Anaesthetic hypersensitivity reactions can be IgE- or not IgE-mediated and are a challenge to find the causal agent. Histamine and tryptase determination are classically considered useful in the diagnosis of these reactions. The aim of our study was to assess the diagnostic usefulness of plasma histamine and different cut-off points of serum tryptase.
Patients suffering a reaction suggestive of hypersensitivity during general anaesthesia in Clínica Universidad de Navarra (2008–2012) were included. Serum tryptase and plasma histamine were measured at the time of the reaction and 2 h later. Baseline tryptase was also determined. Four to eight weeks after the reaction an allergological study was performed to all the drugs or products involved in the reaction.
Sixty-five patients suffered an immediate hypersensitivity reaction during the period of the study. Thirty-seven patients (20 male) with median age 48 years (12–79) were included because they completed allergological study, and histamine and tryptase were correctly obtained. Elevated plasma histamine was observed in 34 cases (92%). Tryptase exceeded twice the basal values in 10 patients (31%). Using different cut-off points of tryptase, the number of patients with elevated tryptase would be 15 patients (41%) for a cut-off point of 5 μg/L; 12 patients (32%) for a cut-off point of 8.23 μg/L; nine patients (24%) for 10.5 μg/L; and eight patients (22%) for 11.4 μg/L. The median tryptase level for the IgE-mediated reactions was 9.0 μg/L (2–70 μg/L) and 4.0 μg/L (3–13 μg/L) in non-IgE-mediated reactions (P < 0.01). Median tryptase levels were higher in more severe reactions (grade 2 or 3) in comparison with grade 1. The best ratio for serum-tryptase-during-reaction/basal-serum-tryptase to discriminate between IgE and non-IgE reactions was 2.0.
The best criterion for discriminating IgE- and non IgE-mediated hypersensitivity reactions in anaesthesia was a tryptase value exceeding twice the basal one.