Hymenoptera venom allergy: taking the sting out of difficult cases.

BACKGROUND Correct identification of the culprit venom is a prerequisite for specific venom immunotherapy. OBJECTIVE To assess whether the basophil activation test (BAT) constitutes an additional diagnostic instrument in patients with equivocal or negative specific immunoglobulin (Ig) E or venom skin test (VST) results. METHODS One hundred eighteen patients with a compelling history of IgE-mediated hymenoptera venom allergy were enrolled. Venom-specific IgE was quantified by ImmunoCAP and VST was performed in all patients. Basophil activation was analyzed by flow cytometry after labeling with anti-IgE and anti-CD63. RESULTS In 64 out of 118 patients, diagnosis was considered as definite and the entomologic description was confirmed by unequivocal and concordant positive specific IgE and VST results. In 53 of those 64 patients, BAT confirmed diagnosis, whereas the remaining 11 patients were nonresponsive in the BAT analysis. Forty-seven patients (40%) had a tentative diagnosis of venom allergy, as they had divergent specific IgE or VST results. In 31 of those patients, BAT was positive only for the suspected venom and helped to establish diagnosis of wasp and honeybee venom allergy in 28 and 3 patients, respectively. BAT was diagnostic in 7 patients with complete negative results for specific IgE and VST, despite clear entomologic identification. CONCLUSIONS In about half the patients with diagnosis of venom allergy, unequivocal specific IgE and VST results are obtained and additional tests are not needed. In the remainder, diagnosis is less straightforward due to discrepant or negative specific IgE orVST results. In these patients, BAT constitutes a helpful additional instrument to identify the culprit venom and start venom immunotherapy accordingly.