NPPB and chronic thromboembolic pulmonary hypertension: The decision rule identifies the majority of patients with a low risk of CTEPH (i.e., six points or less) who do not need further diagnostic tests.7The rule-out criteria consist of electrocardiography (ECG) reading and N-terminal pro-brain natriuretic peptide (NT-proBNP) measurement with a sex- and age-dependent threshold.8, 9These latter two tests will be applied in patients with a high pre-test probability (more than six points) or clear symptoms suggestive of CTEPH (e.g., persistence of physical impairment or dyspnea).