When someone is seriously ill and a doctor wants to distinguish between sepsis and other causes of the illness; to help guide treatment in a patient with sepsis
A blood sample taken from a vein in your arm
This test measures the amount of procalcitonin in the blood. Procalcitonin is made during the process of producing the thyroid hormone calcitonin. It is normally produced by special cells in the thyroid gland called C-cells and is present in low levels in the blood. However, it may also be made by other cells in the body when stimulated by certain disease processes, in particular whole body bacterial infection (systemic bacterial infection or sepsis) as opposed to just local bacterial infections. Other reasons for increased procalcitonin include infection from other causes, tissue damage due to events such as trauma, surgery, pancreatitis, burns, heart attack; and rapid and severe organ (kidney, heart, lung etc) transplant rejection.
Levels of procalcitonin in the blood increase rapidly and to high concentrations when a person has sepsis. They are not as particularly increased when a person has a viral infection or other illnesses which may have the same or similar symptoms as sepsis. Difference in stimulous gives procalcitonin the potential to be used to help detect severe bacterial infection at an early stage and to be able to distinguish between a bacterial infection and another cause of a serious illness.
How is it used?
The procalcitonin test is not available in all UK laboratories, and research is still being carried out to help us understand its role and how it should be used, in the management of septic patients. Studies have shown that it may help to discover whether a seriously ill person is developing sepsis. It has been studied mainly in Emergency Departments or intensive therapy units (ITUs) who have symptoms that may be due to sepsis. For diagnosis, procalcitonin is best used during the first day the patient is seen by the doctor. It may be used later on to follow how the patient responses to treatment.
Procalcitonin may sometimes be requested with other tests such as a CRP (C-reactive protein), blood culture, FBC(Full Blood Count), or CSF (cerebrospinal fluid) analysis to help detect or rule out sepsis, bacterial meningitis, or bacterial pneumonia in those who are seriously ill and in children with a fever of unknown origin.
Occasionally, a procalcitonin test may be used to follow the effectiveness of antimicrobial treatment.
When is it requested?
The procalcitonin test may be requested with other tests, when a seriously ill person has symptoms that suggest that they may have sepsis or severe bacterial infection. Procalcitonin is normally used as an early detection test, requested within the first day of hospital admission. Complications of sepsis may include:
- Chills, fever
- Feeling sick (nausea)
- Rapid breathing, rapid heartbeat
- Decreased urine output
More severe symptoms include inflammation throughout the body and formation of many tiny blood clots in the veins and capillaries. One or more organs may begin to stop working (multi-organ failure) and there may be a dangerous drop in blood pressure. Procalcitonin may be requested on several occasions to follow antimicrobial therapy in persons suspected of having sepsis.
What does the test result mean?
Low levels of procalcitonin in a seriously ill person indicates a low risk of sepsis and that they are unlikely to develop severe sepsis and/or septic shock, but a normal result does not exclude it. Low concentrations may suggest a local infection that has not yet spread to the whole of the body and become systemic or a systemic infection that is less than six hours old. It may also indicate that the person's symptoms are likely due to another cause, such as transplant rejection, a viral infection, or trauma – post-surgery or otherwise.
High levels indicate a high possibility of sepsis, that is, a higher likelihood of a bacterial cause for the symptoms. They also suggest a higher risk of progression to severe sepsis and then to septic shock.
Moderate elevations may be due to a non-infectious condition or due to an early infection and, along with other findings, should be reviewed carefully. Decreasing procalcitonin levels in a person being treated for a severe bacterial infection indicate a response to therapy.
Is there anything else I should know?
The procalcitonin test is not a replacement for other laboratory tests. Rather it is additional information that help earlier treatment.
Early detection of systemic bacterial infections, including bacterial pneumonia and bacterial meningitis, is important because they can be life-threatening and can be readily treated. However, the inappropriate use of antibiotics in cases where the illness is not bacterial in origin may cause delays in proper treatment, can encourage the development of antibiotic resistant organisms.
The procalcitonin test is being studied in additional populations, expanding beyond critically ill ITU patients. As more data are gathered, the clinical usefulness of procalcitonin will be better understood and its intended use(s) more fully defined.
Should a procalcitonin test be performed every time a person is seriously ill?