What is the clinical significance of chest CT when the chest x-ray result is normal in patients with blunt trauma?

Background Computed tomography (CT) has been shown to detect more injuries than plain radiography in patients with blunt trauma, but it is unclear whether these injuries are clinically significant. Study Objectives This study aimed to determine the proportion of patients with normal chest x-ray (CXR) result and injury seen on CT and abnormal initial CXR result and no injury on CT and to characterize the clinical significance of injuries seen on CT as determined by a trauma expert panel. Methods Patients with blunt trauma older than 14 years who received emergency department chest imaging as part of their evaluation at 2 urban level I trauma centers were enrolled. An expert trauma panel a priori classified thoracic injuries and subsequent interventions as major, minor, or no clinical significance. Results Of 3639 participants, 2848 (78.3%) had CXR alone and 791 (21.7%) had CXR and chest CT. Of 589 patients who had chest CT after a normal CXR result, 483 (82.0% [95% confidence interval [CI], 78.7-84.9%]) had normal CT results, and 106 (18.0% [95% CI, 15.1%-21.3%]) had CTs diagnosing injuries - primarily rib fractures, pulmonary contusion, and incidental pneumothorax. Twelve patients had injuries classified as clinically major (2.0% [95% CI, 1.2%-3.5%]), 78 were clinically minor (13.2% [95% CI, 10.7%-16.2%]), and 16 were clinically insignificant (2.7% (95% CI, 1.7%-4.4%]). Of 202 patients with CXRs suggesting injury, 177 (87.6% [95% CI, 82.4%-91.5%]) had chest CTs confirming injury and 25 (12.4% [95% CI, 8.5%-17.6%]) had no injury on CT. Conclusion Chest CT after a normal CXR result in patients with blunt trauma detects injuries, but most do not lead to changes in patient management.