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Procalcitonin as the name suggests is a precursor of the hormone calcitonin

Coded by the CALC 1 gene on Chr 11,its a 116AA peptide

PrePCT >> PCT >> Calcitonin

Bact inf=IL6TNFaIL1b=Productn of PCT

Normal PCT in health <0.1ng/ml

In patients with bacterial infections PCT corelates with severity of infection

PCT starts to3-4hrs following an infection,
peaks at ~12 hrs post infection.

The image below beautifully summarizes the kinetic profile of biomarkers in bacterial infections

As seen CRP rises and peaks later and stays elevated for a longer time even after resolution of infection.

But there are other reasons for an PCT like major surgery, burns, severe trauma etc.
Cardiogenic shock also l/t PCT

That's where serial monitoring becomes important.
The levels wont stay elevated in these conditions.

Med Ca thyroid and SCLC l/t PCT(dysreg productn)

Similarly a Normal PCT doesn't r/o bact infection. Localized infections like empyema, osteomyelitis can have normal PCT.

PCT is quantified by immunoassay technique. The 1st commercial kit was BRAHMS PCT LIA.

PCT Kryptor an automated assay was FDA approved in 2008

Semiquantitative strip tests use immunochromatography and serve as point of care tests for PCT.

PCT guided antibiotic therapy was evaluated in the PRORATA trial and it was effective inantibiotic exposure.

However, PCT is not a good marker for intensifying antibiotics (PASS study data)

A combination of CRP and PCT may prove helpful in distinguishing bacterial vs IFI in patients with febrile neutropenia.
PCT and CRP should lead to a high suspicion of IFI in patients with neutropenia.

References :
http://dx.doi.org/10.1097/HS9.0000000000000170

Meisner M. Procalcitonin -Biochemistry and Clinical
Diagnosis. ISBN

PRORATA trial ; Lancet 2010

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