Appointment reminders to increase uptake of HIV retesting by at-risk individuals: a randomized controlled study in Thailand.

Introduction Frequent HIV testing of at-risk individuals is crucial to detect and treat infections early and prevent transmissions. We assessed the effect of reminders on HIV retesting uptake. Methods The study was conducted within a programme involving four facilities providing free-of-charge HIV, syphilis and hepatitis B and C testing and counselling in northern Thailand. Individuals found HIV negative and identified at risk by counsellors were invited to participate in a three-arm, open-label, randomized, controlled trial comparing: (a) "No Appointment & No Reminder" (control arm); (b) "No Appointment but Reminder": short message service (SMS) sent 24 weeks after the enrolment visit to remind booking an appointment, and sent again one week later if no appointment was booked; and (c) "Appointment & Reminder": appointment scheduled during the enrolment visit and SMS sent one week before appointment to ask for confirmation; if no response: single call made within one business day. The primary endpoint was a HIV retest within seven months after the enrolment visit. The cost of each reminder strategy was calculated as the sum of the following costs in United States dollars (USD): time spent by participants, counsellors and hotline staff; phone calls made; and SMS sent. The target sample size was 217 participants per arm (651 overall). Results Between April and November 2017, 651 participants were randomized. The proportion presenting for HIV retesting within seven months was 11.2% (24/215) in the control arm, versus 19.3% (42/218) in "No Appointment but Reminder" (p = 0.023) and 36.7% (80/218) in "Appointment & Reminder" (p < 0.001). Differences in proportions compared to the control arm were respectively +8.1% (95% CI: +1.4% to +14.8%) and +25.5% (+17.9% to +33.2%). The incremental cost-effectiveness ratios of "No Appointment but Reminder" and "Appointment & Reminder" compared to the control arm were respectively USD 0.05 and USD 0.14 per participant for each 5% increase in HIV retesting uptake within seven months. Conclusions Scheduling an appointment and sending a reminder one week before was a simple, easy-to-implement and affordable intervention that significantly increased HIV retesting uptake in these at-risk individuals. The personal phone call to clients probably contributed, and also improved service efficiency.