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Procalcitonin (PCT) is an FDA-approved test for use in guiding clinical decisions on starting, continuing, or stopping antibiotics in patients with lower respiratory tract infections, such as community-acquired pneumonia. Procalcitonin is also approved for use in determining whether to stop antibiotics.
Most of the small studies testing procalcitonin-driven algorithms have shown the method to be generally safe and effective at reducing antibiotic use. But a new study suggests that in patients with COPD exacerbations admitted to the ICU, withholding or stopping antibiotics based on PCT levels could be harmful.
Authors randomized 302 patients with COPD exacerbations admitted to French ICUs to have antibiotic decisions guided by procalcitonin, or clinical judgment without PCT. About 40% of the patients in each arm also had pneumonia diagnoses. Treating teams were encouraged to stop antibiotics for patients with normal PCT levels (<0.1 µg/L).
Three-month mortality was nominally higher in the PCT-guided group (20% vs 14%), not statistically significant. However, among the ~40% of patients who had not been prescribed antibiotics at the time of enrollment, and were randomized to PCT-driven antibiotic decisions, mortality was 31%, compared to 12% in the control group (more of whom got antibiotics). This was a pre-specified analysis.
Bacteria are known to frequently contribute to the pathology of COPD exacerbations, even in the absence of pneumonia (i.e., in patients with clear chest radiographs). Patients with severe COPD have altered microbiota of their respiratory tract, often with potentially pathogenic bacteria (Klebsiella, et al) living in a delicate balance with non-pathogenic bacteria. Exacerbations have been theorized to be triggered or worsened by a perturbation of this abnormal-but-stable bacterial ecology. Antibiotics often help reduce the severity or duration of exacerbations, especially in severe AECOPD.
Macrolide antibiotics such as azithromycin are also believed to have beneficial anti-inflammatory and immune modulating properties, independent of its antibacterial effects.
In fact, giving antibiotics indiscriminately (i.e., to all patients coming into an ICU) is known to reduce mortality from ventilator-associated pneumonia and also to reduce bacteremias. This kind of anti-stewardship approach is the only intervention that has been clearly shown to reduce mortality from VAP.
Procalcitonin shouldn't be used as a reason to withhold antibiotics from seriously ill patients with acute exacerbations of COPD, sepsis, or any other potential bacterial infection -- especially early in their clinical course.
Source: Intensive Care Medicine