There are two stages in the study. In Stage 1, 2000 Thai MSM, MSW and TGW/TGSW will be screened at the Thai Red Cross Anonymous Clinic (TRCAC) or Besides walk-in clients of TRCAC, potential participants could be referred to TRCAC by Rainbow Sky Association of Thailand (RSAT), Service Workers In Group (SWING) Foundation and Sisters Foundation. Each participant will complete a short standardized questionnaire on risk behavior, including use of amphetamine-type stimulants (ATS) and other drugs. HIV testing will be done following usual HIV testing and counseling (HTC) guidelines. Stage 1 will collect data on ATS use in the community. The results from stage 1 will also be used to stratify participants for inclusion in stage 2 of the study.

Participants from the screening will be invited to participate in stage 2 of the study, which is the longitudinal cohort study. Recruitment will be stratified by HIV status and ATS use as listed in to ensure an adequate number of ATS users for data analysis. Participants in stage 2 will follow-up every 6 months for 18 months.

Stage 1 Stage one includes recruitment, the informed consent process, enrollment into the study, completion of the stage 1 questionnaire, and HIV counseling and testing. MSM/TG who present for routine HTC will be pre-screened for inclusion and exclusion criteria by the HTC counseling staff. MSM/TG who meet the inclusion criteria will be informed about the study and if interested will complete the informed consent process. After providing consent, participants will fill out the stage 1 questionnaire before receiving the HIV test result.

After the HIV test result is known to be positive or negative, the research staff will assign the participant to a study group (A,B,C,D) based on the HIV and ATS use status, as defined in section 3.2.3. If the study group has not yet filled to maximum size, then the participant will be offered participation in Stage 2 though another informed consent process. If the participant agrees, then the research staff will confirm contact information and will inform the participant that they will receive a reminder before the next visit in 6 months by their method of choice (telephone, SMS, email, Line, Facebook, etc).

If the study group has reached its maximum size, then the participant will be informed that their involvement in the study is finished and will be thanked for their contribution.

Stage 2 Stage 2 is the longitudinal follow-up of participants over 18 months. All study groups will follow the same schedule of follow-up visits one time every 6 months for 3 visits. At each visit, participants will complete a follow-up questionnaire and have a blood test. There will be no differences in procedures based on ATS use. Follow-up procedures will be divided by HIV status.

The four groups and sample sizes are:

1. Group A: HIV negative, non-ATS user (n=275)
2. Group B: HIV negative, ATS user (n=70)
3. Group C: HIV positive, non-ATS user (n=130)
4. Group D: HIV positive, ATS user (n=35)

Stage 1

Inclusion Criteria:

• Age 18 years or above
• Born biological male
• Self-identifies as MSM or transgender woman
• Thai citizen
• Resident in Bangkok or surrounding suburb
• Had sex with a male partner at least once in the previous 12 months
• Consents to participate in the study

Exclusion Criteria:

• Unable to perform any study procedures, or unable to commit to attend all study visits.
• Has a serious medical, psychological, or substance use problem that, in the opinion of the study staff, would prevent appropriate participation or adequate follow-up in the trial

Criteria: Stage 2

Inclusion Criteria:

• Must meet all of the criteria in stage 1, plus:
• Completed HIV test with result determined to be positive or negative
• Agrees to return for follow-up visits with testing per protocol every 6 months for 18 months
• Consents to participate in the study

Exclusion Criteria:

• Indeterminate HIV test result

The study population is Thai MSM or TGW who present for HIV counseling and testing at one of the participating sites.