Critically evaluate the role of Procalcitonin (PCT) as a biomarker in the diagnosis and management of sepsis.
Answer and interpretation
- 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
- 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 shown 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