BNP, or brain natriuretic peptide, is a heart produced hormone found in blood. It is secreted due to abnormal stretching of the heart muscle. Its levels are known to be the indicator of the state of the cardiovascular system, and are of big assistance when diagnosing the severity of a heart failure and conditions such as diastolic dysfunction. Normally, a low amount of this hormone is always present in our blood; however, an elevated BNP is far from normal.

Causes of Elevated BNP

1. Cardiac Causes

• Heart failure
• Diastolic dysfunction
• High blood pressure accompanied with hypertrophy of the left ventricle
• Acute coronary syndrome - a term referring to a couple of heart conditions such as myocardial infarction and angina pectoris
• Arrhythmia
• Heart valve disease (mitral valve prolapse, aortic stenosis)

2. Non-Cardiac Causes

• Primary or secondary pulmonary hypertension
• Obstruction of blood vessels in the lungs - pulmonary embolism
• COPD (chronic obstructive pulmonary disease) followed with respiratory failure and cor pulmonale
• Overactivity of the thyroid gland - hyperthyroidism
• Sepsis
• Chronic and acute kidney trauma
• Water and sodium retention caused by medications (Avandia®, Actos®, etc.)
• Water and sodium retention caused by kidney dysfunction

Use of BNP Test

Now we know the causes of elevated BNP, so what can a BNP test be used for?

1. Heart Failure

BNP testing helps a lot when it comes to diagnosing heart failure. It helps determine whether a patient is in need of echocardiogram, and helps to decide whether changes in therapy are needed for patients who are already subjected to heart failure treatments.

• BNP assay indicates the presence of left ventricular systolic dysfunction, thus minimizing the number of people needing an echocardiogram.
• BNP values are compatible with the Goldman Specific Activity Scale of Heart Failure, along with the New York Heart Association (NYHA) Classification of Heart Failure.
• Low amount of this hormone rules out heart failure as a possible condition, while the extremely high amount of it confirms the possibility of a heart failure. However, if the BNP levels has intermediate values, an additional examination is necessary.
• BNP testing aids the triage of patients showing the symptoms of heart failure, as well as the screening of patients who are at a high risk of developing heart failure.
• A few preliminary studies have proven that different concentrations of BNP can help distinguish heart decompensation from pulmonary disease.
• Another preliminary study has proven that the home finger prick BNP test can help determine the severity of a heart failure, and the potential risk of acquiring it.

A study revealed that the levels of BNP were in high correlation with these outcomes:

• Good outcomes came for patients whose BNP levels were decreasing during their time at the hospital.
• Patients who died in the hospital, or were readmitted within a month of their release, had no to minimal decrease of BNP levels, or even had increased BNP levels.
• The last BNP measurement before the hospital discharge was the most trustworthy factor of foreseeing the outcome.

2. Other Potential Clinical Applications

• Causes of elevated BNP don't have to be related to a heart failure. In fact, increased levels of it have been known to predict possible death and cardiovascular diseases in people without heart failure. 
• BNP assessment helps recognize patients who bear a risk of developing arrhythmia and stroke.
• Natriuretic peptides are strong indicators of mortality in people suffering from acute chest pain.
• It plays a big role in predicting the mortality of cerebrovascular accident.

Information About BNP Test

1. When a BNP Test Will Be Ordered?

A doctor chooses to order a BNP or NT-proBNP test in case a patient experiences symptoms that match symptoms of heart failure, including:

• Fatigue
• Breathing difficulties, and shortness of breath
• Swelling of the abdomen and lower parts of the body (legs, ankles, feet)

The test can be enforced directly in the emergency room if a person has alarming symptoms of heart failure that require rapid establishing of diagnosis.

BNP or NT-proBNP test is re-done every few months as long as the patient is receiving the heart failure therapy as a means of checking its effectiveness.

2. How to Prepare for a BNP Test

Don't eat or drink anything, with the exception of water, 8 to 12 hours prior to a BNP test. Closely follow your doctor's orders, and stop taking some heart medications before undergoing the exam in case he or she advises you to. Feel free to talk to your doctor about any test-related concerns you might have, such as its necessity, risks, procedure, and results.

3. How It Is Done

The medical worker who draws your blood will do the following:

• Stop your blood flow by wrapping an elastic band around your upper arm, thus making your veins appear larger and easier to penetrate.
• Clean the puncture area with a little bit of alcohol.
• Penetrate the vein with a needle, fasten a tube to it and fill it with blood.
• Re-establish the blood flow by removing the band from your arm after collecting a sufficient amount of blood.
• Put a cotton ball over the puncture area immediately after the removal of the needle.

4. BNP Test Results Interpretation

Considering the fact that there are many causes of elevated BNP, reading of brain natriuretic peptide levels can be a complicated process. However, all doctors accept the use of 2 values when interpreting it: a lower one that rules out heart failure as a possible condition, and a higher one which indicates its existence.

If a BNP value is less than 100 pg/mL, a possibility of heart failure is excluded. At the same time, the value of 400 pg/mL and more suggests a 95% probability of heart failure. Intermediate values go from 100 pg/mL to 400 pg/mL, and if such came back from the test, an additional examination is required. BNP is also regularly found in blood, and its normal range varies from 0.5 pg/mL to 30 pg/mL.