The conflicting results concerning the prognostic value of NT-proBNP in different COPD cohorts may relate to misclassification of diagnosis or differing prevalence of cardiac complications and comorbidities associated with NT-proBNP and mortality, such as pulmonary hypertension [34], cor pulmonale [35], and left ventricular dysfunction [36–38]. This evidence concerns the gene NPPB and pulmonary arterial hypertension.