Procalcitonin

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Procalcitonin (PCT) is a precursor of the hormone calcitonin, which is involved with calcium homeostasis, and is produced by the C-cells of the thyroid gland. It is there that procalcitonin is cleaved into calcitonin, katacalcin and a protein residue. It is not released into the blood stream of healthy individuals. With the derangements that a severe infection with an associated systemic response brings, the blood levels of procalcitonin may rise to 100 ng/ml. In blood serum, procalcitonin has a half-life of 25 to 30 hours.

Measurement of procalcitonin can be used as a marker of severe sepsis and generally grades well with the degree of sepsis,^[1] although levels of procalcitonin in the blood are very low. PCT has the greatest sensitivity (85%) and specificity (91%) for differentiating patients with SIRS from those with sepsis, when compared with IL-2, IL-6, IL-8, CRP and TNF-alpha.^[2] However, the test is not routinely used and has yet to gain widespread acceptance.
In a comprehensive Meta-Analysis in 2007 the diagnostic accuracy of procalcitonin as a marker to differentiate sepsis from other non-infectious causes of systemic inflammatory responses was estimated including 18 studies (14 phase 2 and 4 phase 3 studies). ^[3] In this review the overall diagnostic performance of procalcitonin was low. The authors concluded that procalcitonin cannot reliably differentiate sepsis from other non-infectious causes of systemic inflammatory response syndrome in critically ill adult patients and should not be used as often as it is currently done in the critical care setting.

[edit] References

^ Meisner M, Tschaikowsky K, Palmaers T, Schmidt J. Comparison of procalcitonin (PCT) and C-reactive protein (CRP) plasma concentrations at different SOFA scores during the course of sepsis and MODS. Crit Care. 1999;3(1):45-50. PMID 11056723 Full Text
^ Balci C, Sungurtekin H, Gurses E, Sungurtekin U, Kaptanoglu B. Usefulness of procalcitonin for diagnosis of sepsis in the intensive care unit. Crit Care. 2003 Feb;7(1):85-90. Epub 2002 Oct 30. PMID 12617745 Full Text
^ Tang Benjamin; Eslick GD; Craig JC; McLean AS. Accuracy of procalcitonin for sepsis diagnosis in critically ill patients: systematic review and meta-analysis.Lancet Infect Dis. 2007 7(3) 210-7 PMID 17317602