Time to sputum conversion in multidrug-resistant tuberculosis patients in Armenia: retrospective cohort study

OBJECTIVE: To characterize time to sputum conversion among patients with multidrug resistant tuberculosis who were enrolled into second-line tuberculosis treatment program; to identify risk factors for delayed sputum conversion. DESIGN: Retrospective cohort study designed to identify the factors associated with sputum conversion. Survival analysis was performed using Kaplan-Meier estimator to compute estimates for median time to sputum conversion and Cox proportional hazards model to compute hazard ratios (HR). RESULTS: Sputum conversion from positive to negative was observed in 134 out of 195 cases (69%). Among these who converted the median time to conversion was 3.7 months. Factors independently associated with time to sputum conversion in the proportional hazards model were: male sex (HR=0.51, 95% CI 0.32-0.81), ofloxacin-resistant tuberculosis (HR = 0.45, 95% CI 0.26-0.78) and first period of recruitment into second-line treatment (HR= 0.69, 95% CI 0.47-1.01). CONCLUSION: Time to sputum conversion in patients with multidrug-resistant tuberculosis in Armenia was 5.8 months (range 0.5-17.0 months). High level of ofloxacin resistance was the main reason for compromised response to treatment. Patients with a poor resistance profile and males should be targeted with more aggressive initial therapy.