What is BNP (B-Type Natriuretic Peptide) test? 

A BNP test is performed to determine the level of a hormone called BNP in your blood. BNP helps in the regulation of blood volume and is produced in the left ventricle (left lower chamber) of our heart. However, higher than normal BNP levels in the bloodstream could be an indication of heart failure. This is because when the left ventricle stretches, the level of BNP in the blood rises significantly. This rise in BNP indicates that the heart is getting overworked in order to meet the body’s demand for oxygen. The primary feature of heart failure is that in this state the heart does not remain strong enough to meet the body’s needs. It can also indicate other issues related to our circulatory system. 

It is important to note that the level of BNP remains higher in women than in men. 

  1. Why is a BNP (B-Type Natriuretic Peptide) test performed?
  2. How do you prepare for a BNP (B-Type Natriuretic Peptide) test?
  3. How is a BNP (B-Type Natriuretic Peptide) test performed?
  4. BNP (B-Type Natriuretic Peptide) test results and normal range

If a doctor suspects that a patient is showing symptoms of heart failure, he/she may suggest a BNP test. The symptoms of heart failure include:

Apart from checking for heart failure, this test is also performed to determine the severity of heart failure and check the effectiveness of the medicines being given for heart failure.

Since elevated BNP is also associated with lung, kidney and liver diseases, a BNP test rules out the possibility of conditions associated with these organs too. 

You will not require any preparations before this test. However, you should inform your doctor if you are on any medications as some drugs may affect the results of this test.

In order to conduct the test, a blood sample is required. A lab technician will draw the required amount of sample from a vein in your arm by injecting a sterile needle. The sample will be collected in an appropriate container/tube and sent to a laboratory for analysis.

Some people feel temporary lightheadedness after the test or notice bruising on the injection site. Some possible problems and risks associated with taking a blood sample are: 

  • Difficulty in obtaining the sample
  • Excessive bleeding at the site from where the blood is drawn
  • Haematoma (accumulation of blood under the skin)
  • Infection at the site where the needle is inserted

However, these risks can easily be reduced if proper precautionary measures are taken. 

Normal results:

Normally BNP values remain higher in women than in men and they increase gradually with age. However, they may still stay within the normal reference range unless there is heart failure.

A doctor will interpret the results according to your age and gender.

The normal reference range for most individuals is: <100 picograms/millilitre (pg/mL)

This indicates that you do not have heart failure. If the cause of symptoms is being determined, then it will be concluded that the symptoms are occurring due to another condition and not heart failure. 

It is important to note that normal results may vary among different laboratories due to differences in the measurements and testing methods. Therefore, it is essential to discuss the results with the doctor in order to get an accurate interpretation. 

Abnormal results:

Results > 100 pg/mL indicate abnormal results. An increase in BNP level is indicative of heart failure. The higher the value, the more the severity of heart failure. 

However, a rise in the BNP level may also be seen in the presence of the following conditions:

The test may be repeated to monitor the effectiveness of the treatment being given. If BNP levels remain high despite the treatment, it indicates disease progression or resistance to treatment. 

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

References

  1. Bock JL. Cardiac injury, atherosclerosis, and thrombotic disease. In: McPherson RA, Pincus MR, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017: chap 18.
  2. Felker GM, Teerlink JR. Diagnosis and management of acute heart failure. In: Zipes DP, Libby P, Bonow RO, Mann L, Tomaselli GF, Braunwald E, eds. Braunwald’s Heart Disease: A Textbook of Cardiovascular Medicine. 11th ed. Philadelphia, PA: Elsevier Saunders; 2019: chap 24.
  3. Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.
  4. Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
  5. Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St Louis: Mosby Elsevier.
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