From the Guidelines
Procalcitonin (PCT) has moderate to good clinical utility in guiding antibiotic therapy decisions, with sensitivity ranging from 70-85% and specificity between 75-85% for bacterial infections, as supported by the most recent evidence from 2023 1.
Clinical Utility of Procalcitonin
The clinical utility of PCT is most valuable when used as part of a comprehensive clinical assessment rather than as a standalone test. For respiratory infections, a PCT level <0.25 μg/L suggests viral etiology where antibiotics can likely be withheld, while levels >0.5 μg/L more strongly indicate bacterial infection warranting antibiotic therapy.
Sensitivity and Specificity
PCT's sensitivity and specificity are crucial in guiding antibiotic therapy, with the most recent study indicating that PCT has a sensitivity of 0.80 (95% CI, 0.69–0.87) and a specificity of 0.77 (95% CI, 0.60–0.88) for diagnosing sepsis 1.
Serial Measurements
Serial PCT measurements are particularly useful, with a decline of >80% from peak or levels falling below 0.5 μg/L indicating appropriate response and supporting antibiotic discontinuation, as demonstrated by the Stop Antibiotics on Procalcitonin Guidance Study 1.
Limitations
PCT has limitations including false positives in conditions like trauma, surgery, and certain cancers, and false negatives in localized infections or when measured very early in disease course.
Clinical Application
PCT should always be interpreted alongside clinical presentation, other laboratory findings, and patient-specific factors rather than used as the sole determinant for antibiotic decisions, as recommended by the Society of Critical Care Medicine and the Infectious Diseases Society of America guidelines 1. Some key points to consider when using PCT in clinical practice include:
- PCT levels can be used to support the discontinuation of empiric antibiotics in patients who initially appeared to have sepsis, but subsequently have limited clinical evidence of infection, as suggested by the Surviving Sepsis Campaign guidelines 1.
- PCT-guided antibiotic treatment in ICU patients with infection and sepsis patients has been shown to result in improved survival and lower antibiotic treatment duration, according to a meta-analysis of 11 RCTs involving 4,482 patients 1.
- The largest systematic review and meta-analysis to date of 16 studies and greater than 5000 patients showed that PCT-guided antibiotic discontinuation appeared to decrease antibiotic utilization by 1 day and improve mortality, although the evidence was of low certainty 1.
From the Research
Clinical Utility of Procalcitonin
- Procalcitonin (procal) is a biomarker that can help guide antibiotic therapy by distinguishing between bacterial and non-bacterial infections 2, 3, 4, 5, 6.
- The clinical utility of procalcitonin lies in its ability to reduce antibiotic use and exposure, thereby decreasing the risk of side effects and controlling emerging bacterial multi-resistance 2, 4, 5.
Sensitivity and Specificity
- Procalcitonin levels of <0.25 µg/L can guide the decision to withhold antibiotics or stop therapy early in stable, low-risk patients with respiratory infections 2, 3.
- In critically ill patients with suspected sepsis, procalcitonin levels of <0.5 µg/L or levels that decrease by ≥80% from peak can guide discontinuation of antibiotics once patients stabilize 2, 3.
- A cutoff value of 0.25 μg/L in non-ICU patients or of 0.5 μg/L in ICU patients seems appropriate for making a decision about the initiation and discontinuation of antibiotic therapy 3.
Guiding Antibiotic Therapy
- Procalcitonin-guided antibiotic stewardship protocols have shown appreciable reductions in antibiotic use and duration of therapy in respiratory infections, sepsis, and other infections, with positive effects on clinical outcomes 4, 5.
- Patient-specific decisions regarding antibiotic usage are highly complex and require consideration of the clinical situation, acuity and severity of presentation, as well as procalcitonin test results 5.
- Low procalcitonin levels can help rule out bacterial infection in patients with both low pretest probability for bacterial infection and low-risk general condition, while high-risk individuals and/or high pretest probability for infection require empiric antibiotic treatment 5.