What are the uses for brain natriuretic peptide (BNP) and N-terminal prohormone of brain natriuretic peptide (NT-proBNP) testing in clinical practice?

Updated: Jan 08, 2018
  • Author: Donald Schreiber, MD, CM; Chief Editor: Erik D Schraga, MD  more...
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Answer

The following are summary recommendations regarding the use of brain natriuretic peptide (BNP) and NT-proBNP in clinical practice. [31, 32, 72, 73]

Care must be taken to interpret results in the context of the assay being used (BNP vs NT-proBNP), the performance characteristics of the particular manufacturer’s assay, and the patient’s confounding factors and comorbidities (including obesity and renal insufficiency).

BNP levels of less than 100pg/mL and of more than 500pg/mL have a 90% negative predictive value (NPV) and positive predictive value (PPV), respectively, for the diagnosis of congestive heart failure (CHF) in patients presenting with acute dyspnea. For intermediate levels between 100 and 500pg/mL, clinicians must also consider underlying left ventricular (LV) dysfunction, effects of renal insufficiency, or right ventricular (RV) dysfunction secondary to cor pulmonale or acute pulmonary embolism (PE).

In addition, if clinical suspicion is high for CHF but the natriuretic peptide levels are lower than expected, obesity or flash pulmonary edema should be considered. The information BNP testing provides should always be considered an adjunct in decision making about the patient’s treatment and disposition.

BNP and NT-proBNP levels are increased in the presence of renal insufficiency, NT-proBNP levels more so than BNP. NT-proBNP levels can be elevated simply on the basis of the normal age-related decline in estimated glomerular filtration rate (GFR). When the calculated GFR is less than 60mL/min, NT-proBNP levels can be extremely elevated, and their utility in diagnosing CHF in this situation is unclear. For BNP, increasing the rule-out cutoff value to 200pg/mL is recommended when the GFR is less than 60mL/min.

Natriuretic peptide levels may be elevated in the intermediate range in chronic pulmonary disease when RV overload occurs. NT-proBNP and BNP levels may also be elevated in acute PE. Although elevations are not diagnostic for PE, high levels are predictive of a worsened prognosis, particularly when in conjunction with elevated troponin levels. In about 20% of patients with pulmonary disease, natriuretic peptide levels are elevated. Elevations in this context imply CHF, combined CHF and lung disease, cor pulmonale, or acute PE.

BNP and NT-proBNP may be used to identify patients with diastolic dysfunction, but cutoff points remain to be age adjusted and subsequently related to diastolic filling abnormalities.

Patients with a body mass index (BMI) greater than 30kg/m2 have low levels of BNP and NT-proBNP. Although serial determinations are likely to be useful, a diagnosis of CHF must be carefully considered in the appropriate context, even when levels are below cutoff levels.

Natriuretic peptides are independent predictors of mortality in CHF. Increased or persistent elevation in natriuretic peptide levels despite treatment suggests progression of disease or resistance to treatment. In the acute setting, failure of BNP or NT-proBNP levels to decrease with treatment is a poor prognostic factor that requires intensification of treatment.

Natriuretic peptide levels should not be measured daily. One suggested algorithm is to measure levels on admission, after 24 hours of treatment, and at discharge. Decreased natriuretic peptide levels are predictive of excellent outcomes.

BNP levels should not be measured while patients are receiving recombinant infusions of BNP (eg, nesiritide). However, NT-proBNP levels are not affected by nesiritide.

In acute coronary syndrome (ACS), troponin, creatine kinase–MB isoenzyme (CK-MB), and myoglobin are markers of myocardial necrosis and are highly predictive of adverse cardiac events. As a marker of LV dysfunction, natriuretic peptides are not helpful in diagnosing myocardial ischemia and ACS. However, BNP and NT-proBNP levels may be useful for risk stratification in patients with ACS, and they may predict clinical CHF. A multimarker approach may improve risk stratification.

BNP or NT-proBNP screening is not appropriate for low-risk, asymptomatic patients. Screening may have some value in populations with certain risk factors (eg, previous myocardial infarction, diabetes, long-standing uncontrolled hypertension); however, echocardiography is likely to remain the study of choice for assessing LV function.


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