Breakthrough TB among people living with HIV on TB preventive therapy

BACKGROUND: Zambia has an estimated TB incidence of 319/100,000 population and a HIV prevalence of 11.1%. In 2020, only 49% of new people living with HIV (PLHIV) received TB preventive therapy (TPT) in Zambia. Misconceptions about the reliability of symptom screening and drug
 resistance among people who develop TB while on TPT are barriers to TPT scale-up. We determined the incidence and predictors of breakthrough TB during TPT among PLHIV in Zambia.METHOD: This was a retrospective analysis of routine TPT programme data among PLHIV collected between
 October 2016 and October 2019 from select primary health facilities in Zambia.RESULTS: Of 48,581 PLHIV enrolled on TPT, 130 (0.3%) developed breakthrough TB during TPT. Of the 130, 90 client records were accessed. The median age of the breakthrough TB cases was 35 years; 68% were
 males. Overall, 96% of the breakthrough TB cases had been on antiretroviral therapy (ART) for 3 months; 24% were symptomatic at the beginning of TPT, 22% were asymptomatic and others had missing data. Of the 130 breakthrough TB cases, 79% developed TB in the first month after TPT initiation.
 The median time to TB diagnosis was 10 days (IQR 4–16).CONCLUSION: Breakthrough TB during TPT is rare among PHLIV on ART, and very rare after the first month of TPT initiation. It should therefore not be a barrier to TPT scale-up.