Clinical Health Updates

NT-BNP reduces cost and rehospitalization rates in dyspneic patients.

Clinical Question:
Does the use of B-natriuretic peptide testing improve clinical and economic outcomes in patients hospitalized with dyspnea?

Bottom Line:
The use of the N-terminal B natriuretic peptide (NT-BNP) reduces the cost of care, the length of the emergency department (ED) visit, and the likelihood of rehospitalization when used in the evaluation of patients presenting to the ED with dyspnea. However, it does not reduce mortality or hospital length of stay.

Reference:
Moe GW, Howlett J, Januzzi JL, Zowall H; Canadian Multicenter Improved Management of Patients With Congestive Heart Failure (IMPROVE-CHF) Study Investigators. N-terminal pro-B-type natriuretic peptide testing improves the management of patients with suspected acute heart failure: primary results of the Canadian Prospective Randomized Multicenter IMPROVE-CHF study. Circulation 2007;115(24):3103-3110.

Study Design:
Randomized controlled trial (single-blinded)

Synopsis:
Sometimes new tests are just, well, more tests. Ultimately, we should not only ask whether a new test is accurate (disease-oriented evidence), but also ask whether the use of the test improves clinical outcomes. This is one of the few studies to do just that. The authors of this study, sponsored by the test manufacturer, identified 534 adults presenting to a Canadian ED with dyspnea. Patients with advanced renal disease, acute myocardial infarction, malignancy, and dyspnea due to “clinically overt” origins, such as pneumothorax or chest trauma, were excluded, leaving 500 patients for the final study. The ED physician was asked to commit to a diagnosis of heart failure or no heart failure without knowledge of NT-BNP. Patients were then randomized to receive care guided by NT-BNP or care without knowledge of that test result. The results of the test were given to the ED physician and all physicians involved in the patient’s care, and the test was repeated 72 hours later in hospitalized patients. The final diagnosis of heart failure (present in 46% of patients) was made by 2 cardiologists who were given all of the clinical data except the NT-BNP result (having knowledge of the NT-BNP result as part of the reference standard would bias the study and inflate the accuracy of the test).

Patients were followed up at 60 days for clinical and economic outcomes. Groups were balanced at the start of the study, and analysis was by intention to treat. Patients in the group whose care was informed by the NT-BNP result had a shorter ED visit (5.6 vs 6.3 hours; P = .03), lower total direct cost (CAN $5180 vs $6129; P = .02), and fewer rehospitalizations (13% vs 20%; P = .046). There was also a nonsignificant trend toward less use of outpatient diagnostic testing, but no difference in hospital length of stay or mortality rates. Benefits were greater in patients with an intermediate clinical probability of heart failure; that is, those for whom the diagnosis was in question. The researchers also looked at the accuracy of clinical judgment alone versus judgment supplemented by the NT-BNP result, and found that the test increased the accuracy of diagnosis (area under the receiver operating characteristic curve 0.90 vs 0.83, where 1.0 = a perfect test and 0.5 = a worthless test).