Lymphocyte transformation studies in suspected hypersensitivity to trimethoprim-sulphamethoxazole.

In a group of patients with suspected and probable adverse skin reactions to trimethoprim-sulphamethoxazole, the lymphocyte transformation test (LTT) was positive in approximately 60% of subjects tested. Levels of stimulation in the majority of cases were low, probably reflecting either use of inappropriate stimulatory forms of the drug or lack of marked reactivity. Since there appeared to be a correlation between peak stimulatory index and duration of the rash, the latter explanation appeared more likely.