Critically evaluate the role of Procalcitonin (PCT) as a biomarker in the diagnosis and management of sepsis.
• PCT is synthesized physiologically by thyroid C cells but in sepsis has extrathyroidal origin from the inflamed/infected tissue
• The biochemical and clinical profile well described
• It is easy to perform (Blood test), not too expensive and provides a quick answer in about 30 minutes. Blood cultures can take up to 24 hours.
• PCT is no gold standard for infection. There number of reports of PCT elevation in non-septic SIRS, immediately after surgery and trauma.
• Data from meta-analyisis are conflicting, some suggesting it is superior to CRP, whilst others have concluded it is a weak biomarker in critical illness.
• PCT is not elevated in viral infection, autoimmune disorders and immunocompromised patients – hence empiric therapy still the way in these patients.
• PCT does not tell you the site of infection/inflammation. History, clinical examination and other investigations like CT scan can.
• PCT is a biomarker and cannot replace good history taking, systematic clinical examination, appropriate investigations for the source of sepsis.
Few prospective randomised studies using,PCT as a guide to antibiotic therapy, have showed that prescription rate and the cost of antibiotics was reduced significantly with similar outcomes compared to the conventional approach
(Mention of the recent Lancet paper (Jan2010 – ProRata study and its conclusions is worthy of extra credit).
If one were to approach this in a structured fashion, the answer would resemble the following:
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