TOPLINE:

Performing chest x-ray as a first‑line test for clinically suspected community‑acquired pneumonia, independently of its result, reduced antibiotic initiation compared with no imaging, whereas C‑reactive protein (CRP) testing produced a smaller but still significant reduction.

METHODOLOGY:

• Researchers in France conducted a randomised trial among 3729 GPs (median age, 40 years) to determine whether providing chest x-ray and/or the CRP test reduced the rate of antibiotic initiation in patients with clinically suspected community‑acquired pneumonia.
• Each GP was presented with one of the three vignette scenarios — no chest x-ray, a normal chest x-ray, or a chest x-ray compatible with pneumonia — and was simultaneously shown a prespecified CRP value: negative (15 mg/dL) or positive (105 mg/dL).
• Scenarios also varied by patient comorbidities and clinical severity signs; GPs recorded antibiotic decisions before and after seeing the CRP value.
• The primary endpoint was the rate of antibiotic initiation when chest x‑ray was used as a first-line test, assessed both overall and by chest x-ray results.
• Secondary endpoints included the rate of antibiotic initiation when CRP was used as a first‑line test or as a reflex test after chest x-ray.

TAKEAWAY:

• Antibiotics were initiated in 90.2% of scenarios when chest x-ray was not performed vs 71.4% of scenarios when chest x-ray was performed, resulting in a 21% reduction in antibiotic initiation (relative risk [RR], 0.79; 95% CI, 0.77-0.82).
• When the chest x-ray was compatible with pneumonia, 98.7% of GPs initiated antibiotics; when the chest x-ray was normal, 44.2% of GPs initiated antibiotics.
• Among 1228 GPs assigned to CRP testing first, antibiotics were initiated in 76.3% with no chest x-ray vs 90.3% with no testing, resulting in a 15% reduction in antibiotic initiation (RR, 0.84; 95% CI, 0.81-0.87).
• In the analysis of 2444 GPs who received CRP as reflex testing after chest x-ray, a positive CRP value increased antibiotic initiation (RR, 1.83; 95% CI, 1.66-2.02), whereas a negative CRP value reduced it (RR, 0.54; 95% CI, 0.46-0.64).

IN PRACTICE:

"Combining these two tests, particularly using CRP point-of-care testing as a reflex testing in cases of persisting uncertainty after CXR [chest x-ray] or when CXR is unavailable, would help GPs in their decision to initiate antibiotics," the authors wrote.

SOURCE:

This study was led by Juliette Pinot, Université Paris Cité and Université Sorbonne Paris Nord, Paris, France. It was published online on March 14, 2026, in Clinical Microbiology and Infection.

LIMITATIONS: 

The study used an equal number of positive and negative chest x‑rays, which did not reflect real‑world rates. The researchers focused on very low or very high CRP levels, which may have led to an overestimation of the effect; intermediate CRP values (20-100 mg/dL) were not explored. Moreover, because CRP was added only after chest x‑ray, the study could not determine whether using CRP before imaging would have worked better.

DISCLOSURES:

This study was funded by the Collège National des Généralistes Enseignants. The authors reported having no competing interests.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.