NT-proBNP tests have several clinical applications, including:

• Diagnosis of heart failure: To help diagnose heart failure in patients presenting with symptoms such as shortness of breath, fatigue, or swelling.
• Risk stratification: To assess the severity of heart failure and predict outcomes such as mortality and hospitalization.
• Monitoring treatment: To monitor the effectiveness of treatments for heart failure, such as medications or devices.

Limitations and potential interferences

The BNP and NT-proBNP tests are not perfect and can be influenced by several factors, including:

• Renal function: Impaired renal function can lead to elevated levels of BNP and NT-proBNP.
• Obesity: Obesity can lead to lower levels of BNP and NT-proBNP.
• Aging: Older adults may have higher levels of BNP and NT-proBNP due to age-related changes in the heart.

It is essential to consider these limitations when interpreting the results of the BNP and NT-proBNP tests and to use them in conjunction with other diagnostic tools, such as echocardiography and clinical evaluation.