Diagnosis of immediate-type beta-lactam allergy in vitro by flow-cytometric basophil activation test and sulfidoleukotriene production: a multicenter study.

INTRODUCTION: This multicenter study aimed to evaluate the diagnostic value of 2 cellular tests based on basophil reactivity--the basophil activation test (BAT, Flow-CAST) and the sulfidoleukotriene release assay (CAST-ELISA)--in immediate-type beta-lactam allergy, particularly in patients with a clinical history of allergy and a negative skin test result. MATERIAL AND METHODS: In a multicenter study encompassing 10 European centers, 181 patients with a history of immediate-type beta-lactam allergy, and 81 controls, we evaluated the diagnostic efficiency of specific IgE determinations and of 2 cellular tests based on basophil reactivity, the BAT and the sulfidoleukotriene release assay. RESULTS: With Flow-CAST, sensitivity varied for individual beta-lactam allergens from 16% for penicilloyl-polylysine to 33% for amoxicillin, reaching 50% when all 5 allergens were considered. In beta-lactam-allergic patients with negative skin test results (22.8%), Flow-CAST showed positive results for at least 1 of the 5 allergens in 37%. Specificity varied from 89% to 97%, depending on the allergens used. In CAST-ELISA, the overall sensitivity in skin test-positive patients was 41.7%; in patients with negative skin test results it was 27.9%. Both tests were not absolutely correlated, so that when all the results were considered together, sensitivity increased to 64.3% and specificity varied for both tests combined from 73% to 92%. In contrast, specific IgE determinations in the same population yielded a lower sensitivity (28.3%). CONCLUSIONS: A diagnostic algorithm including skin tests and specific IgE, followed by cellular tests in negative patients and controlled challenge enabled us to confirm beta-lactam allergy in 92% of cases. This procedure would also allow us to avoid two-thirds of the required controlled challenges.

Diagnostic tests based on human basophils: more potentials and perspectives than pitfalls. II. Technical issues.

Cellular basophil activation tests (BAT) such as histamine or sulfidoleukotriene-release tests for allergy diagnosis have been available for some time, but expression of basophil-activation markers such as CD63 and CD203c detected by flow cytometry has attracted particular attention in recent years. Not only the potential but also the possible pitfalls of flow-cytometric BAT have been stressed recently. Some authors have suggested that the technical problems are still such that BAT should only be performed in specialist laboratories. In an earlier review based on our clinical experience obtained over several years, we showed that, even using different protocols, reproducible and meaningful clinical results can be obtained. In this paper, we review the current knowledge in relation to several technical issues and show that flow-cytometric BAT already represents a major advance in the field of in vitro allergy diagnosis. We conclude that there are no serious technical justifications for depriving allergic patients of clinically indicated BAT tests, which can be performed reliably by any laboratory with the appropriate experience in allergy diagnosis and flow cytometry.