Pill-based pre-exposure prophylaxis using tenofovir disoproxil fumarate/emtricitabine and tenofovir alafenamide/emtricitabine are extremely effective at preventing HIV when used correctly. However, regular pill-taking may not be for everyone – it can be challenging to remember to take pills on time, for example, and for others, pill-taking can be challenging because of privacy concerns, inconvenience or other reasons. Fortunately, a variety of new HIV prevention products are currently in development, each with unique attributes that may appeal differently to different users. For example, long-acting injectable agents are on horizon, and efforts have long been underway to develop gels or other products that could be applied rectally. Understanding people’s preferences towards these various products and their characteristics can be useful to inform how they should be rolled out at the population level in the future.
A discrete choice experiment (DCE) is a survey-based method rooted in health economic and decision sciences theory that aims to quantify such preferences from the end-users’ perspective. We used a DCE to characterize preferences for existing and forthcoming PrEP modalities among gbMSM in Toronto, between May-August 2016.
Participants completed a survey containing 12 choice sets that comprised the DCE. Each choice set consisted of two hypothetical PrEP alternatives, and a status quo condition (Figure), and they were asked which of the three alternatives they most preferred. Each alternative was described by a set of attributes, each with a defined number of levels. We analyzed the results using a mixed multinomial logit model. To make the results of the statistical model more interpretable, we then ‘rescaled’ them so that each hypothetical form of PrEP could be given a final ‘utility’ score that measures the study sample’s overall preference for its corresponding combination of attributes. The combination of least preferred attributes was zero, and the combination of most preferred attributes was 100. You can view these utilities yourself by using the Excel spreadsheet here:
Our lab is currently designing additional DCE studies to better understand PrEP-related preferences using updated data on the most promising forms of long-acting PrEP currently in development. Stay tuned for more!
Figure 1. Sample Choice Set