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Basophil Activation Test Application in Drug Hypersensitivity Diagnosis: An Empirical Approach

Background: The diagnosis of drug hypersensitivity reactions (DHRs) is based both on clinical history and in vivo tests, such as specific IgE and cutaneous tests, when available. Objectives: The aim of this work was to evaluate the basophil activation test (BAT) as a supplementary tool for drug challenges and drug allergy diagnosis. Method: We evaluated 204 outpatients reporting DHRs. Available serum-specific IgE drugs were determined and cutaneous tests were performed when appropriate. BAT was performed immediately after blood sampling. The expression of CD63 was evaluated with flow cytometry. The test was considered positive when CD63 expression was > 5% and the stimulation index (the ratio of the percentage of CD63-expressing cells with drug exposure/percentage of CD63-expressing cells with wash buffer) was > 2. Patients who reported mild to severe reactions and those with a discrepancy between clinical history and BAT underwent a challenge test. Results: The drugs that caused adverse reactions were mainly antibiotics (49%). Non-steroid anti-inflammatory drugs (NSAID) were cited as responsible for DHRs in 37%, with the remaining 14% being due to other drugs. BAT revealed a high specificity (92%) and low sensitivity for antibiotics (40%). For the suspected reactions to penicillin, both the in vitro tests supported 94% of the diagnoses. We also observed a high specificity in the case of challenge with NSAIDs (100% specificity). Conclusions: BAT is effective in discriminating adverse drug reactions, whilst only more critical cases require integrated evaluations and more complex clinical examinations. It is relevant that the concordance of anamnesis and in vitro tests reduce the need for challenge testing, limiting them to selected cases.