Adherence to PrEP and HIV Risk Among People Who Inject Drugs
Adherence to PrEP and HIV Risk Among People Who Inject Drugs
The BTS was a randomized, double-blind, placebo-controlled, endpoint-driven study conducted in 17 Bangkok Metropolitan Administration (BMA) drug-treatment clinics that offer clients an HIV-prevention package, social services, and medical care. Participants chose daily visits or monthly visits and could change from daily to monthly visits or vice versa at monthly visits. At daily visits, study nurses observed participants swallow study drug, both initialed the adherence diary, and participants received 70 baht (about 1.8 US dollars) to compensate for time and travel. At monthly visits, all participants (daily and monthly) received individualized adherence counseling and 350 baht (about 9.2 US dollars) compensation and staff reviewed the diary, did a pill count, and worked with participants to resolve discrepancies. Staff gave participants appointment cards, phoned them before monthly visits, and contacted participants who missed monthly visits by phone or, if they could not contact them by phone, with a home visit.
We defined adherence as the proportion of days, recorded in the diary, that the participant took study drug. We examined adherence by age group and sex and used Wilcoxon or Kruskal–Wallis tests to assess group differences, adjusting for age with van Elteren's test. We used Spearman's correlation to assess the association between days in daily follow-up and adherence, and Cox regression for the adherence-based effectiveness analysis. We used logistic regression to evaluate demographics and risk behaviors during the 3 months before enrollment as predictors of less than 95% adherence. We chose 95% because data from PrEP trials suggest a high level of adherence is associated with protection from HIV infection. Variables associated with poor adherence in bivariable analysis (P ≤ 0.1) were evaluated in a multivariable model and retained in the final model if the P value was 0.05 or less. We included treatment group in all models and censored data at the last HIV test. We used SAS version 9.3 (SAS Institute, Cary, North Carolina, USA) for statistical analyses.
The ethical review committees of the BMA, Thailand Ministry of Public Health, and US Centers for Disease Control and Prevention approved the protocol.
Methods
The BTS was a randomized, double-blind, placebo-controlled, endpoint-driven study conducted in 17 Bangkok Metropolitan Administration (BMA) drug-treatment clinics that offer clients an HIV-prevention package, social services, and medical care. Participants chose daily visits or monthly visits and could change from daily to monthly visits or vice versa at monthly visits. At daily visits, study nurses observed participants swallow study drug, both initialed the adherence diary, and participants received 70 baht (about 1.8 US dollars) to compensate for time and travel. At monthly visits, all participants (daily and monthly) received individualized adherence counseling and 350 baht (about 9.2 US dollars) compensation and staff reviewed the diary, did a pill count, and worked with participants to resolve discrepancies. Staff gave participants appointment cards, phoned them before monthly visits, and contacted participants who missed monthly visits by phone or, if they could not contact them by phone, with a home visit.
We defined adherence as the proportion of days, recorded in the diary, that the participant took study drug. We examined adherence by age group and sex and used Wilcoxon or Kruskal–Wallis tests to assess group differences, adjusting for age with van Elteren's test. We used Spearman's correlation to assess the association between days in daily follow-up and adherence, and Cox regression for the adherence-based effectiveness analysis. We used logistic regression to evaluate demographics and risk behaviors during the 3 months before enrollment as predictors of less than 95% adherence. We chose 95% because data from PrEP trials suggest a high level of adherence is associated with protection from HIV infection. Variables associated with poor adherence in bivariable analysis (P ≤ 0.1) were evaluated in a multivariable model and retained in the final model if the P value was 0.05 or less. We included treatment group in all models and censored data at the last HIV test. We used SAS version 9.3 (SAS Institute, Cary, North Carolina, USA) for statistical analyses.
The ethical review committees of the BMA, Thailand Ministry of Public Health, and US Centers for Disease Control and Prevention approved the protocol.