A population-based study of risk factors for drug-resistant TB in British Columbia.

SETTING

Provincial tuberculosis (TB) services, British Columbia, Canada.

OBJECTIVE

To investigate risk factors associated with resistance to anti-tuberculosis drugs in British Columbia and to determine if there are differences in risk factor characteristics among different resistance categories.

DESIGN

Using population-based data from provincial TB services, all patients with positive culture for Mycobacterium tuberculosis from 1990 to 2001 were identified and included in the study. Logistic regression analyses were performed to assess risk factors for drug resistance.

RESULTS

Among 3041 eligible TB cases, 295 (10%) were found to be drug-resistant. Significant risk factors for resistance were younger age, foreign birth, ethnicity, reactivated TB and place of initial diagnosis. Foreign-born subjects (OR 3.18, 95%CI 2.26-4.49) were three times more likely to present with resistance than Canadian-born subjects. Among ethnic groups, Chinese (OR 2.32, 95%CI 1.51-3.57), South-East Asian (OR 2.92, 95%CI 1.88-4.52) and Other Asian subjects (OR 4.40, 95%CI 2.77-7.01) were 2-4 times more likely to present with resistance than Caucasians. Reactivated cases (OR 2.69, 95%CI 1.91-3.77) were three times as likely to have resistance as new cases.

CONCLUSION

These results document and quantify the risk of drug-resistant disease in a large population-based cohort, and highlight patient groups who should be identified as at risk for drug-resistant disease in the industrialised world.