Investigations

• cardiomegaly ^b
• interstitial oedema ^b
• inverted pulmonary blood-flow distribution ^b

Why?

Cardiomegaly, interstitial oedema and venous congestion make heart failure slightly more likely

Patient b	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
dyspnoea and suspected left ventricular dysfunction (pre-test probability: 31%)	increased preload (?echocardiogram)	cardiomegaly	4	64%	0.7	24%
		redistribution/ congestion	2	47%	0.52	19%
		interstitial oedema	2	47%	0.7	22%
	decreased ejection fraction (?echocardiogram)	cardiomegaly	2.4	52%	0.62	21%
		redistribution/ congestion	3	57%	0.6	21%
		interstitial oedema	4	64%	0.9	29%