Investigations

Why?

A raised white cell count makes a 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 pulmonary embolism a (pre-test probability: 21%)	pulmonary embolism (v/q scan, angiography, autopsy)	white cell count > 10 x 109/l	1.7 (1.2 to 2.6)	31%	0.68 (0.47 to 0.98)	15%