Conditional cash transfers to incentivize tuberculosis screening: Description of a novel strategy for contact investigation in rural South Africa.

Background Providing incentives to screen close contacts for tuberculosis (TB) is an alternative to traditional household-based contact investigation. We aimed to characterize patients and contexts for which this incentive-based strategy might be preferred. Methods This is a secondary analysis of a cluster randomized trial of TB contact investigation in Limpopo District, South Africa, conducted between 2016-2020. Twenty-eight clinics were randomly allocated to household-based versus incentive-based contact investigation. In the incentive-based arm, index participants and contacts received transport reimbursement and incentives for TB screening and microbiological diagnosis of contacts. We estimated the absolute difference in mean number of contacts per index participant with household-based versus incentive-based contact investigation, overall and within sub-groups of index participants. Results A total of 3776 contacts (1903 in the incentive-based and 1873 in the household-based arm) were referred by 2501 index participants. A higher proportion of contacts in the incentive-based than household-based arm were adults (72% vs 59%) and reported chronic TB symptoms (25% vs 16%) or ever smoking (23% vs 11%). Index participants who walked or bicycled to clinic referred 1.03 more contacts per index (95%CI:0.48-1.57) through incentive-based than household-based investigation. Index participants living with >5 household members referred 0.48 more contacts per index (95%CI:0.03-0.94) through household-based than incentive-based investigation. Conclusions Relative to household-based contact investigation, incentive-based investigation identifies contacts who appear to be at higher risk for active TB. Incentive-based investigation may be more appropriate for index participants who can easily access the clinic, whereas household-based investigation should be prioritized for patients with large households.