Background: The potential benefits of anti-retroviral therapy for HIV is not fully realized because of difficulties in adherence with demanding treatment regimens, especially among injection drug users.
Methods: HIV-positive methadone patients who were less than 80% adherent with their primary anti-retroviral therapy were randomized to a trial of incentives for on-time adherence. Adherence was rewarded with an escalating scale of vouchers redeemable for goods. Both intervention and control group visited a medication coach twice a month. The cost of the intervention was determined by micro-costing. Other costs were obtained from administrative data and patient report of out-of-system care.
Results: During the 12-week intervention period, the incremental direct cost of the intervention, including treatment vouchers, was $942. The voucher group incurred $2572 in anti-retroviral drug cost, significantly more than the $1973 incurred by the comparison group (p<.01). Adherence, as measured by on-time openings of an electronically monitored vial, was 78% in the intervention group and 56% in the control group.
Conclusions: The incremental direct cost of voucher incentives was $292 per month. If the observed increase in adherence from voucher incentives can be sustained in the long-term, the literature suggests that disease progression will be slowed. Further research is needed to evaluate if the improvement can be sustained or achieved at lower cost. Mitigation of treatment resistance and reduction in HIV transmission are additional benefits that favor adoption.