Summary
SETTING
Tijuana, Mexico.
OBJECTIVE
To describe the association between salivary cotinine levels and interferon-γ release assay results.
DESIGN
We conducted a cross-sectional study among persons who inject drugs. Salivary cotinine levels were measured using NicAlert, a semi-quantitative dipstick assay. QuantiFERON TB Gold In-tube (QFT) was used to determine Mycobacterium tuberculosis (Mtb) infection.
RESULTS
Among 234 participants, the prevalence of QFT positivity for NicAlert cotinine categories 0 (nonsmoking), 1 (secondhand smoke exposure or low-level smoking), and 2–6 (regular smoking) were 42.1%, 46.4%, and 65.2%, respectively (Ptrend = 0.012). We found increasing trends in QFT positivity (Ptrend = 0.003) and interferon-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 positivity when included as smoking categories (1 and 2–6 vs. 0), but were independently associated with QFT positivity when included as an ordinal variable (prevalence ratio = 1.09 per +1 cotinine level; 95% confidence interval = 1.02 – 1.16).
CONCLUSION
Our findings suggest that a dose-response relationship exists between tobacco smoke exposure and Mtb infection. Longitudinal studies that use biochemical measures for smoking status are needed to confirm our findings.
introduction: Injection drug use and cigarette smoking are major global health concerns. Limited data exist regarding cigarette smoking behavior and quit attempts among injection drug users (IDUs) in low-and middle-income countries to inform the development of cigarette smoking interventions. We conducted a cross-sectional study to describe cigarette smoking behavior and quit attempts among IDUs in Tijuana, Mexico.
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