Increasing outpatient fluoroquinolone exposure before tuberculosis diagnosis and impact on culture-negative disease

Background: Fluoroquinolones are widely used to treat routine bacterial infections, but they are also potential first-line antituberculosis agents. Empirical fluoroquinolone therapy can delay the diagnosis of tuberculosis and cause resistance in Mycobacterium tuberculosis. Rates of fluoroquinolone exposure before tuberculosis diagnosis and the impact of fluoroquinolones on culture-negative tuberculosis have not been previously reported. Methods: All newly diagnosed tuberculosis cases reported to the Tennessee Department of Health between January 1, 2000, and December 31, 2004, were cross-matched with the TennCare (Medicaid) pharmacy database to assess for outpatient fluoroquinolone use in the 12 months before tuberculosis diagnosis. Results: Of 1562 tuberculosis cases reported, 1055 occurred in TennCare participants; of these 1055 TennCare patients, 507 were enrolled in TennCare more than 300 days during the year before tuberculosis diagnosis. Of the 507 patients, 119 (23%) received a fluoroquinolone before tuberculosis diagnosis. The proportion of fluoroquinolone-exposed patients increased from 9% in 2000 to 41% in 2004 (chi 2 test for trend P <.001). In multivariate logistic regression analysis, factors associated with fluoroquinolone exposure were older age (odds ratio [OR], 1.03 per year; 95% confidence interval [CI], 1.02-1.04) and year of diagnosis (OR, 1.64 per 1-year increase; 95% CI, 1.39-1.93); human immunodeficiency virus infection tended to be associated with increased exposure (OR, 1.94; 95% CI, 0.97-3.90). After controlling for age, sex, race, site of disease, human immunodeficiency virus, and year of diagnosis, prior fluoroquinolone exposure was not associated with culture-negative tuberculosis (OR,0.81; 95% CI, 0.41-1.60). Conclusions: Fluoroquinolone use before tuberculosis diagnosis increased significantly during the study period. However, fluoroquinolone exposure was not associated with an increased risk of culture-negative tuberculosis.