From the Guidelines
Procalcitonin is a biomarker protein that increases in the bloodstream during bacterial infections, and its levels can guide antibiotic therapy decisions, with levels below 0.1 ng/mL suggesting bacterial infection is unlikely, and levels above 2.0 ng/mL strongly suggesting sepsis or severe bacterial infection. When interpreting procalcitonin results, it is essential to consider the clinical context and other laboratory findings, as certain conditions like trauma, surgery, and some cancers can cause non-infectious elevations 1. Procalcitonin is particularly useful for distinguishing between bacterial and viral infections, as viral infections typically do not significantly elevate procalcitonin levels. According to a recent systematic review and meta-analysis, procalcitonin has a higher diagnostic accuracy and specificity than C-reactive protein (CRP) for diagnosing sepsis in adult patients 1.
Key Points to Consider
- Normal procalcitonin levels are typically less than 0.1 ng/mL in healthy individuals 1
- Levels between 0.1-0.5 ng/mL represent a low risk of severe bacterial infection
- Levels between 0.5-2.0 ng/mL indicate a moderate risk of sepsis
- Levels above 2.0 ng/mL strongly suggest sepsis or severe bacterial infection
- Procalcitonin can guide antibiotic therapy decisions, with rising levels suggesting worsening infection and falling levels indicating response to treatment 1
- Serial measurements are more valuable than single readings, as they help track infection progression or resolution
Clinical Application
Procalcitonin should be interpreted alongside clinical assessment and other laboratory findings, as its utility stems from its rapid increase within 2-4 hours of bacterial infection onset, with levels correlating with infection severity and bacterial load 1. Measuring procalcitonin or CRP in critically ill patients with a new fever and no clear focus of infection with low to intermediate clinical probability of bacterial infection is recommended in addition to bedside clinical evaluation, but not in patients with high clinical probability of bacterial infection 1. A meta-analysis of 11 RCTs involving 4,482 patients reported that procalcitonin-guided antibiotic treatment in ICU patients with infection and sepsis patients resulted in improved survival and lower antibiotic treatment duration 1.
From the Research
Definition and Role of Procalcitonin
- Procalcitonin (PCT) is a biomarker that has been rediscovered for its role in the diagnosis and management of sepsis 2.
- It is a member of the calcitonin superfamily and is synthesized by various tissues and organs in response to bacterial infections 3, 4.
- PCT has demonstrated superior diagnostic accuracy for bacterial infections, including sepsis, compared to traditional biomarkers such as C-reactive protein and white blood cell count 2, 5.
Interpretation of Procalcitonin Levels
- Elevated PCT levels can indicate bacterial infection, but may also be increased in non-infectious disease conditions 2, 3.
- The interpretation of PCT levels must be done in the context of medical history, physical examination, and microbiological assessment 5.
- PCT levels can be used to guide antimicrobial therapy, monitor response to treatment, and diagnose secondary infections 2, 3, 4.
- In pediatric patients, PCT can be used as a biomarker for sepsis, but its measurement has challenges and limitations 6.
Clinical Utility of Procalcitonin
- PCT can be used to distinguish between bacterial and viral infections, although it may not be effective in all cases 3.
- It can be used to guide antibiotic therapy, reduce unnecessary antimicrobial use, and improve patient outcomes 2, 4.
- PCT has been shown to be a helpful biomarker for early diagnosis of sepsis in critically ill patients, with a mean sensitivity of 0.77 and specificity of 0.79 5.