Procalcitonin Is Useful for Evaluating Patients with Ambiguous Presentation and for Early Discontinuation of Antibiotics in Community-acquired Pneumonia.

To the Editor:

The updated American Thoracic Society and Infectious Diseases Society of America guidelines for the diagnosis and treatment of adults with community-acquired pneumonia (CAP) conclude that procalcitonin (PCT) is not recommended to determine the need for initial antibacterial therapy in patients with clinically suspected and radiographically confirmed CAP (1). It seems rational that in a patient with a high pretest probability for pneumonia, any biomarker (including PCT) that is not 100% accurate should not have a strong influence on treatment decisions. The advantage of using PCT for the management of patients with CAP, however, has been demonstrated for patients in whom a CAP diagnosis is unclear (e.g., patients with no infiltrate in chest X-ray) and for monitoring patients with CAP to decide whether to stop treatment early. Most trials that evaluated PCT for the management of CAP did not rely on the initial PCT level and instead focused on the kinetics of this blood marker to indicate that antibiotic treatment should be stopped early. The initial PCT level was found to be helpful in patients with a bronchitis-like illness and possible CAP but an ambiguous clinical presentation (2, 3). A recent meta-analysis of individual patient data that focused specifically on patients with respiratory infection and CAP who had participated in randomized trials showed that PCT is highly effective in reducing the duration of antibiotic treatment (4, 5). Specifically, the analysis included 6,708 patients from 26 eligible trials in 12 countries and found a 2.4-day reduction in antibiotic exposure (5.7 vs. 8.1 d [95% confidence interval (CI), –2.71 to –2.15]; P < 0.0001) and a reduction in antibiotic-related side effects (16% vs. 22%, adjusted odds ratio, 0.68 [95% CI, 0.57 to 0.82]; P < 0.0001). Importantly, when PCT was used to guide discontinuation of treatment, patients had significantly improved clinical outcomes (odds ratio for mortality, 0.83 [95% CI, 0.70–0.99]; P = 0.037).

Thus, there is strong clinical evidence that PCT is useful for evaluating patients with lower respiratory infection and ambiguous presentation and for stopping antibiotics early in patients with confirmed CAP. It is unfortunate that the updated guideline (1) focused on a clinical situation in which no biomarker would be expected to have a strong influence on treatment (i.e., patients with clinically suspected and radiographically confirmed CAP) and unfortunate that it did not include recommendations for using PCT in ambiguous clinical situations and for guiding treatment duration, both of which have a strong impact on antibiotic overuse and associated health risks.