Morphine-specific IgE Testing in the Assessment of Neuromuscular Blocking Agent Allergy. Comment on Br J Anaesth 2024; 132: 193–5

Editor—We read with interest the correspondence by Chow and colleagues 1 Chow K.L. Patchett K. Reeves G. de Malmanche T. Gillies D. Boyle M. Morphine-specific IgE testing in the assessment of neuromuscular blocking agent allergy: a single centre experience. Br J Anaesth. 2024; 132: 193-195 Abstract Full Text Full Text PDF PubMed Scopus (1) Google Scholar on morphine-specific IgE testing. However, we would like to bring to highlight some studies that have already provided important information regarding the potential and limitations of ImmunoCAP specific (s)IgE morphine as a diagnostic tool for neuromuscular blocking agent (NMBA) allergy. Shortly after its introduction, the diagnostic utility of the ImmunoCAP sIgE assay was explored in 2007 by our group. 2 Ebo D.G. Venemalm L. Bridts C.H. et al. Immunoglobulin E antibodies to rocuronium: a new diagnostic tool. Anesthesiology. 2007; 107: 253-259 Crossref PubMed Scopus (103) Google Scholar From that study, it emerged that the traditionally recommended threshold of 0.35 kUA L−1 is appropriate and that the application of a lower allergen-specific threshold did not benefit performance. This observation was later confirmed by Laroche and colleagues, 3 Laroche D. Chollet-Martin S. Léturgie P. et al. Evaluation of a new routine diagnostic test for immunoglobulin E sensitization to neuromuscular blocking agents. Anesthesiology. 2011; 114: 91-97 Crossref PubMed Scopus (65) Google Scholar but not by Anderson and colleagues, 4 Anderson J. Green S. Capon M. et al. Measurement of pholcodine-specific IgE in addition to morphine-specific IgE improves investigation of neuromuscular blocking agent anaphylaxis. Br J Anaesth. 2020; 125: e450-e452 Abstract Full Text Full Text PDF PubMed Scopus (5) Google Scholar who reported on an optimal cut-off of 0.19 kUA L−1. However, it has been consistently demonstrated that the morphine-based assay exhibits several limitations that seem to prevent its standalone use for documenting IgE-mediated allergy to NMBAs. Morphine-specific IgE testing in the assessment of neuromuscular blocking agent allergy: a single centre experienceBritish Journal of AnaesthesiaVol. 132Issue 1PreviewEditor—Neuromuscular blocking agents (NMBAs) are a frequent cause of perioperative reactions.1 In 1983, Baldo & Fisher2 identified the allergenic site of alcuronium as the substituted tertiary or quaternary ammonium ions, also present in other NMBAs, morphine, and later also demonstrated in pholcodine.2,3 They reported that morphine-specific immunoglobulin E (sIgE) determined by radioimmunoassay (RIA) was superior to specific NMBA-IgE RIA, suggesting that morphine-sIgE be routinely implemented in the assessment of NMBA anaphylaxis. Full-Text PDF