title: Risk of progression to active tuberculosis among foreign-born persons with latent tuberculosis.
abstract: BACKGROUND
  Increased risk for tuberculosis (TB) disease has been identified in foreign-born persons in the United States, particularly during the first 5 years after their arrival in the United States. This could be explained by undetected TB disease at entry, increased prevalence of latent TB infection (LTBI), increased progression from LTBI to TB, or a combination of these factors.
  
  
  METHODS
  We performed a cluster analysis of TB cases in Boston and a case-control study of risk factors for TB with an unclustered isolate among Boston residents with LTBI to determine whether such persons have an increased risk for reactivation of disease.
  
  
  RESULTS
  Of 321 case patients with TB seen between 1996 and 2000, 133 isolates were clustered and 188 were not. In multivariate analysis, foreign birth was associated with an unclustered isolate (odds ratio [OR], 2.2; 95% confidence interval [CI], 1.2 to 3.8; p < 0.01), while being a close contact of a TB case was negatively associated (OR, 0.22; 95% CI, 0.07 to 0.73; p = 0.02). When 188 TB patients with unclustered isolates were compared to 188 age-matched control subjects with LTBI, there was no association between the occurrence of TB and foreign birth (OR, 0.71; 95% CI, 0.42 to 1.3); among foreign-born persons, there was no association between the occurrence of TB and being in the United States <or= 5 years (OR, 0.90; 95% CI, 0.56 to 1.44).
  
  
  CONCLUSIONS
  We conclude that the increased risk for TB among foreign-born persons in the United States may be attributable to the increased prevalence of LTBI among foreign-born persons or the increased prevalence of active disease at arrival in the United States, but not to an increased rate of reactivation among persons with LTBI.
authors.affiliation: Department of Medicine, Section of Infectious Diseases, School of Medicine, Boston University, Boston, USA.
authors.forename: Shalini
authors.initials: S
authors.lastname: Patel
authors.forename: Armen E
authors.initials: AE
authors.lastname: Parsyan
authors.forename: Julia
authors.initials: J
authors.lastname: Gunn
authors.forename: M Anita
authors.initials: MA
authors.lastname: Barry
authors.forename: Carrie
authors.initials: C
authors.lastname: Reed
authors.forename: Sharon
authors.initials: S
authors.lastname: Sharnprapai
authors.forename: C Robert
authors.initials: CR
authors.lastname: Horsburgh
mesh_terms: D001900:Boston; D002353:Carrier State; D016022:Case-Control Studies; D016000:Cluster Analysis; D018450:Disease Progression; D004641:Emigration and Immigration; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D015995:Prevalence; D012307:Risk Factors; D014376:Tuberculosis / Q000453:epidemiology* / Q000473:pathology*