The best way of measuring the extent of an individual's adherence to anti-HIV treatment is to ask "how many doses have you missed in the last fortnight?", according to a study carried out by Dr John Walsh of the Chelsea and Westminster Hospital, London.
Dr Walsh questioned 70 patients receiving HAART and compared their responses to six questions on their pill taking behaviour with data gathered from computer chips in pill bottle caps which tracked when the bottles were opened. The study set out to determine which measures were best at detecting any missed doses.
He found that 33% of patients remembered incorrectly when asked "When did you last miss a dose". In contrast, when asked "How many doses did you miss in the last two weeks, the last three days and yesterday" 21%, 21% and 14% remembered incorrectly. However, statistical tests proved that merely asking people about doses missed the previous day was less accurate than asking people to recall their adherence pattern over the previous fortnight.
Reference
Walsh J et al. Which are the most clinically useful questions in assessing adherence? A prospective comparative study. Sixth Annual Conference of the British HIV Association, abstract 03, 2000.