Validation of international consensus equation for acute serum total tryptase in mast cell activation: A perioperative perspective

Abstract

There is no standardized method for assessing serum total mast cell tryptase (MCT) in anaphylaxis. The consensus equation (peak MCT should be>1.2× baseline tryptase+2 mg/L) has been proposed to interpret acute MCT in mast cell activation syndrome (MCAS). To validate consensus equation in a perioperative setting analyses of cases of suspected perioperative anaphylaxis during general anaesthesia (GA) were performed. Anaphylaxis was defined as per World Allergy Organisation (WAO) criteria. Timed serial MCT measurements were mapped against the consensus equation and receiver operating characteristic (ROC) curves produced. A total of 82 patients (60 females, mean age 56.5 years±SD17.2) underwent investigation. Sixty (73%) patients fulfilled WAO criteria for anaphylaxis, and 22 patients did not. Aetiology included 59% IgE-mediated anaphylaxis, 2% non-IgE-mediated anaphylaxis, 12% anaphylaxis of unknown cause and 27% deemed non-anaphylaxis. IgE-mediated anaphylaxis included the following: NMBA (35%), antibiotics (46%), chlorhexidine (8%), patent blue dye (8%) and others (8%). An acute MCT with a comparable baseline was available in 71 of 82 (87%) patients (60 anaphylaxis and 11 controls). The median interquartile range (IQR) time from reaction to peak MCT was 1.34 (0.82-2.51) hours. Analyses confirmed that a rise in acute MCT greater than that defined by the equation had a sensitivity, specificity, positive predictive value (PPV) and negative (N) PV of 78%, 91%, 98% and 44%, respectively. The magnitude of increase in acute MCT above the threshold predicted by consensus equation was higher in the anaphylaxis group compared to controls (P=.0001). This equation has a high specificity, PPV with a moderate NPV and sensitivity in perioperative anaphylaxis.

Keywords: anaphylaxis; drug allergy; mast cells; tryptase.