Community-based active case finding for tuberculosis [TB0118]

Despite advancements in TB diagnostics, approximately 4 million patients—nearly 40%—remain undiagnosed or unreported globally. The majority of these individuals reside in periurban informal settlements in large cities across Africa and Asia. Detecting and treating these "missing" patients is critical for TB control, as they act as potential reservoirs for the transmission of drug-sensitive and drug-resistant strains of Mycobacterium tuberculosis.

Modeling studies suggest that reducing TB transmission, disease burden, and mortality requires community-based active case finding (ACF)—where healthcare workers proactively seek, identify, and test patients for TB in the community—rather than passive case finding, which relies on patients self-presenting at healthcare facilities. Passive case finding typically identifies cases only after significant transmission has already occurred.

Several ACF approaches are used in high-prevalence settings, including:

• Targeted screening of high-risk groups, such as close contacts of TB index cases.
• Community-based door-to-door screening.
• Community-based screening using mobile units or clinics.

Door-to-door ACF, utilizing laboratory-based molecular tools like the Cepheid GeneXpert system, has demonstrated a positive impact on disease burden in the wider community. However, this method is labor-intensive and often cost-prohibitive in resource-limited settings. Studies conducted before the widespread availability of automated molecular diagnostic tools showed that both door-to-door and mobile unit-based screening strategies effectively reduced disease burden at the community level, with mobile units proving more efficient.

An innovative ACF strategy involving a mini-mobile clinic has shown promise. This scalable intervention uses a low-cost minivan and a portable, battery-operated Xpert system (the XACT model). It was not only feasible but also successful in detecting the majority of infectious TB cases, including those who did not self-report to healthcare facilities. Notably:

• The number of at-risk individuals (e.g., those with TB symptoms or HIV-positive) needing to be screened to detect one active TB case was 18 for Xpert compared to 99 for smear microscopy.
• Point-of-care (POC) Xpert detected a higher proportion of culture-positive TB patients and significantly reduced the time to treatment initiation, compared to same-day smear microscopy conducted at nearby microscopy centers (within a 5-km radius).

Overall, mobile, point-of-care strategies like the XACT model represent a practical and impactful solution to addressing the global burden of undiagnosed TB.

Source: Esmail, A., Randall, P., Oelofse, S. et al. Comparison of two diagnostic intervention packages for community-based active case finding for tuberculosis: an open-label randomized controlled trial. Nat Med 29, 1009–1016 (2023). https://doi.org/10.1038/s41591-023-02247-1