title: Smoking in tuberculosis patients increases the risk of infection in their contacts.
abstract: OBJECTIVE
  To determine the risk of latent tuberculous infection (LTBI) among contacts of smokers with tuberculosis (TB).
  
  
  METHODS
  A study was conducted to determine the prevalence of LTBI among contacts of TB cases aged >14 years in Catalonia, Spain. A survey was carried out for each TB case and their contacts. LTBI was diagnosed using the tuberculin skin test (≥5 mm). The risk of LTBI associated with smoking was determined by multi-variate logistic regression analysis, with adjusted odds ratio (aOR) and their 95% confidence intervals (CI).
  
  
  RESULTS
  The smoking prevalence among TB cases was 40.7% (439/1079). The prevalence of LTBI among their contacts was 29.7% (2281/7673). It was higher among contacts of smoking index cases (35.3%) than among those of non-smokers (25.7%). Smoking was independently associated with an increased risk of LTBI among contacts (aOR 1.5, 95%CI 1.3-1.7), and was estimated to be responsible for 12.8% of infections.
  
  
  CONCLUSIONS
  Index case smoking increases the risk of LTBI and should be systematically investigated. A reduction in smoking could lower the risk of infection substantially.
authors.affiliation: Department of Health, Generalitat de Catalunya (Autonomous Government of Catalonia), Barcelona, Spain. pere.godoy@gencat.cat
authors.forename: P
authors.initials: P
authors.lastname: Godoy
authors.forename: J A
authors.initials: JA
authors.lastname: Caylà
authors.forename: G
authors.initials: G
authors.lastname: Carmona
authors.forename: N
authors.initials: N
authors.lastname: Camps
authors.forename: J
authors.initials: J
authors.lastname: Álvarez
authors.forename: M
authors.initials: M
authors.lastname: Alsedà
authors.forename: S
authors.initials: S
authors.lastname: Minguell
authors.forename: A
authors.initials: A
authors.lastname: Rodés
authors.forename: N
authors.initials: N
authors.lastname: Altet
authors.forename: J-M
authors.initials: JM
authors.lastname: Pina
authors.forename: I
authors.initials: I
authors.lastname: Barrabeig
authors.forename: Á
authors.initials: Á
authors.lastname: Orcau
authors.forename: I
authors.initials: I
authors.lastname: Parron
authors.forename: J
authors.initials: J
authors.lastname: March
authors.forename: N
authors.initials: N
authors.lastname: Follia
authors.forename: M
authors.initials: M
authors.lastname: Sabater
authors.forename: Á
authors.initials: Á
authors.lastname: Domínguez
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016358:Contact Tracing; D005260:Female; D006801:Humans; D055985:Latent Tuberculosis / Q000175:diagnosis / Q000453:epidemiology*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012306:Risk; D012907:Smoking / Q000453:epidemiology*; D013030:Spain / Q000453:epidemiology; D014374:Tuberculin Test; D014376:Tuberculosis / Q000453:epidemiology / Q000635:transmission*; D055815:Young Adult