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Free Content Epidemiology of smear-negative pulmonary tuberculosis in the United States, 1993–2008

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BACKGROUND: Smear-negative tuberculosis (TB) is difficult to diagnose and has been associated with poor treatment outcomes and excessive mortality, particularly in high human immunodeficiency virus (HIV) prevalent settings. However, few studies have used mycobacterial culture to rigorously confirm all smear-negative TB cases in a population-based cohort.

DESIGN: We included all culture-confirmed, pulmonary TB cases reported to the US National TB Surveillance System from 1993 to 2008. We analyzed smear-negative TB risk factors and survival, as compared to smear-positive TB. We calculated prevalence ratios (PRs) and adjusted for confounders (aPR).

RESULTS: From 1993 to 2008, 159 121 cases of culture-confirmed pulmonary TB were reported in the United States, of which 58 786 (37%) were sputum smear-negative. Smear-negative TB cases were more likely to be foreign-born (aPR 1.10, 95%CI 1.08–1.12), incarcerated (aPR 1.52, 95%CI 1.48–1.56) or HIV-infected (aPR 1.27, 95%CI 1.24–1.30). Hispanics and non-Hispanic Blacks were less likely to have smear-negative TB (respectively aPR 0.87, 95%CI 0.85–0.89 and aPR 0.90, 95%CI 0.89–0.92). Smear-negative TB cases had lower mortality (aRR 0.78, 95%CI 0.74–0.81), independent of HIV status.

CONCLUSION: Smear-negative TB represents a large proportion of TB cases in the United States, and occurs more often among persons in groups more likely to undergo TB screening. The lower mortality may indicate earlier TB detection, and underscores the need for continued vigilance in screening of high-risk persons.

Keywords: diagnosis; smear microscopy; tuberculosis

Document Type: Research Article


Affiliations: 1: Division of Tuberculosis Elimination, US Centers for Disease Control and Prevention, Atlanta, Georgia, USA; Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, USA 2: Division of Tuberculosis Elimination, US Centers for Disease Control and Prevention, Atlanta, Georgia, USA 3: Division of Tuberculosis Elimination, US Centers for Disease Control and Prevention, Atlanta, Georgia, USA; Northrop Grumman, Falls Church, Virginia, USA

Publication date: 2012-09-01

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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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