Procalcitonin | Laboratory research

Procalcitonin (PCT) Is a polypeptide that is an inactive precursor to calcitonin. Normally, PCT is produced in thyroid C cells from preprocalcitonin, under the influence of calcium-dependent factors. In healthy individuals, PCT is fully converted to calcitonin and practically does not pass into the bloodstream. In early infancy, an increase in PCT levels is normal.

In acute bacterial infections and sepsis, massive production of endotoxins, increased levels of protein cytokines (IL-6 and TNF-α) leads to an increase in PCT synthesis, not only in the thyroid gland, but also extrathyroid: primarily in leukocytes, leukocytes, and leukocytes. In neuroendocrine cells. All this leads to a rapid and sharp increase in PCT levels (already 6-12 hours after the spread of the pathological process), against the background of maintaining calcitonin levels.

It should be remembered that the level of PCT increases only in the spread of bacterial infection (sepsis) and reflects its severity, local processes do not cause an increase in the level. Thus, not only the increase in quantity but also the growth rate and dynamics of procalcitonin levels are of diagnostic value. However, it should be noted that the increase in PCT does not occur in fungal and viral infections, allergic and autoimmune diseases, which allows a differential diagnostics.

The half-life of PCT is 25-30 hours, which makes it possible to use it as a marker of the effectiveness of antibiotic therapy (after successful surgical treatment or antibiotic therapy, the level of procalcitonin in the blood decreases rapidly, by 30-50% per day). On the other hand, with constant increases in procalcitonin levels for more than 4 days, treatment adjustment is required. If there is no rapid decrease in procalcitonin levels after treatment, the prognosis of the disease is doubtful. Constantly increasing PCT rates indicate a poor prognosis of the disease. In acute pancreatitis, PCT is an indicator of the severity of the disease and infectious complications. According to some authors, an increase in procalcitonin levels above 1.8 ng / ml indicates the development of infectious complications (susceptibility - 80-95%, specificity - 88-93%).

When should we take a test for procalcitonin?

The procalcitonin test is informative in the following cases:

• Diagnosis of bacteremia and septicemia in adults and children (including neonates);
• Diagnosis of complications of urinary tract infection in children;
• Diagnosis of bacterial infection in neutropenic patients;
• Septic shock diagnostics, risk stratification and monitoring;
• Diagnosis of systemic secondary infection during surgery, severe trauma, burns, and multiorgan failure;
• Differential diagnostics of bacterial and viral meningitis;
• Differential diagnostics of outpatient bacterial or viral pneumonias;
• Monitoring the therapeutic response to antibacterial therapy.

How to prepare for the test?

A test is required on empty stomach .

Research material

Venous blood

Possible interpretation of the results

At the initial diagnostics, the presence of growth and growth dynamics is assessed, and to evaluate the effectiveness of treatment - monitoring of normalization of procalcitonin levels, period of occurrence dynamics and maintenance of normal levels.

Increased procalcitonin levels:

• Sepsis;
• Severe bacterial infection;
• Ineffective antibacterial therapy for bacterial infection;
• The spread of the infectious process.

There are clinical conditions when procalcitonin levels are high despite the absence of infection:

• After severe injury - on the first day;
• Large surgery;
• Burns;
• Treatment with drugs that stimulate the release of inflammatory cytokines;
• Small cell lung cancer;
• Thyroid carcinoma;
• Newborns during the first 48 hours of life;
• Strong or prolonged cardiogenic shock.