Factors associated with the development of drug resistant tuberculosis in Ethiopia

Abstract

PURPOSE: The purpose of this study was to assess factors associated with the development of drug resistant tuberculosis in Ethiopia. DESIGN: A quantitative case-control study was conducted to determine if there were any significant differences in prevalence of pre-defined factors between cases and controls. METHODS: Cases were patients with drug resistant tuberculosis who had a confirmed diagnosis by culture drug-susceptibility or gene expert tests. Successfully treated, tuberculosis symptom free patients who had been on first-line tuberculosis treatment and who were registered as cured or treatment completed were taken as controls. An equal number of cases (N=181) and controls (N=181) was selected using a systematic random sampling method and was used in the study. A structured questionnaire developed by the researcher was used to collect data. Odds ratio and multiple logistic regression were used to quantify the strength of association between dependent and independent variables. RESULTS: The development of drug resistant tuberculosis was significantly associated with two or more previous episodes of tuberculosis illness (adjusted odds ratio (AOR): 14.84; 95% CI 8.90 –24.75), previous first-line tuberculosis treatment not directly observed by a health worker for 7 to 8 weeks (AOR: 13.41; 95% CI 8.06 – 22.29) and previous first-line tuberculosis treatment outcome of failure (AOR: 39.19; 95% CI 12.05 -127.46). Interruption of first-line tuberculosis treatment for one day or more (AOR = 4.28; 95% CI 2.76 – 6.64) and history of treatment in the first-line tuberculosis treatment category for previously treated patients (AOR: 3.70; 95% CI 2.40 – 5.72) were also significantly associated with the development of drug resistant tuberculosis in the current study. CONCLUSION: Patients with a history of previous first-line tuberculosis treatment, patients who interrupted previous first-line tuberculosis treatment and patients with previous first-line tuberculosis treatment outcome of failure were at high risk of developing drug resistant tuberculosis. Therefore, the full course of first-line tuberculosis treatment should be given, following the Directly Observed Treatment (DOT) guide. Patients with recurrent tuberculosis and unfavourable first-line tuberculosis treatment outcome should be tested for drug susceptibility.