Background The postmortem diagnosis of anaphylaxis remains difficult due to the lack of specific biomarkers. Mast cell tryptase (MCT) levels are used as a marker of mast cell degranulation in living patients and elevated levels have also been described in postmortem serum samples in anaphylaxis-associated deaths, although elevated levels may also be seen in non-anaphylaxis-associated deaths.

Objective To investigate the effects of cause of death, site of blood sampling, degree of sample haemolysis and the presence of opiates on postmortem MCT levels.

Method We obtained sera from three collection sites from 189 non-suspicious coronial postmortems and aortic samples from 10 anaphylactic deaths to characterise postmortem MCT.

Results MCT were elevated (>11.4 μg/L) in 57% of aortic samples, 58% of femoral samples and 30% of subclavian samples. In aortic samples, there were significantly higher levels of MCT in anaphylaxis-associated deaths compared with other causes of death. Aortic MCT levels >110 μg/L had a sensitivity of 80% and specificity of 92.1% for anaphylaxis-associated deaths. There was a significant correlation between MCT and degree of sample haemolysis but no correlation with the presence of opiates.

Conclusions Moderately elevated MCT levels are common in postmortem sera. Aortic values >110 μg/L may support a diagnosis of anaphylaxis-associated death, although the diagnosis should not be based on this test alone. There was significant variation between sample sites and reference ranges for individual sample sites should be established.