According to this study, always – but rarely.
This is a prospective 3-center trauma study attempting to discern clinical variables that predicted the absence of serious traumatic chest injury in the setting of blunt trauma. 2,628 subjects enrolled, with 271 of them diagnosed with a serious injury – pneumothorax, hemothorax, great vessel injury, multiple rib fractures, sternal fracture, pulmonary contusion, and diaphragmatic rupture. They do a recursive partitioning analysis and identify a combination of seven clinical findings that had a 99.3% (97.4 – 99.8) sensitivity for serious traumatic injuries.
But, I might be missing the point of this instrument a little bit. Only 10% of their cohort had a traumatic injury – yet out of the remaining 90% without serious traumatic injury, their rule could only carve out 14% as low risk. These low risk patients, the authors then propose, obviates any chest imaging at all. While I am all for reducing unnecessary testing, this seems like an awfully low yield decision rule. Yes, this study identifies young patients who are perfectly fine after a low-risk blunt trauma and do not need even an x-ray – but I’d really rather see more work preventing some of the 584 chest CTs performed in this cohort. Additionally, their criterion standard for negative imaging is inadequate – most received CXR alone and there’s no follow-up protocol to test for possible missed injuries, whether clinically significant or not.
Considering the criteria they identified, it seems they could almost get equal or greater reduction in imaging if the clinicians were simply a little more thoughtful with respect to knee-jerk imaging in trauma.
“Derivation of a Decision Instrument for Selective Chest Radiography in Blunt Trauma.”
www.ncbi.nlm.nih.gov/pubmed/21045745