The test for B-type natriuretic peptide (BNP) or N-terminal pro b-type natriuretic peptide (NT-proBNP) is originally used to test, detect and also get to diagnose the severity of heart failure (if any) on the whole. This is all because of the fact that BNP and NT-proBNP are the substances that are produced in the heart and they are known to be released when the heart gets to stretch and is struggling to pump blood into the body. It can also be used with several other cardiac biomarker tests and this can be helpful in detecting the heart stress.