UCLA Procalcitonin Summary
June 2016
Procalcitonin at UCLA
Daniel Z. Uslan, MD
Background
Up to 50% of antimicrobial use in the inpatient setting is unneeded or inappropriate.1For example, viruses
are typically the cause of acute bronchitis but despite this as much as 80% of patients will be prescribed
antibiotics.2 Also the length of treatment for most infections has been poorly studied and it is likely that
treatment durations are inappropriately long.3 The appropriate use of antimicrobials is essential because
they are associated with patient harm including drug toxicity, increased drug resistance, and collateral
damage such as Clostridium difficile-associated diarrhea.4-6Procalcitonin has been evaluated as a
biomarker to assist the clinician in the diagnosis and treatment of bacterial infection. Procalcitonin has
been studied most thoroughly for lower respiratory tract infections and sepsis and its use is associated
with decreased antimicrobial usage without worsening of clinical outcomes. 7-13
What is Procalcitonin?14-16
Procalcitonin (PCT) is a 116 amino acid precursor of calcitonin which under normal circumstances is
produced by the thyroid C-cells. Serum concentrations of PCT are normally <0.05 ng/mL but in
circumstances of systemic inflammation, particularly bacterial infection, PCT is produced in large
quantities by many body tissues. It is detectable within 2-4 hours and peaks within 6-24 hours (as
opposed to CRP which begins to rise after 12-24 hours and peaks at 48 hours). 14-16 PCT production is not
impaired by neutropenia or other immunosuppressive states. PCT levels parallel the severity of the
inflammatory insult or infection; those with more severe disease have higher PCT levels. Furthermore,
procalcitonin has some utility as a prognostic indicator with higher serum concentrations related to the
risk of mortality.
PCT has some advantages other biomarkers in common clinical use such as C-reactive protein (CRP)
and white blood cell count. The advantages of PCT over older markers include: specificity for bacterial
infection (verses inflammation in general), the rapidity of its rise after an insult (6 hours), the rapid decline
with immune control on infection (half-life of 24 hours), excellent correlation with severity of illness (higher
levels in more severely ill), and the lack of impact of anti-inflammatory and immunosuppressive states on
production.
What are clinical situations where PCT may be useful?
Differentiation of bacterial versus viral respiratory tract infection
Determination of antibiotic treatment length in respiratory infections
Diagnosis, risk stratification, and monitoring of sepsis and septic shock
Monitoring response to antibacterial therapy
Diagnosis of systemic secondary infection post-surgery, post-organ transplant, and in severe burns,
multiorgan failure, and severe trauma
Diagnosis of bacteremia and sepsis in adults and children (including neonates)
Differentiating bacterial versus viral meningitis
Diagnosis of renal involvement in pediatric urinary tract infections
