The Pro B-type natriuretic peptide (Pro BNP) test is a blood test that measures the level of a protein called Pro BNP in the blood. This protein is released by the heart in response to stress or damage to the heart muscle, and its level in the blood can be a useful marker of heart disease. Specifically, Pro BNP is commonly used to diagnose and monitor heart failure, a condition in which the heart is unable to pump blood effectively. A high Pro BNP level can indicate the presence of heart failure, while a low level can help rule out the condition. The Pro BNP test is considered a valuable tool in the diagnosis and management of heart failure, and is often used in combination with other tests and imaging studies.