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 (edema), 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.

A BNP or NT-proBNP test may be ordered under these circumstances:

• In your doctor's office, if you have symptoms that could be due to heart failure.
• In the emergency room, if you are in crisis and doctors need to quickly determine whether you are suffering from heart failure or some other medical problem.
• To monitor the effects of therapy for heart failure.

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.

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. 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.