Acetylator phenotyping: a comparison of the isoniazid and dapsone tests

A comparison was made between the results of acetylator phenotyping by isoniazid (INH) half-life measurements based on 5 samples (0-6 h), and by determination of the ratio of monoacetylated (MAD) to unchanged dapsone (DDS) in a single sample obtained 3 h after dapsone intake. In each of 44 subjects examined, there was unequivocal agreement about classification of the subject as a rapid (INH t1/2 less than 2 h; MAD/DDS greater than 0.3) or slow (INH t1/2 greater than 2 h; MAD/DDS less than 0.3) acetylator. It appears that the single-sample (3 h) dapsone test is as reliable as the more laborious and time-consuming INH test for acetylator phenotyping.