BMJ  2004;328 (29 May), doi:10.1136/bmj.328.7451.0-f

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BNP improves outcomes in evaluation of dyspnoea

Question Does use of the test for B-type natriuretic peptide (BNP) in the diagnosis of acute dyspnoea improve patients' outcomes?

Synopsis Too often, new tests are introduced without a careful examination of their effect on patient oriented outcomes. Accuracy alone is not reason enough to adopt a test; a more important reason is that its use helps patients live better or longer lives. We should also know whether is adds or reduces cost. There is previous convincing evidence that B-type natriuretic peptide is accurate in diagnosing heart failure in patients presenting with acute dyspnoea ( N Engl J Med 2002;106: 416-22). This latest randomised controlled trial (single blinded) study is the first to look at the larger impact of this test's use in clinical practice. Of 665 consecutive adults presenting to a Swiss emergency department with acute dyspnoea, 452 met the inclusion criteria. Patients with an obvious traumatic cause, serum creatinine levels greater than 2.8 mg/dl, cardiogenic shock, or who requested transfer to another hospital were excluded. The mean age of patients was 71 years, and half were women. Patients were randomly assigned (allocation concealed) to usual care supplemented by a rapid BNP level, or the usual diagnostic protocol without knowledge of BNP level. Clinicians were advised that a BNP level less than 100 pg/ml made heart failure unlikely, a result greater than 500 pg/ml made heart failure very likely, and that intermediate values required additional information and clinical judgment to make the diagnosis. The BNP was not measured during any subsequent hospitalisation. All patients underwent a careful history and physical examination, electrocardiogram, chest x ray, and blood tests other than BNP. Echocardiography and pulmonary function testing were strongly recommended for all patients, whether or not they were admitted, although the percentage actually having the tests was not reported. Outcomes were assessed by a group blinded to treatment assignment. The BNP test provided additional information that clearly improved patient outcomes. The likelihood of admission to the hospital was lower in the BNP group (75% v 85%; P = 0.008; absolute risk reduction 10%; number needed to treat (NNT) = 10), as was the likelihood of admission to the intensive care unit (15% v 24%; P = 0.01; NNT = 1). Patients in the BNP group were treated more quickly (63 v 90 mins; P = 0.03), spent less time in the hospital (8 v 11 days; P = 0.001), and their care cost less ($5410 v $7264; P = 0.006) than those whose physicians did not have that test result. There was no difference in either in-hospital or 30 day mortality and no difference in 30 day readmission rates.

Bottom line Knowing the level of B-type natriuretic peptide during initial evaluation in the emergency department is associated with more rapid initiation of appropriate treatment, less need for hospitalisation and intensive care, a shorter length of stay, and lower costs. The next question is whether the BNP can replace other tests like the chest x ray or echocardiogram for some patients.

Level of evidence 1b (www.infopoems.com/levels.html). Independent blind comparison of an appropriate spectrum of consecutive patients, all of whom have undergone both the diagnostic test and the reference standard; or a clinical decision rule not validated on a second set of patients.

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Mueller C, Scholer A, Laule-Kilian K, et al. Use of B-type natriuretic peptide in the evaluation and management of acute dyspnea. N Engl J Med 2004;350: 647-54[Abstract/Free Full Text].

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^* Patient-Oriented Evidence that Matters. See editorial ( BMJ 2002;325: 983[Free Full Text])

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