Differences in HIV testing may determine the first pillar of the HIV care continuum in a cross-border setting.

INTRODUCTION: In border regions like the EuRegio Meuse-Rhine (EMR), mobility does not stop at the border. HIV risk may therefore not only be determined by within-country factors but also by between-country differences. We explored between-country differences in HIV indicators in the EMR using two complementary data-driven approaches. METHODS: First, we used 2019-2021 surveillance data from the German Robert Koch Institute, the Belgian Health Institute Sciensano and the Dutch HIV Monitoring Foundation to report on the EMR-specific 95-95-95 goals. Second, we used the cross-sectional EMIS-2017 survey, including (trans)men who have sex with men (MSM), to report on determinants of HIV testing in the EMR. We employed multilevel multinomial regression modelling to identify sociodemographic factors associated with recent (<1 year), non-recent (≥1 year) and never testing for HIV, with a random effect for between-country effects. RESULTS: Based on 2021 surveillance data, the estimated number of individuals with HIV is 24 895, with 2236 individuals undiagnosed (9%). Countries differ most on the first pillar of the 95-95-95 goals: 95-93-96 in the Dutch, 90-98-96 in the German and 96-94-97 in the Belgian EMR-region, respectively. In EMIS-2017, half of MSM (n = 1335/2669) tested recently, 26% tested not-recently (n = 693) and 24% (n = 641) never tested for HIV; with 8% of HIV-testing variance explained by between-country differences. Non-recent and never-testing were both associated with socio-demographic factors, suggesting that some key populations (e.g., with transgender identity) and lack of resources determined differences in HIV testing. CONCLUSION: Targeted approaches to address regional and socio-demographic differences are urgently needed, especially to tackle HIV-testing barriers and reach individuals undiagnosed.