Investigations

• carcinoembryonic antigen (CEA) ^c

Why?

High levels of carcinoembryonic antigen can diagnose malignancy

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
pleural effusion c (pre-test probability: 31%)	malignancy (histology or cytology)	CEA > 40 ng/ml	infinity (21 to infinity)	100%	0.57 (0.46 to 0.70)	21%
pleural effusion c (pre-test probability: 34%)	malignancy (histology or cytology)	CEA > 10 ng/ml	5.0 (3.0 to 8.2)	72%	0.59 (0.49 to 0.72)	23%