The measurement of procalcitonin has been suggested to be useful in the diagnosis of bacterial sepsis in both adults and neonates, however as stated by the National Institute for Health and Care Excellence (NICE guideline NG51), the evidence for its use as a diagnostic biomarker is lacking and requires further large scale randomised controlled trials to justify its use in these settings.
Procalcitonin has a more established role in antibiotic stewardship and that is the main purpose for which this test was introduced at South Tees Hospitals NHS Foundation Trust. In this situation the test is ordered at the request of a consultant intensivist or microbiologist which can help to guide antimicrobial therapy for patients mainly within critical care. More recently the use of procalcitonin has been expanded to help guide antimicrobial therapy for patients with COVID-19.
Procalcitonin was described as sepsis-associated protein in 1993. It shares a common structure with pro-hormone of calcitonin which is produced by the C-cells of thyroid and undergoes proteolysis to produce calcitonin. In response to bacterial infection, adhering monocytes also produce procalcitonin (independently of the thyroid C-cells) which initially acts as a chemokine, recruiting additional monocytes. The adhesion of these to parenchymal cells induces these tissues to also more procalcitonin, which modulates the immune response, inducing pro-inflammatory cytokines and altering vasodilation. Experimentally it has been demonstrated that neutralisation of PCT in bacterially shocked hamsters increases survival, while administration of PCT increases mortality. The effects of procalcitonin may be advantageous in local infection, but become deleterious in systemic infection with higher levels of procalcitonin being associated with severe systemic infections such as severe sepsis. However, although there is an association between high procalcitonin concentration and sepsis, such concentrations have also been reported in patients with other severe injuries such as trauma and burns.
No reference range is currently reported; for guiding microbial therapy an algorithm is used within critical care for the interpretation of procalcitonin concentrations.
Serum (SST yellow top tube) specimen
Within 2 hours