NPPB and heart failure: A level of > 400pg/mL suggests that heart failure is potentially a contributor to the patient's symptoms with 90% specificity.(96) For NT-proBNP, a cutoff of 300pg/mL is used to rule out heart failure, whereas optimal 'rule-in' cutoffs vary, depending on age (450pg/mL for < 50 years, 900pg/mL for 50 - 75 years, and 1800pg/mL for > 75 years).(96-98)