NPPB and heart failure: Similarly, a NT-proBNP threshold of 1000 pg/mL achieved our optimal rule-in criteria with a positive predictive value of 74.9% (64.4% to 83.2%) and specificity of 76.1% (65.6% to 84.2%), although performance was also lower within patient subgroups, particularly those without previous heart failure (positive predictive value 62%, 41% to 79%) (supplementary table D; supplementary figure K).