Tuberculosis (TB) is second only to the coronavirus infectious disease 2019 (COVID-19) as a single-species cause of adult infectious death worldwide1. Nearly four of the 10.6 million people estimated to develop TB each year are not diagnosed or treated. Moreover, an estimated 1.6 million people died of TB in 2021, with the large gap between TB diagnosis and treatment being a major contributor to mortality1-4. The World Health Organisation (WHO) has identified 30 high TB burden countries (TB burden, HIV-associated TB burden, multi-drug resistant/rifampicin resistant-TB) that are predominately low- or low-to-middle income, and together accounted for 86-90% of the estimated global TB incidence in 20191. Within these countries, and globally, TB disproportionally affects the poor, and most of the 'missed' cases occur among populations with limited access to healthcare (men, people living with HIV, residents of rural and remote settings and informal urban settlements and displaced populations5 and in children6.

The WHO End TB Strategy calls for a 90% reduction in TB deaths by 2030 compared to 2015, an 80% reduction in estimated TB incidence, and elimination of household catastrophic costs due to TB. Unfortunately, the 2021 WHO Global TB Report shows that we are very far from achieving these targets, and they will likely not be met without a step-change in efforts to improve early diagnosis and treatment of TB. Moreover, the COVID-19 pandemic severely disrupted TB diagnosis and treatment programs, hindering efforts to eliminate TB as a public health issue, and the ramifications of the pandemic are likely to be experienced by fragile health systems for many years7. New approaches to facilitate access to same-day, same-setting diagnosis and treatment of TB are urgently required.

TB detection in adults is mainly dependent upon passive case finding (PCF), requiring individuals to visit health facilities, be asked by health workers whether they have symptoms consistent with TB, and subsequently tested for TB. Only some countries use active case finding (ACF) and intensified case funding (ICF) as a complementary measure 8,9. However, this approach has considerable limitations. Exit interviews at clinics and simulated patient studies demonstrate that clinicians rarely ask about TB symptoms10-12, and even when patients volunteer symptoms, sputum testing is infrequently requested, and patients are often unable to produce sputum10. Thus, PCF is insufficient to identify most people with TB and needs to be supplemented with other approaches, such as intensified case finding in health facilities and ACF, which allows detection of people with infectious TB (and potentially asymptomatic TB; an estimated 50% of prevalent community cases14), speeding up diagnosis and linkage to treatment, and potentially reducing transmission. The location where people with presumptive TB are tested and the timeliness of diagnosis are also important. Approaches that rely on sputum transport networks or referral of patients to centralized laboratories often result in diagnostic delays and poor linkage to treatment, while local testing has been associated with increased numbers detected and confirmed and improved linkage to treatment15. TB diagnosis is also particularly challenging for well-defined key and vulnerable populations, including: people living in communities with very high HIV prevalence16; those living in informal urban settlements with poor access to health facilities and marginalized communities, such as refugees and nomadic groups; and in children.

Overall, for this study, countries have been selected to provide a broad representation from World Bank country development groups, global regions, covering South-East Asia, Africa, and the Americas, with a combined population of 780 million people. We have included countries with a high TB burden in the general population (Bangladesh, Brazil, Kenya, Nigeria); countries with a high burden of HIV-associated TB (Brazil, Cameroon, Kenya, Malawi, Nigeria); and countries with a high burden of drug resistant TB (Bangladesh, Nigeria, Vietnam)1. Data across partner countries, have shown that TB-affected households experienced health-related costs reaching 50% of their annual household income in Sub Saharan African countries such as Nigeria, Cameroon, Malawi and Kenya17-19. Given these findings, WHO's End TB Strategy included the goal of zero TB-affected families incurring catastrophic costs. These are defined as 20% of annual household income lost due to an episode of TB. Countries that have conducted formal patient cost surveys employing WHO tools and definitions such as Vietnam have measured catastrophic cost incurrence of 63% and 98% among drug susceptible (DS) DS-TB and multidrug resistant (MDR) MDR-TB households, respectively20. Thus, as diagnostics can play a critical role in optimizing the patient pathway, better diagnostic tools and algorithms may also positively impact performance against the End TB Strategy's socioeconomic indicator. In this project we will aim to demonstrate that combinations of current and newer TB tests can facilitate TB diagnostic testing in locations where it is not currently available; that the optimized use of tests at the point of need increases the proportion of people correctly diagnosed, increases access to TB treatment, and potentially reduces TB mortality and transmission.

The project will focus on key and vulnerable populations including in settings where TB diagnostic testing is not normally performed, and people are diagnosed clinically due to limited access to laboratory facilities. In Phase 1 we will identify new combinations of tests to provide same-day, same-setting diagnosis, and assess the feasibility of scaling-up and subsequent linkage to TB care that will be formally assessed in Phase 2 of the research.