Objective  To analyze the situation and determinants of loss to follow-up among human immunodeficiency virus infection/acquired immunodeficiency syndrome (HIV/AIDS) patients under antireoviral treatment (ART) in four key counties of Liangshan prefecture, Sichuan province.

  Methods  With retrospective cohort study design, we enrolled all HIV/AIDS patients (aged ≥ 15 years) receiving ART during the period from 2005 through 2019 in 4 counties of Liangshan prefecture and conducted follow-ups of the patients untill the end of 2020. The patients′ information on diagnosis and ART were extracted from National HIV/AIDS Comprehensive Information Management System. Life table method was used to calculate the annual rate of loss to follow-up and accummulated follow-up rate; Cox proportion hazard regression method was adopted to explore risk factors of loss to follow-up.

  Results  The overall incidence rate of loss to follow-up was 14.82 per 100 person-years among all patients; the rate of loss to follow-up at the 1st, 3r, fifth, and the 10th year were 18%, 10%, 7%, and 10%, respectively. The multivariate Cox proportional hazard regression model showed that the patients with following characteristics were at a decreased risk of loss to follow-up: a) being female (versus male: adjusted hazard risk aHR = 0.83), b) aged ≥ 40 years (versus < 30 years: aHR = 0.93), c) being married or cohabitating (versus single: aHR = 0.85), d) being screened out from high risk populations (versus being diagnosed when attending medical services: aHR = 0.83), e) without co-infection of hepatitis C virus (HCV) or hepatitis B virus (HBV) (versus with HCV: aHR = 0.84 or with HBV: aHR = 0.92), and f) having the initiative ART during 2016 or 2017 (versus during 2018: aHR = 0.5) ; while, the patients having the initiative ART 1 – 5, 6 – 11, and ≥ 12 months after the confirmation of HIV infection were at an increased risk of loss to follow-up, with the aHR of 1.13, 1.18, and 1.34 compared to those having the initiative ART less than one month after the diagnosis. The patients′ risk of loss to follow-up differed by their living region and the patients in one of the four counties had the highest risk (aHR = 3.83) compared to the patients in the other counties.

  Conclusion  The incidence rate of loss to follow-up was relatively high in four counties of Liangshan prefecture; the rate decreased with the extension of ART treatment and the rate increased after 2018. Male gender, aged less than 30 years, being single, being diagnosed when attending medical service, with the co-infection of HCV or HBV, having the initiative ART more than one month after confirmed diagnosis were risk factors of loss to follow-up in the patients.