Evaluation of a combined tuberculosis case-finding, treatment and prevention strategy in Thailand: protocol for a pragmatic phase IV stepped-wedge cluster-randomised trial, the CaPThai study

Background To end the tuberculosis (TB) epidemic, the WHO recommends implementing active case-finding to increase TB detection, as well as the provision of TB preventive treatment (TPT) in contacts of people with TB. However, the scale-up of both strategies remains limited in high TB-burden countries such as Thailand. Despite the country's highly decentralised healthcare system, significant inequalities remain in access to care, particularly in vulnerable populations. We designed an intervention study investigating the effectiveness and feasibility of a novel strategy combining active case-finding and the implementation of short-course TPT in households of newly diagnosed adults with TB in Thailand. Methods This is a pragmatic phase IV stepped-wedge cluster-randomised trial conducted in 20 provincial hospitals (clusters). The study population comprises household members who were exposed within the last 3 months to adults with newly detected bacteriologically confirmed TB. The intervention combines an educational video to the index TB case, provision of an invitation card to household contacts for free TB screening at the facility, with a transport voucher, and support from village or urban health volunteers. Household contacts without active TB are offered TPT regimens according to age: 1-month rifapentine-isoniazid (1HP), 3-month rifapentine-isoniazid (3HP) or 3-month rifampicin-isoniazid (3HR). In the control phase, TB staff implement the current standard of care, including verbal information to persons newly diagnosed with TB on the need to screen their household contacts and provision of standard TPT. Hospitals shift from the control to the intervention phase every 3 months in four randomised sequences until all clusters apply the intervention. Generalised linear mixed models will be used to compare the intervention outcomes versus the standard of care, controlling for clustering and confounding by time. Discussion Active case-finding and systematic TPT in at-risk populations is currently limited in Thailand. This protocol incorporates pragmatic design features with a participant-centred approach to assess the effectiveness, feasibility and acceptability of a combined strategy including systematic screening of household contacts, active case-finding and TPT provision. If successful, this strategy will likely contribute to TB elimination in Thailand and beyond. Trial registration The study is registered at ClinicalTrials.gov NCT05581212 on April 3rd, 2024, and is currently recruiting.