Sensitivity and specificity of the lymphocyte transformation test in drug reaction with eosinophilia and systemic symptoms causality assessment

Summary Background Drug reaction with eosinophilia and systemic symptoms ( DRESS ) is a severe delayed hypersensitivity reaction. The determination of drug causality is complex. The lymphocyte transformation test ( LTT ) has been reported positive in more than 50% of DRESS cases. Nevertheless, the sensitivity and specificity of LTT specifically in DRESS have not yet been established. Rechallenge with the culprit drug is contraindicated and cannot be used as gold standard for sensitivity and specificity determination. Objective To estimate the sensitivity and specificity of LTT in a clinically defined series of patients with DRESS . Methods Some 41 patients diagnosed with DRESS were included in the study. The results of the algorithm of the Spanish Pharmacovigilance System were used as the standard for a correct diagnosis of drug causality. A standard LTT was performed with involved drugs in acute or recovery samples. A stimulation index ( SI ) ≥2 in at least one concentration except for beta‐lactams ( SI ≥3) and contrast media ( SI ≥4) was considered positive. Contingency tables and ROC curves were used for analysis. Results Sensitivity and specificity of LTT in the recovery phase of DRESS were 73% and 82%, respectively, whereas in the acute phase, they were only 40% and 30%, respectively. Comparison of skin tests and LTT confirmed a higher sensitivity and specificity of LTT in DRESS . LTT showed high sensitivity (S) and specificity (Sp) for anticonvulsants (S 100%, Sp 100%; P = .008), anti‐ TB drugs (S 87.5%, Sp 100%; P = .004), and beta‐lactams (S 73%, Sp 100%; P = .001). ROC curves revealed that the best criteria for LTT positivity for all drugs are SI ≥2 in at least one concentration, increasing overall sensitivity to 80%, and for beta‐lactams from 73% to 92%. Conclusions and clinical relevance LTT is a good diagnostic tool for drug causality in DRESS , mainly when performed in the recovery phase.