[Cellular antigen stimulation test (CAST)--applicability in the diagnosis of insect toxin allergies]

In the CAST, blood leukocytes are prestimulated with the cytokine IL-3 and exposed to allergen(s). Mainly basophiles react by synthesizing sulfidoleukotrienes (sLT), namely LTC4 and its metabolites LTD4 and LTE4. They are detected by ELISA technique. 66 patients with suspected allergy to hymenoptera venoms were evaluated. Allergic reactions comprised all severity grades (I-IV ref. H. L. Mueller). The workup included skin tests (up to 1 microgram/ml, Pharmacia), measurement of specific serum IgE with RAST-CAP (Pharmacia), and CAST with three concentrations of bee (Apis mellifera) and wasp (Vespula spec.) venom (Aquagen ALK). A control group of 13 nonallergic, RAST-CAP negative individuals was established. CAST demonstrated pronounced variations of individual s-LT synthesis in patients and controls. The use of elevated cut-offs improved the results, while the use of three allergen concentrations did not increase reliability. Diagnostic accuracy of CAST was evaluated by comparison with skin tests as the "gold standard". With bee venom and a cut-off at 3 standard deviations, a sensitivity and specificity of 73%/71% was obtained. Wasp venom showed better results at 2 standard deviations, with a sensitivity and specificity of 68%/100%. CAST results were not influenced by the severity of the allergic reaction nor by the time lapse since the sting had occurred. In conclusion, CAST is a valuable test in insect sting allergy. However, established methods such as skin tests and RAST-CAP achieve better results. CAST should therefore be considered a supplementary method in cases where established methods fail. It remains to be shown whether CAST can be used as a parameter for monitoring patients who have undergone immunotherapy.