Procalcitonin TechNotes

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Procalcitonin TechNotes.

Procalcitonin (PCT) is a small protein comprising 116 amino acid residues (a.a.r.) with molecular weight of about 13 kDa. For the first time amino acid sequence of PCT was described by Moullec et al. in 1984 (1). PCT belongs to a family of related proteins (CAPA peptides family), which includes calcitonin gene-related peptides I and II, amylin, adrenomodulin and calcitonin. Like other peptides of CAPA family PCT appears from the precursor molecule - preprocalcitonin comprising 141 a.a.r. by removal 25 a.a.r. from N-terminus.

PCT is produced normally in C-cells of the thyroid glands. It undergoes successive cleavages to form three molecules: N-terminal fragment (N-terminal PÑÒ) (57 a.a.r.), Calcitonin (32 a.a.r.) and Katacalcin (21 a.a.r.).
In 1993 elevated level of PCT in patients with system infection of bacterial origin was reported (2) and now PCT is considered to be the main marker of disorders accompanied by systemic inflammation and sepsis. The diagnostic value of PCT is important due to the close correlation between PCT concentration and the severity of inflammation (3). It was shown that “inflammatory” PCT is not produced in C-cells. Cells of neuroendocrine origin are presumably the source of PCT during inflammation (4). 

In some cases raising PCT concentration may be induced by factors independent of sepsis and infection. Surgery, polytrauma, heat shock, burn injures, cardiogenic shock also lead to increase of PCT level (3). The mechanism of the increasing level of PCT in these cases is not defined clearly. The importance of monitoring of PCT levels' changes after cardiac surgery or heart transplantation for differentiating acute graft rejection from bacterial or fungal infections was confirmed in multiple studies (4).

Thus, the diagnostic value of PCT is very high and usefulness of PCT quantification in patients’ blood using specific monoclonal antibodies is very perspective and quite obvious (4, 5).