Phenotyping of N-acetyltransferase type 2 by caffeine from uncontrolled dietary exposure.

Background and objective The standard approach for phenotyping of the human arylamine N-acetyltransferase 2 (NAT2) uses urinary caffeine metabolite ratios after a caffeine test dose taken in after methylxanthine abstinence. We tested whether these standardization measures were still needed when a more sensitive quantification technique was used.