October 26, 2002
Adherence remains one of the most important determinants of successful HIV therapy, and one of the least understood. Valerie Stone at Massachusetts General Hospital has made many contributions to this field. In this study, she adopted the methods of market research to try and dissect the relative importance of different factors on patients' prediction of their ability to adhere. The marketing industry has become far more sophisticated than social scientists at understanding how we make choices.
It is widely assumed that simply switching to once-daily therapy will improve adherence and outcome, but this has not been proven. In fact, it may not be true. Once-daily therapy, using current regimens, may increase the number of pills, and may impose food requirements. Dr. Stone's team (which included professional market researchers) used the methods of conjoint analysis to examine patients' preferences for five different regimens, which allowed them to look at the role of individual features of a regimen in the choice.
They studied 299 patients who were taking three-drug HAART, and administered a survey instrument with trained interviewers. Patients compared seven regimens using currently available drugs and compared each regimen with each other regimen. The regimens ranged from 13 pills daily divided twice daily with a food restriction (i.e. nelfinavir based), to two pills daily taken without food, to three different once-daily regimens. Of these, only one regimen allowed the drugs to all be taken simultaneously. In addition, the number of bottles, prescriptions, and the co-pays were specified.
Ten attributes were studied as predicting adherence. All were perceived as important, led by number of pills, dosing frequency, and the side effect profile. The ideal regimen would be two or fewer pills, taken once a day -- without regard to food -- and the pills would be small.
The ideal regimen would also involve one bottle, one prescription, and one co-pay. No current regimen fits these characteristics. Although the participants expressed a preference for once a day, given the choices offered, the regimen that involved one prescription, one co-pay, and two pills a day was slightly favored, even though it was twice daily.
This study has some limitations. First, the patients were asked to predict the likelihood of adherence but it is unclear that this really would predict their behavior. Second, the outcome was affected by the choice of regimens offered, based on what was available at the time. As regimens and formulations change, the choices may be different.
However, this study is significant in several ways. First, it points out that adherence is a complex process, and there are no simple answers. In addition to the frequency of dosing, pill size, pill number, the number of bottles and the number of co-pays are important. One size will not fit all.
Second, no specific characteristic of patients predicted their preferences; instead, there was substantial variation among patients in their preferences. Lastly, it is important to use sophisticated tools that exist to understand how we make choices. If these tools help marketers understand how we choose between cars, we should take advantage of them in helping patients choose the right regimen.
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