Determinants of drug-resistant tuberculosis: analysis of 11 countries

SETTING: Eleven countries/territories. OBJECTIVES: Global information on the determinants of drug-resistant tuberc ulosis (TB) based on representative data is not available. We therefore stu died the relationship between demographic characteristics, prior TB treatme nt, and human immunodeficiency virus (HIV) infection with anti-tuberculosis drug resistance. METHODS: Population-based representative data on new and previously treated patients with TB collected within an international drug resistance surveil lance network. RESULTS: Of 9615 patients, 8222 (85.5%) were new cases of TB and 1393 (14.5 %) were previously treated cases. Compared with new cases, previously treat ed cases were significantly more likely to have resistance to one (OR = 2.5 , 95%CI 2.1-3.0; P < 0.001), two (OR = 4.6, 95% CI 3.7-5.6; P < 0.001), thr ee (OR = 11.5, 95% CI 8.6-15.3; P < 0.001), and four (OR = 18.5, 95%CI 12.0 -28.5; P < 0.001) drugs. An approximately linear increase in the likelihood of having multidrug-resistant tuberculosis (MDR-TB) was observed as the to tal time (measured in months) of prior anti-tuberculosis treatment increase d (P < 0.001, <chi>(2) for trend). In multivariate analysis, prior TB treat ment for 6-11 months (OR = 7.6, 95%CI 2.6, 22.4; P < 0.001) and greater tha n or equal to 12 months (OR 13.7, 95%CI 4.5-41.6; P < 0.001), but not HIV p ositivity, was associated with MDR-TB. CONCLUSION: This study shows that prior but ineffective treatment is a stro ng predictor of drug resistance, and that HIV is not an independent risk fa ctor for MDR-TB. The association between length of treatment and drug resis tance may reflect longer treatment as a result of treatment failure in pati ents with drug resistance; it may also reflect irregular prior treatment fo r TB, leading to drug resistance.