Hypersensitivity reactions to β-lactam are common and may be severe, these include immediate (IgE-mediated) and non-immediate reactions. The value of biological test like; basophil degranulation test, in a non-selected population of patients suspected of drug allergy has never been fully established.

We randomly studied 35 patients who consulted for a suspected immediate hypersensitivity reaction to β-lactams. Clinical history, skin tests or drug provocation test (DPT) and/or serum specific IgE antibodies were performed to establish the diagnosis of allergy to β-lactam. The Basotest, based upon the expression of CD63 in the presence of specific allergens was evaluated as biological test to confirmed the clinical analysis in this unselected population. 35 β-lactam suspected allergic patients (13 urticaria, 9 macula papular eruption, 7 choc, 3 angioedema), 40 atopic subjects non-allergic to β-lactam were studied. History, provocation test and Basotest, to detect a specific sensitization to β-lactam were studied in all subjects.

No statistical difference in the basal CD63 expression was observed between basophils of β-lactam allergic patients and those from control subject. In the 35 β-lactam allergic patients, Basotest, was positive in 3 subjects, two with a confirmed allergy (amoxicillin or ceftriaxon) and another one with a negative DPT (ceftriaxon), all control were negative.

This study does not confirm the data of Sanz et al (Clin Exp Allergy 2002) who used a different method of activation of basophils and analysis method. Thus, the Basotest® cannot be used in patients with immediate hypersensitivity reactions to β-lactams.