BNP (pro-BNP)

Norm
Pro-BNP 7.0–12.2 pmol/l
BNP       6.5–10.2 pmol/l

Synonyms: Brain natriuretic peptide, Human brain natriuretic peptide.
Similar substances: ANP, pro-ANP, NT-pro-BNP, β-ANP, CT-ANP, natriuretic peptides.
Serum
Red cap

BNP indicator (brain natriuretic peptide) is elevated in patients with heart failure. The laboratory pro-BNP or BNP indicator is elevated even in early stages of heart failure (for example, in NYHA class 1 heart failure). Other natriuretic peptides, such as ANP (atrial natriuretic peptide), have similar clinical interpretation possibilities as BNP. However, ANP is not as sensitive and specific as an indicator. In this group, the most specific and stable indicator is considered to be pro-BNP-NT.

The heart is a neuroendocrine organ. BNP and ANP are heart hormones that protect the heart muscle from increased mechanical load or electrolyte imbalance. They are antagonists of the renin-angiotensin-aldosterone system. In primary health care, the determination of pro-BNP could be useful in screening patients with stable heart failure. The pro-BNP indicator has a particularly good prognostic specificity (the higher the pro-BNP, the worse the prognosis). Determining pro-BNP cannot replace echocardiography or radionuclide ventriculography. These tests and the laboratory pro-BNP indicator reflect different aspects of the pathological process. All patients suspected of having cardiac failure must undergo an echocardiogram (along with determining pro-BNP or BNP). Determining pro-BNP provides additional information, helps evaluate the course of treatment, and helps select patients for ACE inhibitor therapy. If pro-BNP decreases with ACE inhibitor therapy, it indicates a good therapeutic response and a better prognosis. Pro-BNP may increase during myocardial infarction. Typically, this increase lasts for the first 2–3 days. The duration and degree of increase are directly related to the unfavorable prognosis of myocardial infarction. According to the New York Heart Association (NYHA) classification, there are 4 degrees of heart failure (see table). The BNP indicator reacts in the earliest stage, even before clear clinical signs of failure are present. The BNP indicator, its concentration in the blood, increases proportionally with the stage of cardiac failure. The indicator tends to increase in hypertensive disease. Sometimes BNP increases in patients without signs of heart failure – systolic dysfunction, renal insufficiency. Pro-BNP is a more specific indicator (for evaluating heart failure) than BNP or any other natriuretic peptide (ANP, NT, etc.).

Elevation
• Symptomatic and asymptomatic heart failure (the indicator correlates with the prognosis and course of the pathology);
• Systolic dysfunction;
• Left ventricular hypertrophy;
• Increased atrial pressure;
• Increased pulmonary capillary pressure;
• Prioritization for heart transplantation (but a worse prognosis is likely if pro-BNP is high);
• Correlates with left ventricular hypertrophy and heart wall size (septum, posterior wall);
• Myocardial infarction (the higher the value and the longer the increase in pro-BNP in the blood, the worse the prognosis, higher mortality);
• Sometimes – hypertensive disease;
• Other pathological conditions: valve stenosis, tachycardia, increased central venous pressure;
• Sometimes – renal insufficiency;
• Sometimes – liver cirrhosis.

Normal
• Finding a normal value indicates a very low probability of heart pathology.

Relative decrease
• Good therapeutic response in the background of previous enlargement;
• Control with ACE inhibitors treatment.

Source | Handbook of Basic Laboratory Tests | Doctor of Medical Sciences Gintaras Zaleskis