Anaphylaxis: a normal mast cell tryptase may help exclude it

Clinical bottom line (level 4)

  1. 40% of patients with suspected anaphylaxis during anaesthesia had it.
  2. A raised mast cell tryptase made anaphylaxis more likely (LR+4.9) , and a normal mast cell tryptase made anaphylaxis much less likely (LR-0.066) .
Fisher and Baldo: British Journal of Anaesthesia 1998; 80: 26-29
Expires November 2004

The study

Setting: operating theatres, Australia

350 patients (aged ?, ?% male) with possible anaphylactic reactions during anaesthesia

Independent unblinded reference standard, applied in some patients from a non-consecutive appropriate spectrum.
Reference standard:
  • intradermal testing and/or radioimmunoassay
Diagnostic test: mast cell tryptase taken within 1 to 6 hours of suspected reaction: increased if > 3 microgram/l or > 5 microgram/l post-mortem

The evidence

pre-test probability of anaphylaxis: 44%, (95% CI: 38% to 50%)

diagnostic test anaphylaxis no anaphylaxis LR+
(95% CI)		 post-test probability LR-
(95% CI)		 post-test probability
mast cell tryptase 125 33 4.9
(3.6 to 6.6) 		79% 0.066
(0.032 to 0.14) 		5%
total 132 169

Comments

  1. The reference standard was poorly defined - it is unclear which patients were judged to have had an anaphylactic reaction.

Citation

  1. Fisher MM, and Baldo BA: mast cell tryptase in anaesthetic anaphylactoid reactions. British Journal of Anaesthesia 1998; 80: 26-29
Contributor: Mike Bennett and Chris Ball, November 1999
Reviewer: Chris Ball

Clinical Question.
Patient suspected anaphylaxis
Intervention or Exposure mast cell tryptase
Outcome anaphylaxis