European Journal of Heart Failure Advance Access originally published online on October 6, 2009
European Journal of Heart Failure 2009 11(11):1043-1049; doi:10.1093/eurjhf/hfp127
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Adjusting for clinical covariates improves the ability of B-type natriuretic peptide to distinguish cardiac from non-cardiac dyspnoea: a sub-study of HEARD-IT
1 Division of Cardiology, University of Utah Health Sciences Centre, 30 N 1900 E, Room 4A100, Salt Lake City, UT 84132-2401, USA
2 Division of Epidemiology, University of Utah, Salt Lake City, UT, USA
3 Department of Emergency Medicine, University of Cincinnati, Cincinnati, OH, USA
4 Department of Emergency Medicine, Cleveland Clinic Foundation, Cleveland, OH, USA
5 Division of Cardiology, San Diego VA Medical Centre, San Diego, CA, USA
6 Research Service, San Diego VA Medical Centre, San Diego, CA, USA
* Corresponding author. Tel: +1 801 585 1686, Fax: +1 801 581 7735, Email: andrew.michaels{at}hsc.utah.edu
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Abstract |
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Aims: We sought to create a model that adjusts B-type natriuretic peptide (BNP) for specific covariates to better distinguish cardiac from non-cardiac dyspnoea.
Methods and results: HEARD-IT was a multicentre, prospective study of the diagnostic utility of acoustic cardiography in the emergency department. Dyspnoeic patients more than 40 years were eligible. Two cardiologists independently adjudicated the HF outcome. Using logistic regression, a model adjusting BNP for pertinent covariates was developed (n = 740). The mean age was 66 ± 13 years. Age, gender, ethnicity, body mass index, blood urea nitrogen, and creatinine affected BNP levels independently of HF. The model adjusting BNP for these covariates improved the area under receiver operator characteristic curve for HF compared with BNP alone (0.948, 95% CI 0.934–0.963 vs. 0.937, 95% CI 0.920–0.954; P = 0.004). Net reclassification improvement, a novel metric of model performance, was 3.5% for those without HF (P = 0.05) compared with conventional, unadjusted BNP cut-offs. Thirteen of 116 (11%) patients without HF, but with unadjusted BNP values 
100 pg/mL, were correctly reclassified as not having HF with the adjusted BNP model.
Conclusion: Adjusting BNP for important covariates may improve its ability to distinguish cardiac from non-cardiac dyspnoea.
Key Words: Natriuretic peptides • Heart failure • Dyspnoea • Cardiovascular disease • Net reclassification improvement
Received May 18, 2009; Revised July 27, 2009; Accepted August 24, 2009