D1.229 - Limited interest of suxamethonium, rocuronium and atracurium specific IgE reagents for the diagnosis of NMBA allergy sensitization

The objective of our study was to evaluate the pertinence of using four NMBA-specific IgE (sIgE) reagents, including research-use only (RUO) products, compared to measuring only IgE specific for quaternary ammoniums.

We retrospectively tested serum samples from 36 patients who presented with a history of documented anaphylaxis, immediately after per-operative NMBA administration. We measured specific IgE (sIgE) by using ImmunoCAP™ reagents (Thermo Fisher) c260 (morphine quaternary ammonium, MQA), c202 (suxamethonium, SUX), u254 (rocuronium, ROC) and u981 (atracurium, ATR). The u254 and u981 tests are RUO. Clinical history, anaesthesia reports, and allergology consultations with skin tests (intradermal injections, IDR) were collected. When performed, IDR were carried out with dilutions of SUX, ATR, ROC, mivacurium, and cis-atracurium.

Out of the 36 patients, only 26 had complete skin tests with the 5 NMBAs. Eighteen of these had a positive skin test for at least one NMBA and all 18 patients had positive sIgE to at least one NMBA. Of the 8 patients with negative skin tests, 7 had positive sIgE against at least one of the four reagents tested (MQA, SUX, ROC, ATR). With a threshold set at 0.1 kU_A/L (or 0.35 kU_A/L), sIgE were present in 72% (or 50%) for MQA, 42% (or 22%) for SUX, 92% (or 50%) for ROC and 8% (or 3%) for ATR.

However, we found a moderate degree of agreement between skin test results and sIgE levels. Best correlations were found with a sIgE positivity threshold set at 0.1 kU_A/L for c260 (75% of agreement), c202 (70%) and u981/ATR (60%). For u254 (ROC), best agreement (56%) was when the threshold was set at 0.35kU_A/L.

Finally, the sum of c260, c202, U254 and U981 sIgE measurements does not improve the correlation of sIgE with skin test results; when compared to c260 alone (AUC = 0.81 for the sum of IgE versus AUC = 0.88 for c260 alone).

We estimate that c202, u254 and u981 ImmunoCAP reagents are not required for diagnosis of NMBA sensitization in patients with prior anaphylaxis to this class of molecules. Presence of anti-MQA IgE (c260 test) is sufficient and the choice of subsequent NMBA usage preferably relies on skin tests and/or basophil activation tests, if available.