An aid in in the diagnosis and assessment of severity of congestive heart failure. Both BNP and NT-proBNP are markers of atrial and ventricular distension due to increased intracardiac pressure. Both markers increase in circulating concentration as the severity of heart failure increases, making them equally good markers of the functional stage of heart failure. NT-proBNP is a larger molecule and has a longer half-life that BNP, so its concentration in serum during heart failure will be considerably higher than that of BNP. NT-proBNP is more stable than BNP, so no special precautions such as keeping the sample on ice prior to analysis is required. Also, NT-proBNP is the appropriate assay for those patients being treated with the drug Entresto. This drug is an inhibitor of the protease that degrades the active hormone BNP and thus prolongs its half-life. Patients receiving this drug should be monitored with the NT-proBNP assay to get an accurate assessment of the severity of their heart failure.