Investigations

Note:

• Arterial blood gases are unhelpful in diagnosing or excluding PE, ^a but can help rule out other conditions. ^a

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: 36%)	pulmonary embolism (angiography)	pO2 80 mmHg or more (10.2 kPa)	1.1 (0.98 to 1.1)	37%	0.82 (0.61 to 1.1)	32%
		pCO2 35 mmHg or more (4.5 kPa)	1.0 (0.89 to 1.2)	37%	0.97 (0.83 to 1.1)	35%