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.

OBJECTIVES: 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).

BACKGROUND: 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.

METHODS: 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.

RESULTS: 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.

CONCLUSIONS: 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.