Investigations

• amylase ^c

Note:

• An fluid amylase >100 U/l is uncommon in patients undergoing thoracentesis. ^c

Why?

An raised amylase makes an exudate more likely.

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: 49%)	exudate (final diagnosis)	amylase 1000 U/l or more	8.5 (2.0 to 35)	89%	0.80 (0.70 to 0.91)	43%