Application of Lymphocyte Transformation Test (LTT) in Delayed Drug Hypersensitivity Reactions in a Drug Allergy Unit in Spain: a Descriptive Study

RATIONALE: Descriptive study of LTT application in delayed drug hypersensitivity reactions in a Spanish Drug Allergy Unit. METHODS: Measurement of proliferative response of T cells by LTT in adult patients with delayed drug hypersensitivity reactions evaluated in the Drug Allergy Unit, following Pichler's technique. Stimulation index > 3 was considered positive, particularly if the test was positive in more than one concentration, and a stimulation index of 2-3 weakly positive. Clinical and analytical data (type of reaction, suspect drugs, eosinophils count and hepatic profile blood test, treatment received, concomitant medication, cutaneous and epicutaneous tests) were compiled. RESULTS: Twenty-eight patients (14 female, 14 male) with suspicion of delayed drug hypersensitivity reactions were evaluated. Clinical diagnosis were maculopapular exanthema, exudative erythema multiforme, drug-induced hypersensitivity syndrome (or DRESS), Stevens-Johnson syndrome, toxic epidermal necrolysis and acute generalized exanthematous pustulosis. LTT was clearly positive in 13 patients and the elicitors drugs were beta-lactams, isoniazid, acetaminophen, ambroxol, iodinated contrast agents, lorazepam, diltiazem and omeprazole. In 10 patients the test was negative and in 5 cases was doubtful. CONCLUSIONS: LTT is a helpful tool, by complementing other tests in the diagnosis of delayed drug hypersensitivity reactions, especially in severe ones in which challenge test is contraindicated.