Procalcitonin: What is its value clinically?

Introduction

This week at work we had a patient that presented to the ICU from an outside hospital. The patient had an anaphylactic reaction that caused the upper airway to be compromised. The team at the outside hospital tried to intubate the patient, but was unsuccessful. The patient required an emergency tracheotomy, and was subsequently transferred to a tertiary facility. During my rounds, I noticed that the Procalcitonin (PCT) level on admission was 7.1. Not being familiar with PCT, I decided to investigate what Procalcitonin was, how useful the biomarker is clinically, and how it is used to help guide care for the patient. In other words, I wanted to answer the question; what is the utility of Procalcitonin, clinically? Here’s what I found out.

Procalcitonin is a prohormone precursor of calcitonin that is expressed mainly in C cells of the thyroid gland. The conversion of Procalcitonin is inhibited by different cytokines and bacterial endotoxins. The main utility of Procalcitonin is to establish the presence of bacterial infections, because serum Procalcitonin levels rise and fall sharply in bacterial infections. In a healthy person, PCT levels are typically very low.

When is PCT of any value?

Procalcitonin has some limitations and its utility is variable, depending on the setting and age population. However, Procalcitonin can be reliable used to guide antibiotic therapy and has been shown to reduce morbidity and mortality Procalcitonin levels can be useful in the following:

-       adult ICU patient’s to help guide discontinuance of antibiotics

-       once PCT levels have dropped to 0.5-1 ng/mL, it is generally accepted to stop antibiotic coverage

-       PCT levels are also helpful in determining when to give antibiotics. For example, PCT levels are particularly helpful in patients with respiratory tract infections such as: COPD, community acquired pneumonia, bronchitis, URI/LRI infections ----> start antibiotics if PCT > 0.25-0.5 ng/mL

When is PCT of no value?

-       Viral infections

-       The use of PCT levels should not be used for intensification of antibiotics in adult ICU patients, because this was associated with an increase in mortality

-       Currently there is insufficient evidence to support the use of Procalcitonin-guided antibiotic therapy in neonates with sepsis, children with unknown source of fever, or in the post-operative, at risk for infection population.

Therefore, Procalcitonin is just another tool in a clinician’s kit that can be used to help in making a diagnosis and guiding treatment, but like so many other indices and biomarkers, it is not the Holy Grail.

Reference:
1. Soni, NJ., Samson, DJ., Galaydick, JL., Vats, V., Huang, ES., Aronson, N., Pitrak, DL. Procalcitonin-Guided Antibiotic Therapy: A Systematic Review and Meta-analysis. J. of Hosp Med; Vol. 8, No. 9, 2013; 530-540.
2. Prkno, A., Wacker, C., Brunkhorst, FM., Schlattmann, P. Procalcitonoin-guided therapy in intensive care unit patients with severe sepsis and septic shock - a systematic review and mata-nalysis. Crit. Care 2013, 17R291
3. Morris, C., Paul, K. Procalcitonin-Guided Antibiotic Therapy for Acute Respiratory Infections. American Family Physician, Vol 94, No. 1, July 1, 2016; 57-58.