Prevalence and reasons of loss to follow-up in HIV clinics: a systematic review of current evidence

Introduction: Loss to follow-up (LTFU) slows the progress in reaching the goals of human immunodefi-ciency virus (HIV) prevention and treatment. Therefore, it is important to understand the causes behind this phenomena. Herein, we aimed to systematically review the prevalence of LTFU among people living with HIV and the reasons behind this event.Material and methods: A systematic search was conducted with key words applied in online databases, including PubMed, Web of Science, Scopus, UpToDate, and Science Direct, from January 2015 to March 2021. Most relevant papers were retrieved and screened in two phases against inclusion criteria, based on their title/abstract and their full texts, and eligible records were included in the review. Results: In this systematic review, 54 studies were included. Unfavorable socio-demographic and sup-portive status, distance to facility, age, gender, challenges related to antiretroviral therapy initiation and its' side effects, and CD4+ counts were among the most common reasons cited for LTFU in HIV clinics.Conclusions: LTFU remains a major factor halting the progress in the prevention and treatment of HIV. Great efforts are still needed to address this issue, especially in populations and regions with higher LTFU incidence. Accessibility of receiving care should be increased to encourage patients to continue their treatments. Upcoming follow-up studies are needed to re-evaluate the progress and to report future challenges and limitations.