Gray zone BNP levels in heart failure patients in the emergency department: Results from the Rapid Emergency Department Heart Failure Outpatient Trial (REDHOT) multicenter study

Abstract

The study purpose was to examine "gray zone" B-type natriuretic peptide (BNP) levels (100-500 pg/mL) in terms of associated clinical factors, perceived severity, and outcomes in patients with established congestive heart failure (CHF). Although gray zone BNP levels may have diagnostic ambiguity, the implications of these levels in patients with an established diagnosis of CHF have not been examined. REDHOT was a national prospective study in which 464 patients seen in the emergency department with dyspnea had BNP levels drawn. Entrance criteria included a BNP > 100 pg/mL; however, physicians were blinded to the actual BNP level. Patients were followed up for 90 days. Thirty-three percent had gray zone BNP levels. There was no difference in perceived New York Heart Association class (P = .32) or admission rates (P = .76) between the gray zone and non-gray zone groups; 62% of patients with a gray zone BNP were identified as class III or IV CHF. Despite this perceived severity, the 90-day event rate was lower in the gray zone group (19.2% vs 32.9%, respectively, P = .002). Although patients in the gray zone had more symptoms of concomitant pulmonary disease, multivariate analysis could not demonstrate any variable that worsened the prognosis of patients with a gray zone BNP level. In patients with established CHF, those with gray zone BNP levels have a better prognosis than those with non-gray zone levels despite being perceived by physicians as having New York Heart Association class III or IV CHF.