The recently published National Institute for Clinical Excellence (NICE) chronic heart failure (CHF) guideline¹ has recommended the use of brain natriuretic peptide (BNP) to help rule out the diagnosis of CHF, and quoted a sensitivity of 90–97%. Moreover, for purposes of medical audit, patients previously labelled as having CHF, but without a confirmation of the diagnosis, may need to be reassessed by measuring their plasma BNP concentrations. Recent papers highlighted that even BNP concentrations below accepted cut off values may actually be associated with elevated cardiovascular risk.² When clinicians consider whether to adopt a BNP assay in the diagnostic work up of CHF, one important concern is whether the false negatives could include severe CHF cases and thereby jeopardise their subsequent care through misdiagnosis. We explored this possibility by measuring N-terminal pro-BNP (N-BNP) in a cohort of subjects including those with a confirmed diagnosis of CHF and a wide range of New York Heart Association (NYHA) functional classes and healthy volunteers. Functional cardiac status was quantitatively graded according to aerobic exercise capacity, measured by peak oxygen consumption (V˙o₂).³ Although receiver operating characteristic curves and sensitivity/specificity methods are conventionally used to evaluate diagnostic techniques, for clinicians dealing with individual patients, the simpler method of plotting individual values relative to cut off values is more direct and more easily understood and is therefore employed in this study.

METHODS

Ninety six subjects participated in this study, including 86 consecutive stable CHF patients (diagnosed by practising heart failure specialists according to standard international and national heart failure guidelines: 64% had an underlying ischaemic aetiology, while the remainder had dilated cardiomyopathy (30%) and valve diseases) undergoing cardiopulmonary exercise testing (mean (SD) age 55.7 (12.0) years; 72 male; …