User engagement in the tuberculosis treatment support tools intervention and its impact on treatment outcomes: A secondary analysis of a pragmatic trial

Digital adherence technologies (DATs) may improve health behaviors only when users engage, but links between engagement, user factors, and outcomes are unclear. TB Treatment Support Tools (TB-TST) is a DAT with a smartphone app connecting patients to treatment supporters and weekly drug metabolite testing. We evaluated TB-TST app engagement in a pragmatic randomized controlled trial and identified factors associated with adherence and treatment outcomes. Engagement was measured from app interactions by 277 participants over 180-days of TB treatment. Adherence was assessed via daily self-reports and weekly metabolite-test photo submissions. Participants could also message treatment supporters, report side effects, or request help. We modeled time to non-adherence (28 consecutive days without reporting) using survival analysis. Logistic regression tested associations of adherence and engagement with treatment outcomes. A latent engagement score was derived using confirmatory factor analysis (CFA) from medication reports, photo submissions, side-effect reports, messaging, and overall adherence. Participants submitted 24,902 medication reports, 2,926 messages, 2,465 photos, 1235 side effect reports, and 128 help requests. Adherence declined over time (78% at 60 days; 50% at 180 days). Non-adherence was more common among males, participants living at or below the poverty line, those without stable employment, and those treated at certain hospitals. Non-adherence was associated with lower odds of treatment success (OR 0.48, 95% CI: 0.22 - 0.94) and higher odds of loss to follow-up (OR 2.1, 95% CI: 1.03 - 4.7), adjusting for sex, age, education, income, and employment. Higher engagement scores were associated with higher odds of success (OR 2.2 times per standard deviation increase). Engagement with TB-TST was associated with improved TB treatment outcomes. Strategies to increase and sustain engagement, particularly among high-risk groups, may improve adherence and maximize DAT benefits.Author summary: Tuberculosis treatment lasts for many months, and interruption or incomplete therapy can lead to drug resistance and other poor outcomes. We studied how people used a smartphone-based support tool during tuberculosis self-administered treatment and whether more consistent use was linked to better outcomes. Digital tools can help patients take medications regularly, but they only work if people continue to use them over time. In our trial, the tool allowed participants to report when they took their daily dose, share a weekly photo of a simple test that indicates recent medication use, and communicate with a treatment supporter when they had questions, side effects, or needed help. We found that engagement with the tool decreased as treatment went on. People were more likely to stop reporting for long periods if they were men, had low income, lacked stable employment, or received care at non-referral hospitals. Importantly, people who stopped reporting were less likely to complete treatment successfully and more likely to be lost to follow-up. In contrast, people who used the tool more consistently had better treatment outcomes. These results suggest that digital support can strengthen tuberculosis care, but programs should invest in practical ways to keep people engaged, especially among groups at higher risk of falling behind.