Investigations

• antinuclear antibodies ^c

Why?

A positive ANA test increases the chance of SLE

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: 9.8%)	Systemic Lupus Erythrematosis (American Rheumatology Association criteria for SLE)	ANA positive	6.9 (3.2 to 15)	43%	0.28 (0.084 to 0.93)	3%