Diagnosis of IgE-dependent anaphylaxis to neuromuscular blocking drugs, thiopentone and opioids.

Although allergenic cross-reactivity of neuromuscular blocking drugs (NMBDs) is recognised clinically and has been firmly established at the serological and immunochemical levels, interpretation of in vitro inhibition findings for clinical purposes is not always straightforward. Points to be taken into account when considering serum IgE direct binding and inhibition results and when determining which NMBDs a patient may be sensitive to, include the relationship between in vitro potencies and clinical findings and the nature of the drug solid phase used for testing. It should also be remembered that the stimulating antigenic source for the patients' NMBD-reactive IgE antibodies is almost always unknown. A comparison of skin and IgE radioimmunoassay (RIA) tests for NMBDs in 29 patients is presented and difficulties involved in interpreting the results of both tests are discussed. Methods for increasing the detection of NMBD-reactive IgE antibodies are outlined. In screening sera of patients for IgE antibodies to thiopentone and morphine as well as NMBDs, multiple drug reactivities have been detected in a few subjects. Attention is drawn to defects in the existing thiopentone RIA although it is clear that the test is specific in patients who react to the drug. Addition of the serum tryptase assay to skin tests and IgE RIAs for NMBDs, thiopentone and morphine provides a powerful combination of diagnostic tests for the investigation of anaphylactoid reactions to anaesthetic drugs.