A qualitative test for the determination of isoniazid acetylator phenotype

A qualitative test procedure for phenotyping isoniazid acetylators is described. It is based on a colour reaction which depends on the free sulphadimidine content in the total urine excreted over any one-hour period between 21 and 26 hours following a dose of sulphadimidine 1.0 or 1.5 g. depending on body-weight. The test correctly classified 96 per cent of 109 slow and 96 per cent of 68 rapid inactivators. Storage of urine samples at room-temperature up to 14 days did not affect the accuracy of the results