title: Dose-response association between salivary cotinine levels and Mycobacterium tuberculosis infection.
abstract: METHODS
  Tijuana, Mexico.
  
  
  OBJECTIVE
  To describe the association between salivary cotinine levels and interferon-gamma (IFN-γ) release assay results.
  
  
  METHODS
  We conducted a cross-sectional study among injection drug users. Salivary cotinine levels were measured using NicAlert, a semi-quantitative dipstick assay. QuantiFERON©-TB Gold In-Tube (QFT-GIT) was used to determine Mycobacterium tuberculosis infection.
  
  
  RESULTS
  Among 234 participants, the prevalence of QFT-GIT positivity for NicAlert cotinine categories 0 (non-smoking), 1 (second-hand smoke exposure or low-level smoking) and 26 (regular smoking) were respectively 42.1%, 46.4% and 65.2% (Ptrend 0.012). We found increasing trends in QFT-GIT positivity (Ptrend 0.003) and IFN-γ concentrations (Spearman's r 0.200, P 0.002) across cotinine levels 0 to 6. In multivariable log-binomial regression models adjusted for education, cotinine levels were not associated with QFT-GIT positivity when included as smoking categories (1 and 26 vs. 0), but were independently associated with QFT-GIT positivity when included as an ordinal variable (prevalence ratio 1.09 per 1 cotinine level, 95%CI 1.021.16).
  
  
  CONCLUSIONS
  Our findings suggest that a dose-response relationship exists between tobacco smoke exposure and M. tuberculosis infection. Longitudinal studies that use biochemical measures for smoking status are needed to confirm our findings.
authors.affiliation: Joint Doctoral Program in Public Health (Global Health), San Diego State University/University of California San Diego, San Diego, California, USA.
authors.forename: S S
authors.initials: SS
authors.lastname: Shin
authors.forename: R
authors.initials: R
authors.lastname: Laniado-Laborin
authors.forename: P G
authors.initials: PG
authors.lastname: Moreno
authors.forename: T E
authors.initials: TE
authors.lastname: Novotny
authors.forename: S A
authors.initials: SA
authors.lastname: Strathdee
authors.forename: R S
authors.initials: RS
authors.lastname: Garfein
mesh_terms: D000328:Adult; D016009:Chi-Square Distribution; D003367:Cotinine / Q000378:metabolism*; D003430:Cross-Sectional Studies; D004305:Dose-Response Relationship, Drug; D055030:Drug Users; D005260:Female; D006801:Humans; D059425:Interferon-gamma Release Tests; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D015999:Multivariate Analysis; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D011237:Predictive Value of Tests; D015995:Prevalence; D011934:Reagent Strips; D012307:Risk Factors; D012463:Saliva / Q000378:metabolism*; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology / Q000378:metabolism*; D015819:Substance Abuse, Intravenous / Q000453:epidemiology; D014376:Tuberculosis / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology*
chemical_list: D011934:Reagent Strips; D003367:Cotinine