Immunoglobulin E antibodies to rocuronium - A new diagnostic tool

Background: Diagnosis of allergy from neuromuscular blocking agents is not always straightforward. The objectives of the current study were to investigate the value of quantification of immunoglobulin E (IgE) by ImmunoCAP (Phadia. AB, Uppsala, Sweden) in the diagnosis of rocuronium allergy and to study whether IgE inhibition tests can predict clinical cross-reactivity between neuromuscular blocking agents. Methods: Twenty-five rocuronium-allergic patients and 30 control individuals exposed to rocuronium during uneventful anesthesia were included. Thirty-two sera (total IgE > 1,500 kU/1) were analyzed for potential interference of elevated total IgE titers. Results were compared with quantification of IgE for suxamethonium, morphine, and phokodine. Cross-reactivity between drugs was assessed by IgE inhibition and skin tests. Results: Sensitivity of IgE for rocuronium, suxamethonium, morphine, and phokodine was 68, 60, 88, and 86%, respectively. Specificity was 100% for suxamethonium, morphine, and phokodine IgE and 93% for rocuronium IgE. ROC analysis between patients and control individuals changed the threshold to 0.13 kUa/1 for rocuronium, 0.11 kUa/1 for suxamethonium, 0.36 kUa/1 for morphine, and 0.43 kUa/1 for phokodine. Corresponding sensitivity was 92, 72, 88, and 86%, respectively. Specificity was unaltered. interference of elevated total IgE with quantification of IgE was demonstrated by the analysis in sera with a total IgE greater than 1,500 kU/1. IgE inhibition did not predict clinical relevant cross-reactivity. Conclusions: The rocuronium ImmunoCAP constitutes a reliable technique to diagnose rocuronium allergy, provided an assay-specific decision threshold is applied. IgE assays based on compounds bearing ammonium epitopes are confirmed to represent reliable tools to diagnose rocuronium allergy. High total IgE titers were observed to affect specificity of the assays.