Evaluation of testing for specific ige to morphine, pholcodine and chlorhexidine in cases of perioperative anaphylaxis

Abstract

Background Neuromuscular blocking agents (NMBAs) are the most frequently reported causative agents in cases of anaesthetic related anaphylaxis. Assays for specific IgE (sIgE) to morphine and pholcodine are available as indicators of sIgE to the substituted ammonium groups on NMBAs. Chlorhexidine is an antiseptic also implicated in perioperative anaphylaxis. Aim To evaluate laboratory tests for sIgE to morphine, pholcodine and chlorhexidine in the investigation of perioperative anaphylaxis. Method This study included 140 patients referred to the Anaesthesia Allergy and Adverse Events clinic at Royal North Shore Hospital. Standardised skin tests were performed with all suspected agents to which patients had been exposed. Testing for sIgE to morphine, pholcodine and chlorhexidine was performed via the Phadia ImmunoCAP system. Results Using the recommended cut-off value sIgE tests for morphine, pholcodine and chlorhexidine all showed good sensitivity and specificity with reference to skin test results. ROC analysis suggested an alternative positive cut-off. Application of this lower threshold allowed for increased sensitivity without adversely affecting specificity. Conclusion Specific IgE testing to morphine, pholcodine and chlorhexidine is a reliable adjunct to skin testing in determining diagnosis of allergy to NMBAs and/or chlorhexidine. Additionally, adjustment of cut-off thresholds is able to increase test sensitivity.