Non-response to first-line anti-tuberculosis treatment in Sikkim, India: a risk-factor analysis study

Setting: Sikkim, India, has the highest proportion of tuberculosis (TB) patients on first-line anti-tuberculosis regimens with the outcome 'failure' or 'shifted to regimen for multidrug-resistant TB (MDR-TB)'. Objective: To assess the factors associated with non-response to treatment, i.e., 'failure' or 'shifted to MDR-TB regimen'. Methods: We conducted a retrospective cohort study using Revised National Tuberculosis Control Programme data of all TB patients registered in 2015 for first-line TB treatment. In addition, we interviewed 42 patients who had not responded to treatment to ascertain their current status. Results: Of 1508 patients enrolled for treatment, about 9% were classified as non-response to treatment. Patient factors associated with non-response were urban setting (adjusted odds ratio [aOR] 2.39, 95%CI 1.22-4.67), ethnicity (being an Indian tribal, aOR 1.73, 95%CI 1.17-2.57, Indian [other] aOR 1.83, 95%CI 1.29-2.60 compared to patients of Nepali origin) and those on retreatment (aOR 2.40, 95%CI 1.99-2.91). Of the patients interviewed, 28 (67%) had received treatment for drug-resistant TB. Conclusion: In Sikkim, one in 11 patients had not responded to first-line anti-tuberculosis treatment. Host-pathogen genetics and socio-behavioural studies may be required to understand the reasons for the differences in non-response, particularly among ethnic groups.