Free Content Impact of second-line drug resistance on tuberculosis treatment outcomes in the United States: MDR-TB is bad enough

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SETTING: The worldwide emergence of extensively drug-resistant tuberculosis (TB) has focused attention on treatment with second-line drugs (SLDs).

OBJECTIVE: To determine the impact on outcomes of resistance to individual SLDs, we analyzed successful treatment completion and death among drug-resistant TB cases in the US national TB surveillance system, 1993–2007 (N = 195 518).

DESIGN: We defined four combinations of first-line drug (FLD) resistance based on isoniazid (INH) and rifamycin, and three patterns of SLD resistance: fluoroquinolones, injectable SLDs and other oral SLDs. We compared treatment outcomes of cases by FLD resistance, with and without each pattern of SLD resistance.

RESULTS: In all but one instance, cases with FLD resistance but no SLD resistance had better outcomes than cases with SLD resistance. Rifamycin resistance, alone or with INH, resulted in a greater decline in treatment completion and greater increase in deaths than resistance to SLDs. Among patients with multidrug-resistant TB, additional resistance to injectable SLDs was statistically significant. Outcomes were better for human immunodeficiency virus (HIV) negative than HIV-positive cases for all resistance patterns, but improved among HIV-infected cases after 1998, when highly active antiretroviral treatment became widely available.

CONCLUSION: These results suggest that the effect of rifamycin resistance may outweigh the more modest effects of resistance to specific SLDs.

Keywords: drug-resistant TB; second-line resistance; treatment outcomes

Document Type: Research Article


Affiliations: Division of Tuberculosis Elimination, US Centers for Disease Control and Prevention, Atlanta, Georgia, USA

Publication date: October 1, 2012

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  • The International Journal of Tuberculosis and Lung Disease publishes articles on all aspects of lung health, including public health-related issues such as training programmes, cost-benefit analysis, legislation, epidemiology, intervention studies and health systems research. The IJTLD is dedicated to the continuing education of physicians and health personnel and the dissemination of information on tuberculosis and lung health world-wide.

    Certain IJTLD articles are selected for translation into French, Spanish, Chinese or Russian. They are available on the Union website

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