The relationship between body mass index and N-terminal pro-B-type natriuretic peptide in community-acquired pneumonia

Background: The relationship between body mass index (BMI) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) has not been fully investigated in patients with community-acquired pneumonia (CAP). Methods: This prospective observational study examined 510 consecutive patients hospitalized for CAP. NT-proBNP, BMI, and the pneumonia severity index (PSI) were determined for all participants. The moderating effects of BMI on the relationship between NT-proBNP and CAP mortality were examined using interaction terms in a multivariable regression model. The ability of NT-proBNP to predict mortality was evaluated using the area under the curve (AUC). Results: A significant inverse relationship was observed between BMI and NT-proBNP. After multivariable adjustment including BMI, NT-proBNP remained a significant predictor of CAP mortality. The AUC of the fully adjusted (including BMI) NT-proBNP model was significantly higher than that excluding BMI (p = 0.021) and that of PSI (p = 0.038), respectively. The predictive performance of NT-proBNP for mortality significantly differed by BMI group, with the NT-proBNP of the overweight and obesity group having a significantly higher AUC than that of the underweight and normal-weight group. The AUC of NT-proBNP was significantly higher and tended to be higher than that of PSI in the overweight group (p = 0.013) and the obesity group (p = 0.113), respectively. Conclusions: BMI significantly strengthens the prognostic performance of NT-proBNP in CAP patients. The BMI–NT-proBNP interaction is significantly associated with CAP mortality, but as a prognostic determinant for CAP, NT-proBNP seems to be more useful for overweight and obese patients than for underweight and normal-weight patients.