Abstract
Methods: This retrospective cohort study analysed 145 Isoniazid mono-resistant tuberculosis patients aged 18–65 years treated at Brewelskoof Hospital, Western Cape, South Africa, from 2009 to 2015. Demographic and clinical characteristics were obtained from the hospital’s tuberculosis registry. Data analyses used descriptive statistics, chi-square, analysis of variance, Kaplan–Meier survival, and Cox proportional hazards models to assess the time to sputum culture conversion and the intensive phase treatment outcomes, adjusting for relevant covariates. All statistical analyses were conducted using SAS 9.4 (SAS Institute, Cary, NC, USA).
Results: The median age of Isoniazid mono-resistant tuberculosis patients was 37 years, with an interquartile range (IQR) of 30–44, with 76 (52.41%) being males. After six months of treatment, 71 patients (48.97%) achieved sputum culture conversion, while 74 (51.03%) did not. The overall median time to sputum culture conversion was 55 days (IQR: 25–91), with significant variation across age groups (p=0.0074). The shortest time to sputum culture conversion was observed among patients aged 50–59 years (33.71±7.89 days). Overall, most Isoniazid mono-resistant tuberculosis patients (72.41%, 95%CI: 64.63–79.04) experienced unfavourable intensive phase treatment outcomes. Patients with unfavourable outcomes were 79% more likely to have delayed sputum culture conversion compared to those with favourable outcomes (HRR: 1.79, 95% CI: 1.07–2.98, p=0.0264). Conversely, patients who were 50-59 years were 4 times at risk of early conversion compared to individuals <20 years of age (HRR: 4.19, 95% CI: 1.13–15.61, p=0.0327).
Conclusion: Isoniazid mono-resistant tuberculosis patients in this cohort experienced prolonged time to sputum culture conversion and a high proportion of unfavourable intensive phase treatment outcomes. Delayed sputum culture conversion was strongly associated with poor treatment outcomes, highlighting the critical role isoniazid plays in drug-resistant tuberculosis therapy. Consequently, there is need for intensified monitoring and targeted interventions to improve early culture conversion and treatment success during the intensive phase treatment.