Systematic screening for active tuberculosis: rationale, definitions and key considerations [State of the art series. Active case finding/screening. Number 1 in the series]

The impact of current interventions to improve early detection of tuberculosis (TB) seems to have been saturated. Case detection trends have stagnated. TB incidence is falling in most settings worldwide, but the rate of decline is far lower than expected. There is growing evidence from national TB prevalence surveys and other research of a large pool of undetected TB in the community. Intensified efforts to further break down access barriers and scale up new and rapid diagnostic tools are likely to improve the situation. However, will these be enough? Or do we also need to reach out more towards people who do not actively seek care with well-recognisable TB symptoms? There have recently been calls to revisit TB screening, particularly in high-risk groups. The World Health Organization (WHO) recommends screening for TB in people with human immunodeficiency virus infection and in close TB contacts. Should other risk groups also be screened systematically? Could mass, community-wide screening, which the WHO has discouraged over the past four decades, be of benefit in some situations? If so, what screening tools and approaches should be used? The WHO is in the process of seeking answers to these questions and developing guidelines on systematic screening for active TB. In this article, we present the rationale, definitions and key considerations underpinning this process.