Investigations

• chest X-ray ^a looking for 
  • widening of the ^b aorta (particularly the aortic knob) or mediastinum
  • pleural effusion ^b
  • tracheal shift ^b

Why?

An abnormal chest X-ray makes aortic dissection more likely

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected aortic dissection b (pre-test probability: 1%)	aortic dissection (angiography)	radiologist's conclusion of the chest X-ray	7.3	7.3%	0.21	0.21%

Note:

• Radiologists guess at most features on a CXR for a patient with suspected aortic dissection ^b

Radiologists agree most often about widening of the aorta or mediastinum

Radiological feature b	K interobserver
widening of aortic knob	0.33
widening of mediastinum	0.28
widening of descending aorta	0.28
pleural effusion	0.27
tracheal shift	0.27
widening of ascending aorta	0.26