Does N-Terminal Pro–B-Type Natriuretic Peptide Improve the Risk Stratification of Emergency Department Patients With Syncope?

Abstract

Studies have reported that natriuretic peptides provide prognostic information for emergency department (ED) syncope. To evaluate whether adding N-terminal pro–B-type natriuretic peptide (NT-proBNP) to the Canadian Syncope Risk Score (CSRS) improves prediction of 30-day serious adverse events (SAEs). Prospective cohort study. 6 EDs in 2 Canadian provinces. 1452 adult ED patients with syncope. Serum NT-proBNP was measured locally at 1 site and batch processed at a central laboratory from other sites. The concentrations were not available to treating physicians or for adjudication of outcomes. An adjudicated composite outcome of 30-day SAEs, including death and cardiac (arrhythmic and nonarrhythmic) and noncardiac events. Of 1452 patients enrolled, 152 (10.5% [95% CI, 9.0% to 12.1%]) had 30-day SAEs, 57 (3.9%) of which were identified after the index ED disposition. Serum NT-proBNP concentrations were significantly higher among patients with SAEs than those without them (median, 626.5 ng/L vs. 81 ng/L; P < 0.001). Adding NT-proBNP values to the CSRS did not significantly improve prognostication (c-statistic, 0.89 and 0.90; P = 0.12 for difference), regardless of SAE subgroup or whether the SAE was identified after the index ED visit. The net reclassification index shows that NT-proBNP would have correctly reclassified 3% of patients with SAEs at the expense of incorrectly reclassifying 2% of patients without SAEs. Our study was powered to detect a 3% difference in the area under the curve. The heterogeneity of outcomes and robust baseline discrimination by the CSRS will make improvements challenging. Although serum NT-proBNP concentrations were generally much higher among ED patients with syncope who had a 30-day SAE, this blood test added little new information to the CSRS. Routine use of NT-proBNP for ED syncope prognostication is not recommended. Physicians' Services Incorporated Foundation, Canadian Institutes of Health Research, and The Ottawa Hospital Academic Medical Organization.