Although chest radiography (CXR) has traditionally been used as the initial diagnostic test, pulmonary ultrasound (US) has emerged in recent years as a radiation-free, portable, and potentially more sensitive and specific alternative.

To evaluate the diagnostic accuracy of US compared to CXR for detecting community-acquired pneumonia (CAP) in adults through a systematic review and meta-analysis.

Comprehensive searches were conducted in SCOPUS, Web of Science, PubMed, and EMBASE databases. Observational studies comparing US with CXR in diagnosing CAP were included, using computed tomography as the reference standard for all patients. Random-effect models were used for statistical analysis, calculating sensitivity, specificity, likelihood ratios (LR), and diagnostic odds ratios (DOR). Meta-regression analyses were performed, and SROC curves were constructed to compare diagnostic performance.

Eight studies using CT as a reference standard were included. US showed superior performance with sensitivity 90.0 % (95 % CI: 81.3-96.2 %), specificity 90.8 % (95 % CI: 79.9-97.7 %), LR+ 9.45 (95 % CI: 3.73-23.94), LR- 0.12 (95 % CI: 0.06-0.24), and DOR 79.74. CXR demonstrated lower values with sensitivity 72.6 % (95 % CI: 61.7–82.4 %), specificity 82.0 % (95 % CI: 65.5–93.9 %), LR+ 3.98 (95 % CI: 1.87-8.49), LR- 0.36 (95 % CI: 0.23-0.54), and DOR 11.17. Both modalities showed significant heterogeneity, which was not explained by the sample size in meta-regression.

Pulmonary US demonstrates substantially higher diagnostic accuracy than CXR for CAP detection, with particularly strong performance in excluding pneumonia as evidenced by its low negative LR. While CXR maintains relevance where US is unavailable or for evaluating specific thoracic conditions, implementing US can optimize pneumonia diagnosis and potentially reduce unnecessary antibiotic use, particularly in emergency and critical care settings.