title: Epidemiology of smear-negative pulmonary tuberculosis in the United States, 1993-2008.
abstract: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  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.
authors: Division of Tuberculosis Elimination, US Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. ns597@columbia.edu
authors: N S
authors: NS
authors: Shah
authors: J S
authors: JS
authors: Cavanaugh
authors: R
authors: R
authors: Pratt
authors: K P
authors: KP
authors: Cain
authors: C
authors: C
authors: Wells
authors: K
authors: K
authors: Laserson
authors: L
authors: L
authors: Nelson
mesh_terms: D000293:Adolescent; D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data; D000368:Aged; D000995:Antitubercular Agents / Q000627:therapeutic use; D001213:Asian / Q000706:statistics & numerical data; D001431:Bacteriological Techniques; D002648:Child; D002675:Child, Preschool; D018563:Disease Notification / Q000706:statistics & numerical data; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data; D005260:Female; D015658:HIV Infections / Q000453:epidemiology; D006630:Hispanic or Latino / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D011237:Predictive Value of Tests; D015995:Prevalence; D011329:Prisoners / Q000706:statistics & numerical data; D018570:Risk Assessment; D012307:Risk Factors; D012959:Socioeconomic Factors; D013183:Sputum / Q000382:microbiology*; D013997:Time Factors; D016896:Treatment Outcome; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology / Q000401:mortality; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D000995:Antitubercular Agents