Factors Associated With Loss to Follow-Up Among People Living With HIV in a National Tertiary Care Hospital: Protocol and Baseline Analysis of a Prospective Cohort Study.

Background: Advances in antiretroviral therapy (ART) have significantly improved the life expectancy of people living with HIV. However, maintaining retention in care-defined as ongoing engagement with medical services from diagnosis through regular follow-up-is essential for optimal clinical outcomes. Loss to follow-up (LTFU), commonly defined as the absence of ART prescription refills or medical visits for more than 90 days, has been associated with increased mortality, treatment failure, and continued community transmission. Although multiple individual and structural factors have been linked to LTFU, evidence from the Mexican context remains limited. Objective: This protocol describes a prospective cohort study designed to identify factors associated with LTFU among recently diagnosed people living with HIV in Mexico. Methods: We conducted a prospective cohort study at a national tertiary care hospital in Guadalajara, Jalisco, Mexico. Eligible participants were adults (≥18 years) who had initiated ART within 6 months prior to enrollment. Data on sociodemographic, clinical, HIV-related, and psychosocial variables were obtained from electronic medical records, pharmacy dispensing logs, and validated questionnaires (Simplified Medication Adherence Questionnaire, Berger HIV Stigma Scale, and the Medical Outcomes Study HIV Health Survey). The primary outcome is LTFU, defined as ≥90 consecutive days without a medical visit or ART refill, ascertained through institutional records and national ART dispensation systems. Participants will be followed for 24 months. Planned analyses include descriptive statistics, Kaplan-Meier curves for time to LTFU, and multivariable Cox and logistic regression models to identify factors independently associated with disengagement from care. Results: Recruitment took place between December 2023 and March 2024, yielding 164 enrolled participants who completed all baseline assessments. The 24-month follow-up period for this cohort extends from April 2024 through March 2026, with primary analyses and dissemination of results planned for the second half of 2026. Baseline data indicate that the cohort is characterized by substantial socioeconomic vulnerability, a high prevalence of late presentation, and notable levels of perceived stigma and reduced health-related quality of life. Conclusions: This protocol outlines a prospective cohort study to evaluate factors associated with LTFU among people living with HIV in a Mexican tertiary care setting. The baseline findings highlight substantial socioeconomic, clinical, and psychosocial vulnerabilities that may compromise long-term retention in care. The longitudinal follow-up of this cohort will provide context-specific evidence to inform targeted interventions aimed at improving engagement in care and reducing LTFU in similar populations.