Half finish preventive TB treatment despite high starts

Tuberculosis (TB) remains a leading danger for people living with HIV (PLWH), and giving TB preventive treatment (TPT) to people at risk is a key public health strategy. Trials have shown some TPT regimens work well, but less is known about how these drugs perform in everyday clinic settings where patients and programs vary. To fill that gap, Lucy Chimoyi and colleagues ran a two-year prospective cohort study from 2021 to 2023 in nine health facilities across Ethiopia, South Africa and Zimbabwe. They enrolled 2,095 PLWH receiving routine HIV care, collected socio-demographic and clinical data at the start, and then followed people as they were offered TPT while on antiretroviral therapy (ART). The team wanted to map the real-world “cascade” of TPT care — who is offered treatment, who starts it, who reports side effects, and who really completes a course — and to see how well TPT prevents new TB disease under routine program conditions.

The study tracked standard program actions and added extra measurements. During follow-up the researchers recorded TPT initiation, TPT-related side effects and completion. A subgroup of participants used digital boxes (evriMED1000) as a proxy measure for treatment completion; clinic records were also used. TB cases were identified from clinic records and by symptom-agnostic sputum testing using Xpert MTB/RIF assay and later MGIT culture at 12 and 24 months. Participants were mostly female (1,489; 71.1%) with a median age of 42 years [IQR: 35-50]. About 60% (1,312) were eligible for TPT and 1,110 (84.6%) were initiated on TPT within 60 days of ART start or at a refill visit. Regimens given included 3HP (n=625) and 6H/12H (n=487). Digital pillbox assessment showed only 55.4% (406/733) completed TPT. Symptoms compatible with side effects were more common with 3HP than with 6H/12H [190 (31.0%) vs. 51 (11.0%)]. The overall TB incidence rate was 1.27 (95% CI: 0.95–1.69) per 100 person-years, and completing TPT was associated with a lower rate of incident TB (adjusted incidence rate ratio aIRR: 0.39; 95% CI: 0.20–0.78, p=0.01). Over two years, 2.5% of participants developed TB disease.

These findings show clear strengths and weaknesses in real-world TPT programs. It is encouraging that most eligible patients were started on TPT, and that side effects were generally manageable and often self-limiting, but there were important losses at the final step: true completion. Clinic records that list a TPT completion date give an overly optimistic picture when compared with digital adherence data from the Medication Event Reminder Monitor (MERM)/evriMED1000 devices. The study suggests that even with only about half of people completing TPT as measured by the pillbox, those who did complete treatment saw a large reduction in new TB (about 61% lower). The authors argue for practical interventions to support patients through to completion, better tools to measure adherence and completion, and stronger program guidance so clinicians offer TPT to all eligible PLWH. In short, expanding starts is not enough — programs must help people finish their preventive treatment to gain the full public-health benefit, especially where resources are limited.