Background: Neuromuscular blocking agents (NMBA) are responsible for most immediate hypersensitivity reactions during anesthesia, as a result of the presence of a quaternary ammonium ion. The aim of this study was to evaluate the diagnostic performance of a commercial immunoglobulin E (IgE) test (quaternary ammonium morphine [QAM]) for diagnosing sensitivity to NMBA.
Methods: We tested 168 patients exposed to NMBAs during anesthesia. Of those patients, 54 had an uneventful procedure and 114 had immediate hypersensitivity reactions, and 57 patients had positive skin tests to the administered NMBA, whereas 57 had negative skin tests. Specific IgE concentrations determined with the QAM method based on a morphine solid phase were compared with those obtained with a recommended experimental method with a choline solid phase.
Results: For the QAM test, a 0.35 kUA/l positivity cutoff was chosen from the receiver operating characteristics curve. QAM-specific IgE was found in 84.2% of skin test-positive reactors (80.7% with the recommended method; no significant difference), and binding was inhibited by the culprit NMBA in 80% of cases. The frequency of QAM-specific IgE positivity was significantly higher in skin test-negative reactors (24.6%) than in controls (9.3%), suggesting NMBA sensitivity.
Conclusion: Sensitivity of the QAM test (84.2%), together with its simplicity and suitability for routine laboratory use, makes it a valuable tool, in conjunction with skin tests, for diagnosing NMBA sensitivity in patients who react after NMBA injection. The QAM test is of particular interest when skin tests are not available or not reliable or give results poorly compatible with mediator release or clinical features.