What's new in TB diagnosis? A spotlight on active case-finding.

Tuberculosis (TB) remains the deadliest infectious disease globally, with gaps in case detection hindering its control. Active case-finding (ACF) comprises active screening of at-risk populations, including asymptomatic individuals, who constitute over half of TB prevalence in high-burden areas and who may contribute to community-based transmission. Common ACF models in community settings include door- to-door screening or mobile, vehicle-based screening using chest X-ray and/or molecular testing modalities. Other forms include healthcare facility-based screening and mass screening in congregate settings. The World Health Organization recommends ACF for communities with a TB prevalence of ≥0.5%, and its implementation is most effective in TB 'hot spots'. ACF can also be focused on specific at-risk groups such as household contacts and people living with HIV. Despite resource and logistical challenges, community-based ACF trials have demonstrated significant reductions in TB prevalence with repeated rounds of screening. In practice, however, community-based ACF is rarely undertaken by TB programmes in endemic countries, owing to limited funding ('willingness to pay') and a lack of context-specific, evidence-based operational guidance on ACF implementation. Therefore, the real-world effect of ACF will likely depend on implementation intensity, the use of scalable and accurate screening and diagnostic tools, and engagement with communities and health systems.