Two new rapid HIV tests by Alere™ have the potential to substantially decrease the window period for rapid tests. First, the Alere™ HIV Combo is a rapid fourth generation test. The performance in a laboratory based setting was recently assessed at the Thai Red Cross Anonymous Clinic Laboratory in Bangkok, Thailand (personal communication). Of 50 confirmed acute HIV samples, Alere™ HIV Combo could detect 37 (74%), while none of these 50 cases could be identified by the currently used third generation tests. These data have not yet been published, but the preliminary results indicate a very favorable performance of the Alere™ HIV Combo in a facility-based laboratory setting.

Second, the Alere™ q HIV-1/2 Detect is a qualitative, cartridge based, nucleic acid amplification test designed for Point of Care use. Data from several early infant diagnosis studies in Sub-Saharan African countries have assessed the performance of the Alere™ q HIV-1/2 Detect. The test was performed in the field, by a range of health professionals, from nurses and laboratory technicians to medical doctors. The pooled analysis showed a sensitivity of 99.07% (95%CI 95.48 - 99.95%) and a specificity of 99.94% (99.72-100%).

This will be a prospective study, collecting blood samples from individuals receiving PrEP at one of two drop-in centers in Bangkok, Thailand:

Rainbow Sky Association of Thailand (RSAT) and Service Worker IN Group (SWING). RSAT is a community-based organization for people with sexual diversity (MSM, gay, transgender, lesbians, and bisexual), and has specific programs for MSM, transgender and lesbian health. SWING promotes HIV prevention among male and female sex workers and provides both community outreach and clinical services at their center. Both locations offer PrEP as part of their service.

Participants who visit the DICs seeking to receive PrEP will undergo HIV testing at several time points: before receiving PrEP (Month 0), one month after starting PrEP (Month 1), three months after starting PrEP (Month 3), and every three months thereafter.

The routine HIV testing algorithm in the DIC is as follows:

• Determine® HIV-1/2 (Alere Medical Co., Ltd.), if reactive followed by two other rapid 3rd generation immunochromatography anti-HIV tests. These are all rapid tests on whole blood as collected by finger prick, performed by trained community health workers in the DIC.

For the purpose of this study, two additional blood samples will be taken by phlebotomy to perform:

• The Anonymous Clinic HIV-testing algorithm (see Annex 1): Architect® HIV-1/2 Combo (Abbott), if reactive followed by Determine® HIV-1/2 (Alere) and Elecsys® HIV combi PT (Roche). Samples that are non-reactive by Architect® HIV-1/2 Combo will be tested by pooled NAAT using Aptima HIV-1 RNA qualitative assay (Hologic®) to screen for acute HIV infection. Samples that are positive by Architect®, Determine® and Elecsys® will be tested by second generation EIA (which detects IgG Ab) to identify acute HIV infection (i.e. 4th generation reactive and 2nd generation negative). This is the standard HIV testing algorithm performed at the Thai Red Cross Anonymous Clinic Laboratory and will identify acute HIV infections.
• Alere™ HIV Combo Alere™ q HIV-1/2 Detect Both the regular DIC algorithm and the Anonymous Clinic algorithm will be used as comparator methods.

Inclusion Criteria:

• Will start receiving PrEP at one of the participating clinics
• 18 years or older
• Willing to provide informed consent

Exclusion Criteria:

• Not receiving PrEP at one of the participating clinics
• HIV-infected

Participants visiting either the RSAT or SWING drop in centers in Bangkok to access PrEP will be asked to join the study.