Lymphocyte stimulation test with tetrazolium-based colorimetric assay for diagnosis of drug-induced allergic hepatitis.

The lymphocyte stimulation test (LST) is useful for diagnosing drug-induced allergy and identifying the causative drug. In this study, we examined the usefulness of 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) as a marker for LST in diagnosing drug allergy. In a basic study using normal peripheral blood mononuclear cells, the normal range of stimulation index (SI) was 0.92-1.38, and the mean SI for all drugs tested was 1.134 +/- 0.111 (mean +/- S.D.). The cut-off value of SI for diagnosis of drug allergy was thus set at over mean + 2S.D. for possibly positive, and at over mean + 3S.D. as a definitely positive reaction. Forty-six cases of suspected drug-induced allergic hepatitis involving 85 drugs were diagnosed by this assay, and the possibly positive and definitely positive rates were 54.3% (SI > or = 1.4) and 41.3% (SI > or = 1.5), respectively. A clinical study was made of 113 patients with diagnosed drug-induced allergic hepatitis. Forty-nine (43%) of the patients were male and 64 (57%) were female. In 85% of cases the allergic reaction occurred within one month of taking medication, but there were a number of cases in whom onset occurred after long-term incubation. The main clinical symptoms were jaundice, itching, eruption, fever, and general malaise. In about 75% of cases glutamic oxaloacetic transaminase (GOT) or glutamic pyruvic transaminase (GPT) returned to normal range within one month after medication was halted.(ABSTRACT TRUNCATED AT 250 WORDS)