Importance of Basal Metabolic Index in the Diagnosis of Heart Failure With B-Type Natriuretic Peptide

BACKGROUND: Increased basal metabolic index (BMI) is associated with decreased levels of B-type natriuretic peptide (BNP). This makes the diagnosis of the congestive heart failure challenging in the obese population. We sought to determine the association and strength of the relationship between the two variables. METHODS: The association between BMI and BNP was examined in 405 patients utilizing a retrospective chart review in a single center study. Pearson correlation and regression analyses were performed to identify trends. BNP trends were also correlated with age. RESULTS: The mean age of patients was 77 years with 45% men and 55% women. Mean BNP level was 1,158 standard deviation (SD) ± 1,537. Mean BMI was 33 SD ± 28. BNP levels were found to be inversely related to increasing BMI (P value < 0.001). Using a cut-off of 3,500 pg/mL, there was a linear negative correlation on the dotted graph. In regression analysis the measure of effect of BMI on BNP levels was -0.90 pg/mL. There was no significant association between age and BNP levels (P = 0.90). CONCLUSIONS: Irrespective of age, obese patients have lower BNP levels, complicating the diagnosis of heart failure exacerbation in such patients. Our results suggest that BNP levels in patients with BMI greater than 33 should be adjusted 9 pg/mL per unit increase in BMI.