Extensively Drug-Resistant Tuberculosis in the United States, 1993-2007

Context Worldwide emergence of extensively drug-resistant tuberculosis (XDR-TB) has raised global public health concern, given the limited therapy options and high mortality. Objectives To describe the epidemiology of XDR-TB in the United States and to identify unique characteristics of XDR- TB cases compared with multidrug- resistant TB (MDR-TB) and drug- susceptible TB cases. Design, Setting, and Patients Descriptive analysis of US TB cases reported from 1993 to 2007. Extensively drug- resistant TB was defined as resistance to isoniazid, a rifamycin, a fluoroquinolone, and at least 1 of amikacin, kanamycin, or capreomycin based on drug susceptibility test results from initial and follow- up specimens. Main Outcome Measures Extensively drug- resistant TB case counts and trends, risk factors for XDR- TB, and overall survival. Results A total of 83 cases of XDR- TB were reported in the United States from 1993 to 2007. The number of XDR- TB cases declined from 18 ( 0.07% of 25 107 TB cases) in 1993 to 2 ( 0.02% of 13 293 TB cases) in 2007, reported to date. Among those with known human immunodeficiency virus ( HIV) test results, 31 ( 53%) were HIV- positive. Compared with MDR- TB cases, XDR- TB cases were more likely to have disseminated TB disease ( prevalence ratio [ PR], 2.06; 95% confidence interval [ CI], 1.19- 3.58), less likely to convert to a negative sputum culture ( PR, 0.55; 95% CI, 0.33-0.94), and had a prolonged infectious period ( median time to culture conversion, 183 days vs 93 days for MDR- TB; P <. 001). Twenty- six XDR- TB cases ( 35%) died during treatment, of whom 21 ( 81%) were known to be HIV- infected. Mortality was higher among XDR- TB cases than among MDR- TB cases ( PR, 1.82; 95% CI, 1.10- 3.02) and drug- susceptible TB cases ( PR, 6.10; 95% CI, 3.65- 10.20). Conclusion Although the number of US XDR- TB cases has declined since 1993, coinciding with improved TB and HIV/ AIDS control, cases continue to be reported each year.