Investigations

Look for any abnormality particularly: 

• atelectasis or pulmonary parenchymal abnormality
• pleural effusion 
• pleural-based opacity 
• decreased pulmonary vasculature 
• pulmonary oedema 

Why?

An abnormal chest X-ray makes pulmonary embolism slightly more likely

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected PE a (pre-test probability: 21%)	pulmonary embolism (angiography, follow-up)	abnormal chest X-ray	1.3 (1.1 to 1.4)	37%	0.48 (0.31 to 0.75)	18%
		atelectasis or parenchymal abnormality	1.4 (1.2 to 1.7)	40%	0.62 (0.47 to 0.83)	23%
		pleural effusion	1.5 (1.2 to 2.0)	42%	0.76 (0.62 to 0.92)	26%
		pleural-based opacity	1.6 (1.2 to 2.3)	44%	0.83 (0.71 to 0.96)	28%
		decreased pulmonary vasculature	1.8 (1.1 to 2.9)	45%	0.89 (0.81 to 0.99)	30%
		pulmonary oedema	0.34 (0.14 to 0.86)	14%	1.1 (1.1 to 1.2)