Written by Clay Smith
CXR was a poor screening test for acute aortic syndrome. If you suspect this diagnosis, just get a CTA.
Why does this matter?
Guidelines recommend CXR to screen for acute aortic syndromes in low pretest probability patients. As a review, the findings of acute aortic syndrome on CXR are: “poor definition or irregularity of the aortic contour, double aortic knob sign, inward displacement of aortic wall calcification by more than 10 mm, tracheal displacement to the right, displacement of a nasogastric tube, left sided pleural effusion, suspected pericardial effusion, left apical opacity,” and mediastinal enlargement (ME), “defined as a maximum width of mediastinum ≥80 mm at the level of the aortic knob or a ratio of mediastinum to chest width >0.25 or ME based on subjective evaluation.” How does CXR actually perform as a screening test?
Not the way to screen for this problem
This was a secondary analysis of ADviSED. Use of an aortic dissection detection risk score plus mediastinal enlargement on CXR had sensitivity of 67%, specificity 83%. The risk score plus any sign on CXR had sensitivity 69%, specificity 77%. For CXR alone, without the risk score, sensitivity was 54%, specificity 92% for mediastinal enlargement; sensitivity 60%, specificity 85% for any sign on CXR. Inter-rater agreement between radiologists for mediastinal enlargement was fair to moderate (k = 0.44). What this all means is that a CXR is a poor screening tool for acute aortic syndromes. If mediastinal enlargement or other signs are seen on CXR, this is concerning and needs further workup. If you suspect acute aortic syndrome, it’s best to just get a CTA.
Integrated use of conventional chest radiography cannot rule out acute aortic syndromes in emergency department patients at low clinical probability. Acad Emerg Med. 2019 Jun 20. doi: 10.1111/acem.13819. [Epub ahead of print]
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Reviewed by Thomas Davis