Investigations

Why?

• It can help diagnose PE but not rule it out ^b
• It is a cost-effective method ^b

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: 21%)	pulmonary embolism (v/q scan, angiography, or autopsy)	abnormal impedence plethysmography	13 (3.7 to 44)	77%	0.74 (0.60 to 0.91)	16%