This observational study aims to investigate medication adherence and drug-level monitoring of antiretroviral agents in a cohort of people living with HIV in Indonesia. The study is conducted in outpatients receiving tenofovir-based regimens in a university medical centre.

Optimal adherence is critical to achieve and sustain viral suppression. Currently, there is no gold standard measure of antiretroviral adherence and exposure in clinical practice. Recent studies have evaluated the use of emerging biological matrices such as dried blood spots, urine, and saliva as means of objective adherence measures. For drug-level monitoring, tenofovir is selected as a drug of interest and thus only people receiving tenofovir disoproxil fumarate-based regimens will be monitored. Some studies have reported that higher plasma trough concentrations of tenofovir were associated with renal toxicity. Therefore, this project aims to measure level of adherence and tenofovir concentrations in plasma and emerging matrices among people living with HIV in Indonesia. Primary outcome is adherence to ART that will be measured using multi methods, including self-report questionnaire, pill counting, electronic monitoring, and drug-level testing. Secondary outcomes include tenofovir concentrations in plasma, urine, saliva, and dried blood spots and clinical outcomes (viral load and CD4 count). Assays for measuring tenofovir concentrations will be developed using high-performance liquid chromatography-tandem mass spectrometry. Concentrations derived from dried blood spots, saliva, and urine will be compared to plasma concentrations. Pharmacokinetic models will be used to interpret drug-level monitoring. The association of adherence measures as well as drug concentrations and clinical outcomes will be examined.

Inclusion Criteria:

• Adults with HIV who have been receiving antiretroviral therapy containing tenofovir-based regimens for at least six months

Exclusion Criteria:

• Pregnant and breastfeeding women, people with kidney failure, undergoing hemodialysis or peritoneal dialysis, uncontrolled diabetes, uncontrolled hypertension, and hypersensitivity to tenofovir

All people living with HIV receiving antiretroviral therapy who regularly visit the HIV clinic at a university medical centre in Surabaya, Indonesia, during study period.

De-identified data will be available for analysing and reporting purposes and for other parties upon formal request to the principal investigators.