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Introduction ⬇

Brain natriuretic peptide—B-type natriuretic peptide (BNP) and the N-terminal portion of its precursor form N-terminal propeptide of BNP (NT-proBNP)—includes hormones produced by the ventricles of the heart. Both BNP and NT-proBNP have been shown to increase in response to ventricular volume expansion (i.e., a decrease in left ventricular ejection fraction) and pressure overload.

Although they are markers of ventricular dysfunction, BNP and NT-proBNP cannot clearly differentiate between ventricular systolic or ventricular diastolic dysfunction. However, these markers are useful in diagnosing and assessing the severity of heart failure. These tests are particularly useful in the emergency department setting, where chest pain is a common presentation. Results for BNP and NT-proBNP are not interchangeable and cannot be compared. BNP and NT-proBNp levels are not used for diagnosing heart failure in patients with CKD. Chart 6.1 describes types of heart failures.

Normal Findings ⬆ ⬇

BNP: <100 pg/mL or <100 ng/L; NT-proBNP: <400 pg/mL or <400 ng/L (values tend to increase with age and are higher in women than men)

Clinical Alert

BNP level >400 pg/mL and NT-proBNP level >900 pg/mL is most consistent with heart failure, but other causes must be ruled out by clinical assessment and additional testing

Procedure ⬆ ⬇

  1. Obtain a plasma sample by venipuncture from a fasting patient. Use a lavender-topped (EDTA) tube. If a nonfasting sample is obtained, notify the laboratory. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.

  2. Prechill the tube at 4 °C before drawing a sample. After drawing the sample, chill the tube in wet ice for 10 minutes. Place the specimen in a biohazard bag.

Clinical Implications ⬆ ⬇

Increased BNP and NT-proBNP levels occur in:

  1. Diastolic dysfunction

  2. Decrease in left ventricular ejection fraction

  3. Heart failure

  4. Myocardial trauma

  5. CKD

  6. Acute pulmonary embolism

  7. Chronic obstructive pulmonary disease (COPD)

  8. Sepsis

  9. Burns

  10. Stroke

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose and need to fast. Assess for signs and symptoms indicating need for testing (e.g., chronic fatigue, cough, heart palpitations, hypertension).

  2. Withhold cardiovascular medications per healthcare provider’s order (e.g., β and calcium antagonists, cardiac glycosides, diuretic agents, vasodilators) before drawing the specimen.

  3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Have the patient resume medications and usual diet per healthcare provider’s order.

  2. Evaluate patient outcomes and monitor appropriately for heart failure.

  3. In collaboration with the healthcare provider, explain need for possible follow-up tests and medication therapy.

  4. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆

see Appendix E for drugs that affect test outcomes.