Drug-resistant tuberculosis treatment success predictors in Namibia

Drug-resistant tuberculosis (DR-TB) is a considerable barrier to ending TB globally by 2035. In most high TB-burden countries in the sub-Saharan region, drivers of DR-TB treatment success are unknown.

To determine predictors and patterns of treatment success rates (TSRs) in DR-TB in Namibia to inform strategies of national TB programmes.

A nationwide retrospective observational cohort study of a 6 year DR-TB database, 2014-19, was carried out. Independent predictors of successful treatment outcome in DR-TB were determined by multivariate logistic regression.

Of the 1494 DR-TB patients included, 56.3% (n = 841) were male, the mean (±SD) age was 35.6 ± 14.2 years, and 8.3% had TB/HIV coinfection. The overall TSR was 66.5% (n = 994) and it increased marginally between implementation of the second and third medium-term plans for TB and leprosy (MTP-II and MTP-III). Being female was associated with lower odds of treatment success [adjusted OR (aOR) = 0.6; 95% CI: 0.34-0.89; P = 0.015), as was a young age (under 5 years) (aOR = 0.1; 95% CI: 0.0007-0.421; P = 0.005) and ages of 5-14 years (aOR = 0.0; 95% CI: 0.002-0.269; P = 0.002). Namibian nationality also showed a reduced likelihood of treatment success (aOR = 0.3; 95% CI: 0.089-0.961; P = 0.043). Among clinical predictors, bilateral pulmonary forms were inversely associated with treatment success (aOR = 0.2; 95% CI: 0.057-0.498; P = 0.001). Conversely, baseline monoresistance was linked to an increased likelihood of treatment success (aOR = 7.6; 95% CI: 1.427-40.631; P = 0.018).

Whilst DR-TB TSRs improved, they are below the global target and vary by clinical and patient demographics. Targeted interventions for high-risk patients, including female patients, those aged under 15 years, locals and those with bilateral pulmonary disease using community-based approaches to boost adherence, alongside leveraging the skills of clinical pharmacists, should now be explored.