Procalcitonin

• OMIM: 114130
• UniProt: P01258
• MGI: 2151253

Procalcitonin ( PCT) is a precursor of the hormone calcitonin and is formed in the C cells of the thyroid gland. Under certain conditions, such as infection or surgery, other cells produce such as liver or fat cells of this prohormone. 2005 was the Food and Drug Administration PCT critical in connection with the determination of additional laboratory values ​​for risk assessment of sepsis diseased patients. Therefore, in combination, since each infectious disease occurs far too complex in order to reduce to a single surrogate marker.

Clinical use of PCT in sepsis diagnostics

In critically ill patients with symptoms of acute systemic inflammation, it is often difficult to decide whether a sepsis or other non -related infectious disease ( systemic inflammatory response syndrome, SIRS ) is present. However, therapies and outcome of the disease may differ in patients with and without sepsis each other. Therefore, there is a great clinical need for diagnostic tools to differentiate between systemic inflammatory response syndrome (SIRS ), and a severe bacterial infection / sepsis.

PCT levels above 10 ng / ml indicate a high probability of a sepsis, PCT levels less than 10 ng / ml close sepsis but in no case out. In neonates, PCT increases physiologically. Therefore, apply to the first days of life other reference values ​​. The absolute level of PCT concentrations correlated with the severity of the inflammatory response and, accordingly, differs frequently in patients with systemic inflammatory response syndrome ( SIRS), sepsis, severe sepsis and septic shock. However, as the expression of different individual immune response is the same infection can be associated with different individual increases in PCT concentration.

PCT is also used to monitor the course of infection and prognosis of life-threatening septic infections and is used to monitor therapeutic measures.

A disadvantage of the PCT determination is the high cost in comparison with the classic signs of inflammation. How reliable procalcitonin a definition of sepsis on the one hand and non-infectious systemic inflammatory conditions allowed the other hand, is under discussion.

PCT for respiratory infections

In localized bacterial respiratory infections PCT levels are significantly lower than in septic extending infections. As in bacterial pneumonia or bronchitis are often PCT levels to from 0.25 to 0.5 ng / ml was found. Such low values ​​are comprehensible only with a sensitive PCT assay method. In an intervention study, PCT levels were sensitive to decide whether antibiotic therapy in patients was indicated with infections of the lower respiratory tract or not. The investigation results are not unambiguously positive: in some cases the antibiotics could be saved without the adverse effects were seen on the disease process, on the other hand, poor results have been reported. It was further found that the duration of antibiotic treatment could be shortened.

How are PCT values ​​to be interpreted?

In the interpretation must always be aware that non- infectious causes of elevated PCT can result in blood and that low values ​​do not rule out an infection or sepsis. An increase in PCT concentration indicates increased inflammatory activity, a decrease in the concentration, however, speaks for a reduction in inflammatory activity, which is a sign of a favorable prognosis. PCT not or only to a lesser extent responds to viral infections, chronic inflammatory diseases or autoimmune processes. Several studies have shown that SIRS patients often have lower PCT values ​​than patients with severe bacterial infections and sepsis.

Kinetics of PCT

The PCT concentration rises 2-3 hours after induction and reached its peak after 24 hours. Values> = 2ng/ml are highly associated with sepsis. After a successful therapeutic intervention PCT levels decline with a half -life of about 24 hours from again and thus show a positive prognosis on. Persistently high or even further increasing concentrations are an indicator of a poor prognosis.

PCT - protein and methods of measurement

Under normal metabolic conditions, the hormonally active calcitonin is synthesized in the C cells of the thyroid gland through specific intracellular proteolytic cleavage of the prohormone PCT and secreted. In bacterial infection and sepsis, however, intact PCT is found in the blood. As a site of synthesis in bacterial infection all organs are. PCT in vivo is very stable and has a half -life of about 24 hours. Also in vitro PCT is very stable, so that no special requirements are to be observed with regard to the pre-analysis or sample storage. For the in vitro determination of PCT are several immunoassays. With all methods PCT can be determined in serum and plasma. The time until the result is depending on the method 19-90 minutes.

PCT compared to CRP

PCT usually increases initially at earlier than CRP. In comparison to C- reactive protein, a biomarker commonly used, enables a PCT determination better discrimination of viral vs. bacterial infections. In infections, are responsible for the virus, PCT did not or hardly increases. This improves the decision-making on appropriate therapeutics.