Investigations

• mast cell tryptase (within 6 hrs of the episode) ^d

• skin prick testing ^d
• IgE levels ^d
• Intradermal testing for drug induced episodes ^d

Why?

Mast cell tryptase can rule out anaphylaxis and intradermal testing can help rule it in

Patient	Target Disorder and Reference Standard	Diagnostic Test	LR+ (95% CI)	Post-test Probability	LR- (95% CI)	Post-test Probability
suspected anaphylaxis d (pre-test probability: 64%)	Drug-induced anaphylaxis (sole agent, positive passive transfer or subsequent anaesthesia)	intradermal testing	22 (3.2 to 150)	98%	0.24 (0.17 to 0.35)	30%
suspected anaphylaxis d (pre-test probability: 39%)	Problematic subsequent general anaesthetic	skin-prick or intradermal testing	1.2 (1.1 to 1.4)	44%	0.18 (0.04 to 0.76)	11%
suspected anaphylaxis d (pre-test probability: 44%)	Anaphylaxis (radioimmunoassay or intradermal testing)	Mast cell tryptase >3mcg/L	4.9 (3.6 to 6.6)	79%	0.066 (0.032 to 0.14)	5%