NT-proBNP is a 76–amino acid N-terminal fragment that is generated when proBNP is proteolytically cleaved into BNP (biologically active) and NT-proBNP (not biologically active). Both BNP and NT-proBNP are released in response to changes in pressure inside the heart, which can be related to heart failure and other cardiac problems. Like BNP, NT-proBNP is useful in the diagnosis and prognosis of heart failure and is considered a gold standard biomarker in heart failure. Levels of NT-proBNP can be measure quantitively using a two-site sandwich ELISA or CLIA assay.