Basophil Activation Tests: A Diagnostic Break-Through in Opiate Allergy

416 http://e-aair.org We have read the manuscript about codeine (3-methylmorphine) anaphylaxis by Yoo et al. with great interest and would like to take the opportunity to raise some issues and communicate our experience. As recently reviewed, despite their frequent and ubiquitous use, genuine IgE-mediated allergy to opiates remains exceedingly rare. Also, correct diagnosis is not straightforward, mainly because of uncertainties associated with measurement of drug-specific IgE antibodies and skin testing. Actually, the key to correct diagnosis of opiate allergy lies in elucidating the clinical significance of positive specific IgE (sIgE) results and distinguishing skin test responsiveness resulting from direct histamine release from a true IgE-mediated activation of cutaneous mast cells. From investigations about morphine and pholcodine (3-[2-morpholinyl-ethyl] morphine)-reactive IgE antibodies it is clear that positive IgE results towards these compounds cannot be considered as a proof for opiate allergy. As a matter of fact, sIgE reactivity to opiates has been observed in up to 10% of the general population and over 80% of patients allergic to rocuronium. Mutatis mutandis, this observation applies to skin testing with these potent histamine releasers that, for years, have been used as a positive control in skin testing (for review). In contrast, opiates seem not to trigger histamine release from human basophils, making these cells highly attractive as a complementary diagnostic instrument to discriminate non-immunologic hypersensitivity reactions from genuine allergy with an underlying IgE-mediated mechanism (for review). In their manuscript the authors describe a patient who suffered from anaphylaxis due to oral intake of codeine and document their diagnosis with a drug provocation and histamine release tests. However, due to the unavailability of codeine-sIgE tests, they were unable to establish a potential IgE-mediated mechanism. However, several points might be addressed here. First, measurement of pholcodine and morphine sIgE antibodBasophil Activation Tests: A Diagnostic Break-Through in Opiate Allergy