From the Guidelines
Procalcitonin (PCT) levels should not be solely relied upon to distinguish between viral and bacterial etiologies of community-acquired pneumonia (CAP), as its sensitivity ranges from 38% to 91% and it cannot be used to justify withholding antibiotics from patients with CAP. The reported sensitivity of procalcitonin to detect bacterial infection is variable, underscoring the need for clinical judgment in conjunction with PCT levels 1. Some studies suggest that PCT levels of <0.1 mg/L indicate a high likelihood of viral infection, whereas levels >0.25 mg/L indicate a high likelihood of bacterial pneumonia, but these thresholds are not universally accepted 1.
Key Points to Consider
- PCT levels are not a reliable standalone test for diagnosing bacterial pneumonia, and clinical judgment should always be used in conjunction with PCT levels 1.
- The addition of procalcitonin concentrations to symptoms and signs does not add relevant additional diagnostic information for pneumonia 1.
- PCT levels can be influenced by various factors, including severe trauma, surgery, or certain inflammatory conditions, which can lead to false positives.
- Serial measurements of PCT levels can be useful in monitoring the response to antibiotic therapy, but this should be done in conjunction with clinical assessment and other laboratory markers.
Clinical Application
In clinical practice, PCT levels should be used as an adjunct to clinical judgment, rather than a replacement for it. A strong recommendation from the American Thoracic Society and Infectious Diseases Society of America is to initiate empiric antibiotic therapy in adults with clinically suspected and radiographically confirmed CAP, regardless of initial serum procalcitonin level 1. This approach prioritizes the potential benefits of early antibiotic treatment over the potential risks of unnecessary antibiotic use.
From the Research
Procalcitonin and Pneumonia
- Procalcitonin is a biomarker that has been proposed to guide antibiotic therapy in patients with community-acquired pneumonia (CAP) 2.
- The sensitivity and specificity of serum procalcitonin levels in distinguishing bacterial pneumonia from viral pneumonia have been reported to be 0.55 and 0.76, respectively 2.
- A study found that procalcitonin levels were significantly higher in patients with typical pneumonia compared to those with atypical pneumonia, with median levels of 7.64 ng/ml and 0.80 ng/ml, respectively 3.
Procalcitonin Levels
- Elevated procalcitonin levels have been associated with bacterial infections, and a cutoff value of 0.1 ng/ml has been suggested for differentiating between acute exacerbation and bacterial pneumonia in patients with interstitial lung disease 4.
- Procalcitonin levels have been reported to be useful in predicting the course and prognosis of pneumonia, with higher levels indicating a more severe infection 5.
- However, procalcitonin levels can be increased in noninfectious conditions and may remain low in localized bacterial infections, highlighting the importance of follow-up measurements 5.
Sensitivity and Specificity
- The sensitivity and specificity of procalcitonin levels in diagnosing bacterial pneumonia have been reported to be 88.9% and 100%, respectively, at a cutoff value of 0.1 ng/ml 4.
- However, the sensitivity and specificity of procalcitonin levels can vary depending on the population and the specific clinical context, and should be interpreted in conjunction with other clinical and laboratory findings 2, 3, 4, 5.