Optimizing Pan-Viral Screening and Linkage to Treatment and Vaccination Among GBMSM and Trans Women in Spain, Including PrEP Users and Those Awaiting Access: An Online Self-Sampling Pilot Study

Background: The World Health Organization (WHO) aims to eliminate viral hepatitis as a public health threat by 2030, targeting significant reductions in incidence and mortality for hepatitis B and C. Despite these goals, hepatitis C virus (HCV) transmission and acute infection rates have risen among gay, bisexual, and other men who have sex with men (GBMSM), especially those with HIV. Chemsex, particularly involving drug injection, is a notable risk factor. Hepatitis B virus (HBV) also poses a significant public health challenge, with chronic hepatitis B leading to severe liver damage in a significant portion of those infected. Hepatitis D virus (HDV), which requires HBV co-infection, adds further complexity to the management of viral hepatitis. Integrating evidence-based interventions for HIV and STI prevention, including effective screening and linkage to care, is urgently needed.

Objectives: This study aims to design, implement, and evaluate an online self-sampling testing strategy to enhance pan-viral testing (HBV, HCV, HDV, HIV) and improve linkage to care among GBMSM and transgender women (TW) in Spain. Specific objectives include:

1. Designing and implementing an online self-sampling pilot intervention for HBV, HIV, and viremic HCV detection using dried blood spot (DBS) samples, and following up on positive HBV cases for HDV co-infection.
2. Analyzing the intervention's effectiveness in reaching and identifying undiagnosed infections among GBMSM and TW not recently tested for HIV and viral hepatitis.
3. Identifying individuals who have not vaccine-induced protective levels against HBV and linking them to vaccination (or revaccination) services.
4. Evaluating the intervention's acceptability among GBMSM and TW inSpain.
5. To identify the number of individuals with HIV infection while they are waiting PrEP (missed opportunities to prevent HIV infection) A secondary objective is to validate DBS samples for detecting HBV surface antigen (HBsAg).

Methods: This non-randomized single-arm prospective and national study will recruit adult GBMSM and TW through PrEP services, social media, gay dating apps, NGOs, and outreach interventions. Participants will complete a risk assessment using the HCV-MOSAIC algorithm, and eligible individuals will receive a self-sampling kit for HBV, HCV, and HIV testing. The kits will include instructions, a lancet, a Whatman card for DBS collection, and a pre-paid return envelope. Samples will be analyzed by a reference laboratory for HBsAg, HIV antibodies, and HCV RNA. Participants will receive their results online, with follow-up for those testing positive to confirm diagnoses and linkage to care. Those who test positive for HBsAg will be further tested for other tests, including HBV DNA, and HDV infection.

Expected Outcomes: The study will estimate HBV, HDV, HCV, and HIV prevalences, assess linkage to care and treatment outcomes, and evaluate the acceptability and usability of the self-sampling intervention. Additionally, the validation of DBS for HBsAg detection will provide crucial data for future screening strategies.