Validation of a flow cytometric assay detecting in vitro basophil activation for the diagnosis of muscle relaxant allergy.

BACKGROUND: Anaphylactic reactions during anesthesia are mainly the result of muscle-relaxant (MR) drugs. Skin tests, serologic detection of specific IgE, and in vitro leukocyte histamine release are used to investigate MR allergy. OBJECTIVE: We describe a new assay that is based on the detection by flow cytometry of the altered expression of plasma membrane molecules of MR-activated basophils. METHODS: For this assay, which we have named the BASIC assay, basophils are incubated in vitro with MR, after which they are fixed and then triple labeled with fluorescein-conjugated anti-CD63, tandem dye R-phycoerythrin-cyanin 5.1 conjugated anti-CD45, and R-phycoerythrin conjugated anti-IgE. The resulting B asophils' A ltered S urface I mmunofluorescence is detected by flow C ytometry (BASIC). RESULTS: Forty-one patients who had an allergic reaction during general anesthesia and 23 control subjects without such a history were studied. All included subjects' basophils were tested in the BASIC assay with at least 4 MR: suxamethonium, gallamine, vecuronium, and pancuronium. After reaction of the basophils of the MR-allergic patients with MRs, increased surface expression of CD63 and CD45 and decreased expression of IgE were detected. Increased expression of CD63 was observed most frequently and it was stronger than the alteration of the 2 other markers. Cross-reactivity between MRs commonly occurred. MRs diluted 10(-1) activate the basophils of the control subjects, suggesting that at relatively high concentrations MRs are also nonspecific basophil activators. CONCLUSION: In the diagnosis of MR allergy, the BASIC assay has a good specificity but a low sensitivity, and it correlates strongly with skin test results. It is currently appraised for the diagnosis of anaphylactic reaction induced by other classes of drugs.

Anaphylaxis to muscle relaxants: cross-sensitivity studied by radioimmunoassays compared to intradermal tests in 34 cases.

Thirty-four patients (31 female and three male patients) with a previous anaphylactoid shock to muscle relaxants were investigated. The seric antimyorelaxant IgE was detected by radioimmunoassay (RIA), and the results were compared to intradermal test (IDR) reactions to dilutions of the commercial drugs. The RIA was carried out with a Sepharose-myorelaxant solid phase and anti-IgE 125I-labeled IgG. The results corresponded to the percentage of labeled anti-IgE bound on the solid phase. The RIA with Sepharose-alcuronium and Sepharose-choline was estimated positive from determination with normal sera (n = 12) when bound IgE was greater than 1.0% and 1.5%, respectively. The RIA and IDR were positive in 43.5% and 75%, respectively, of the cases, with a concordance of 66%. One test at least was positive in 79.4% of the cases. No correlation was found between IgE seric levels and the RIA nor between the cutaneous sensitivity and the RIA. Cross-reactivity with Sepharose-choline and Sepharose-alcuronium was observed in 50%, and it was demonstrated by IDR in only 34.2%. The RIA demonstrated the specificity of IgE to quaternary ammonium compounds as myorelaxant drugs. The positive IDR revealed the bridging of mast cell-bound specific IgE, depending on structural conditions, such as the flexibility of the molecules or the variable specificity of the antibodies, restricted to quaternary ammonium ions or enlarged to a broader part of the incriminated molecules.

Cross-reactivity of metocurine, atracurium, vecuronium and fazadinium with IgE antibodies from patients unexposed to these drugs but allergic to other myoneural blocking drugs.

An inhibition assay was used to determine quantitatively the allergenic cross-reactivity of some myoneural blocking drugs not yet released for use in Australia, in the sera of patients who had experienced anaphylactic reactions to neuromuscular blocking drugs. Two of the compounds, metocurine and atracurium were highly cross-reactive with the currently used myoneural blockers; fazadinium was weakly cross-reactive and vecuronium intermediate in potency between these two extremes. From these results, we predict that anaphylactic reactions to these compounds, and particularly to metocurine and atracurium, will occur in some patients allergic to the currently used neuromuscular blocking agents.