What is PCT?

By | 9 May 2021

PCT, one of the laboratory tests, is performed to measure the amount of procalcitonin in the blood. The PCT test, also known as the procalcitonin test, is often used in the presence of suspected bacterial infection and in cases of life-threatening sepsis. Sepsis, also known as blood poisoning among people, can cause single or multiple organ failure and may pose a life-threatening risk. It occurs as a result of bacteria that cause infection in the body, mixing with the blood. In case of suspicion of sepsis, the test is applied to understand whether the existing bacterial infection has spread. Procalcitonin, which is expected to be at a very low level at the blood level under normal conditions, is a component that plays a role in the production of the hormone called calcitonin, which is produced by the thyroid gland, lung, and liver. Procalcitonin, a peptide (an amino acid with antibacterial and anti-inflammatory effect) secreted naturally in the body, also increases in severe bacterial infections. PCT, which is also considered a biological indicator in this sense, is rapidly synthesized in the thyroid gland, lung, and liver in cases that are severe enough to affect the life functions of the person. The test, which is performed to measure the procalcitonin level at the blood level, has an important place in the diagnosis of sepsis in emergency and intensive care units. Before explaining what PCT high and low mean, what is PCT should be understood well.

What is PCT?

PCT, known as procalcitonin, is a type of blood test. PCT, which is at an immeasurably low level in healthy individuals, is a substance that is rapidly produced by neuroendocrine tissue of organs such as the lung and liver, especially C cells in the thyroid gland, as the infections in the body cause tissue damage. The PCT test, which is used to differentiate bacterial and non-bacterial infections, is used to measure the level of procalcitonin in the blood. The PCT test performed in suspicious cases in the presence of infectious diseases, intensive care units, and emergency services have a high sensitivity in this sense. The PCT test has the feature of being a biomarker or, in other words, a biological indicator. A high PCT value indicates the presence of systemic infection or sepsis in the person. The higher the value, the higher the probability. The procalcitonin level, which does not show a significant increase in the presence of the virus, increases significantly in systemic infections, especially in the presence of sepsis, which is known as blood poisoning among the public and is caused by the contamination of the bacteria that cause the infection. It has an important place in the diagnosis of sepsis, which causes death due to single or multiple organ failure. İt is also used as a tool for directing and optimizing antibiotic therapy. In other words, the PCT value above a certain level guides the physician in the use of antibiotics. The response to antibiotic treatment is also evaluated according to the PCT level. Antibiotic treatment is rearranged based on the peak levels of procalcitonin in the blood level. Procalcitonin, which increases and decreases faster than CRP (C reactive protein), which is another biomarker in the blood, is of great importance for the early diagnosis and treatment of conditions such as sepsis. “What does PCT mean?” The question can be answered in this way.

What is low PCT?

Procalcitonin, which is at an immeasurably low level in healthy individuals, is produced largely in the thyroid gland and in smaller amounts in the lung and liver. In the presence of severe bacterial infection, a low PCT value, which rises rapidly within 2 to 4 hours, indicates that there is no bacterial infection in the body. In other words, a PCT value between 0 and 0.05 µg / L is considered normal. The low PCT value is an important biomarker that helps to rule out the suspicion of sepsis. Low procalcitonin levels can also be seen in virus-induced infections if the transplanted organ is not accepted by the body and postoperative trauma.

What is the PCT elevation?

Procalcitonin is synthesized from the neuroendocrine tissue of organs such as the lung and liver, especially C cells in the thyroid gland, in the presence of sepsis known as bacterial-induced systemic infection and blood poisoning. The PCT value, which is normally expected to be in the range of 0 to 0.05 µg / L, rises rapidly between 2-4 hours in the presence of such conditions. In other words, PCT elevation indicates the presence of bacterial infections in the body and the possibility of sepsis. A PCT value of 0.5 to 2 µg / L indicates the possible presence of infection, a value of 2 to 10 µg / L indicates a possible case of sepsis. A PCT value of 10 µg / L and above indicates the presence of strong sepsis. PCT test values ​​performed with suspicion of respiratory tract infection are very likely to be in the range of 0.75 to 10+ µg / L, while the PCT value above 0.25 µg / L is an indication that antibiotic treatment should be initiated. If the PCT value falls to the range of 0.1 to 0.25 µg / L in suspected respiratory tract infection, the PCT value is re-checked within 6 to 24 hours, even if antibiotic use is discontinued. In the procalcitonin test performed for suspicion of sepsis, values ​​between 0.5 and 10+ µg / L most likely indicate the presence of sepsis, while the same values ​​indicate the need for antibiotics. The decline of the PCT test result after antibiotic treatment to a value in the range of 0.25 to 0.5 µg / L makes the possibility of sepsis excluded. These values ​​also indicate that antibiotic therapy can be discontinued. Considering the PCT levels of the patient whose treatment was prescribed for sepsis, the physician evaluates the patient in terms of clinical course after the end of antibiotic use. The PCT value may also be high due to sepsis, acute organ failure, thyroid cancer, meningitis, pneumonia, urinary tract infection, and the side effects of some drugs.

Why is the PCT test done?

The PCT test is a laboratory test for rapid results in emergency cases. The physician often requests tests such as C-reactive protein (CRP), cerebrospinal fluid analysis defined as CSF (Cerebrospinal fluid), blood culture, and blood count. The physician makes the evaluation of other test results, especially the PCT test, in the light of clinical findings. Procalcitonin test is performed especially in intensive care units and emergency rooms with suspicion of sepsis. The test does not require any preparation, such as fasting, and the PCT test is performed with a blood sample taken from a vein in the arm. The PCT test is generally performed in the presence of suspicion of bacterial infection, for the differential diagnosis of some diseases, for determining the type and dose of antibiotics to be used against infection, for early diagnosis of diseases such as pneumonia and meningitis, and to determine whether the existing infection is caused by a virus or a bacterium. The test without any side effects can also be done in the following situations:

  • Tachycardia, or heart palpitations as it is popularly known,
  • High fever,
  • Low blood pressure defined as hypotension,
  • Hyperventilation, in other words, rapid or deep breathing,
  • Nausea,
  • Decrease in the amount of urine,
  • Monitoring the response of the followed bacterial infection to the treatment.

High levels of procalcitonin synthesized by the neuroendocrine tissue of organs such as the thyroid gland, lungs, and liver are observed in the presence of bacterial infection and especially sepsis cases. However, the result of the PCT test is not an indicator that the procalcitonin level increases depending on which disease. Therefore, clinical findings accompanying PCT values ​​are also very important. We wish you healthy days.


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