RESUMEN
INTRODUCTION: People living with HIV who are lost to follow-up have a greater risk of health deterioration, mortality, and community transmission. OBJECTIVE: Our aim was to analyse both how rates of loss to follow-up (LTFU) changed between 2006 and 2020 and how the COVID-19 pandemic affected these rates in the PISCIS cohort study of Catalonia and the Balearic Islands. METHODS: We analysed socio-demographic and clinical characteristics of LTFU yearly and with adjusted odds ratios to assess the impact of these determinants on LTFU in 2020 (the year of COVID-19). We used latent class analysis to categorize classes of LTFU based on their socio-demographic and clinical characteristics at each year. RESULTS: In total, 16.7% of the cohort were lost to follow-up at any time in the 15 years (n = 19 417). Of people living with HIV who were receiving follow-up, 81.5% were male and 19.5% were female; of those who were lost to follow-up, 79.6% and 20.4% were male and female, respectively (p < 0.001). Although rates of LTFU increased during COVID-19 (1.11% vs. 0.86%, p = 0.024), socio-demographic and clinical factors were similar. Eight classes of people living with HIV who were lost to follow-up were identified: six for men and two for women. Classes of men (n = 3) differed in terms of their country of birth, viral load (VL), and antiretroviral therapy (ART); classes of people who inject drugs (n = 2) differed in terms of VL, AIDS diagnosis, and ART. Changes in rates of LTFU included higher CD4 cell count and undetectable VL. CONCLUSIONS: The socio-demographic and clinical characteristics of people living with HIV changed over time. Although the circumstances of the COVID-19 pandemic increased the rates of LTFU, the characteristics of these people were similar. Epidemiological trends among people who were lost to follow-up can be used to prevent new losses of care and to reduce barriers to achieve Joint United Nations Programme on HIV/AIDS 95-95-95 targets.