Background: About 40 000 cases of extensively drug-resistant tuberculosis emerge worldwide annually, but the predictors of extensive drug resistance are unclear.
Objective: To identify risk factors for extensively drug-resistant tuberculosis and multidrug-resistant but non-extensively drug-resistant tuberculosis in patients with culture-confirmed pulmonary tuberculosis.
Design: Cross-sectional, countrywide study.
Setting: Estonia, a country with 1 of the world's highest rates of extensively drug-resistant and multidrug-resistant tuberculosis.
Patients: All patients with culture-confirmed pulmonary tuberculosis with clinical or radiologic evidence of active disease detected from January 2003 to December 2005.
Measurements: Risk determinants from patients' demographic characteristics, socioeconomic variables, and tuberculosis-related data or HIV status.
Results: Of 1163 patients, 60 (5.2%) had extensively drug-resistant tuberculosis and 196 (16.9%) had multidrug-resistant but non-extensively drug-resistant tuberculosis. Previous antituberculosis treatment (adjusted odds ratio [OR], 10.54 [95% CI, 5.97 to 18.62]), HIV infection (OR, 3.12 [CI, 1.31 to 7.41]), homelessness (OR, 2.73 [CI, 1.15 to 6.48]), and alcohol abuse (OR, 1.98 [CI, 1.08 to 3.64]) increased risk for extensive drug resistance. Previous treatment (OR, 4.11 [CI, 2.77 to 6.08]) and age 24 years or younger (OR, 2.57 [CI, 1.09 to 6.06]), 25 to 44 years (OR, 2.64 [CI, 1.35 to 5.16]), and 45 to 64 years (OR, 2.06 [CI, 1.06 to 3.99]) were determinants of multidrug resistance. In patients age 24 years or younger, female sex (OR, 6.23 [CI, 1.02 to 37.99]) and birth outside of Estonia (OR, 82.04 [CI, 3.46 to 1945.47]) increased risk for multidrug resistance.
Limitation: Patients' comorbid conditions and drug abuse history were not incorporated into analyses because of inconsistent source data.
Conclusion: Previous treatment is a common risk factor for extensively drug-resistant and multidrug-resistant tuberculosis. Reducing relapses; screening persons younger than 65 years and immigrants; and combating against HIV infection, alcoholism, and homelessness are key issues for decreasing the spread of highly drug-resistant tuberculosis.