THE FREQUENCY AND CLINICAL-SIGNIFICANCE OF SPECIFIC IGE TO BOTH WASP (VESPULA) AND HONEYBEE (APIS) VENOMS IN THE SAME PATIENT

Background Changeover from Phadebas RAST to Pharmacia AutoCAP increase d double-positivity to both honey-bet and common wasp (vespula) venom in our patients.Objective We examined the frequency of IgE double-posi tivity, its clinical relevance and utility in investigating potentiall y allergic patients. Methods One hundred and eighty-two patients with hymenoptera allergy were tested using PAST (n = 51) and AutoCAP (n = 1 31) assays over 4 years. Patients had a history of reactions to vespul ae (22), honey-bet (10) and unidentified hymenoptera (vespinae) (7). R esults After changing from PAST to AutoCAP double-positivity increased from 10 (5/ 51) to 30% (39/131) (P < 0.01). RAST and CAP assays gave similar median class results (vespula = 3, honey-bee = 2), Thirty-six CAP patients had systemic reactions of Mueller grade Il and above. In vespula-allergic double-positive subjects, high CAP classes (greater t han or equal to class 3) to honey-bet were common (30%). In 25% the CA P classes were equal. In honey-bee-allergic subjects, all vespula veno m CAP IgE was low titre (class 1 or 2) and 20% were equal for both ven oms. In 43% of vespinae-allergic patients the CAP class was equal to b oth (class 2 and 3). In contrast, intradermal skin test double-positiv ity was uncommon. Double-negative skin test results were common in the CAP double-positive population (22% of honey-bee-allergic. 13% of ves pula-allergic and 43% of vespinae-allergic patients). Vespula allergic patients have higher bee-venom IEE than vice versa. Twenty-seven per cent of CAP double-positive patients (representing 8% of all venom all ergic patients tested over this period) had equal class IgE to both ve noms which was not helpful in diagnosis. Combination of skin testing a nd CAP is unhelpful in only 5/37 (14%) of patients with double-positiv e serology. Conclusion If used in isolation CAP may be misleading, esp ecially if only one venom is tested. Identification of the causative v enom must utilize both clinical history and skin testing in these doub le-positive patients, and challenge testing if indicated.