Evidence-based On-call

Pulmonary embolism

Investigations

Bilateral compression ultrasound ^a

of the common femoral, popliteal and distal popliteal veins - The test is positive if any vein is not fully compressible.

Why?

Compression ultrasound can help diagnose PE but not rule it out

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected pulmonary embolism ^a (pre-test probability: 17%)	pulmonary embolism (v/q scan, angiography)	positive ultrasound scan	10 (4.2 to 25)	90%	0.73 (0.66 to 0.81)	13%