Response: Re: Signs and Symptoms That Rule Out Community-Acquired Pneumonia in Outpatient Adults: A Systematic Review and Meta-Analysis

To the Editor: We thank Dr. Kazal for the comment on our publication “Signs and Symptoms That Rule out Community-Acquired Pneumonia in Outpatient Adults: A Systematic Review and Meta-Analysis.”¹ Not only is lung ultrasonography a possible alternative to chest radiography (CXR) for the diagnosis of community-acquired pneumonia (CAP)^2,3 but also they can be useful for the differential diagnosis of chest pain and dyspnea in the emergency department.^4,5 We agree that point-of-care ultrasound (POCUS) should be explored in future studies on clinical decision rules for CAP, in addition to other point-of-care (POC) tests such as c-reactive protein.

However, POCUS is not yet ubiquitous nor has it replaced CXR as the current reference standard for diagnosing CAP. We express caution about the broad use of POCUS, as it suffers from subjective interpretation where interrater reliability varies⁶ and should be limited to clinicians with sufficient training and adequate patient volume.⁷ Most previous studies have been done in the emergency department or inpatient settings where there is a higher volume; whether primary care clinicians can duplicate that accuracy with lower volume requires further study. In addition, because pneumonia is relatively rare in primary care patients (about 3% to 4% of patients with lower respiratory tract symptoms), even a fairly accurate test can have a poor positive predictive value, leading to antibiotic overuse. We, therefore, advocate that future studies focus on the integration of simple heuristics, the overall clinical impression,⁸ validated clinical decision rules, and validated POC tests (eg, c-reactive protein)⁹ to identify patients at very low risk of CAP in the outpatient setting, as well as those who may benefit for further diagnostic testing, whether it be CXR or POCUS.