Cigarette-Smoking Intensity and Interferon-Gamma Release Assay Conversion among Persons Who Inject Drugs: A Cohort Study

Table 3

Adjusted risk ratios for QFT conversion (IFN-γ ≥ 0.70 IU/mL) at 18 months based on multivariable Poisson regression models with robust variance; Tijuana, Mexico, 2006–2008.

Variable	Risk Ratio (95% Confidence Interval)
	Bivariate Model	Reduced Model	Final Model
Number of cigarettes smoked daily (quartiles)
0–5	1.00	1.00	1.00
6–10	0.75 (0.37–1.55)	1.04 (0.53–2.04)	0.86 (0.46–1.63)
11–15	0.53 (0.23–1.20)	0.73 (0.36–1.51)	0.54 (0.25–1.17)
≥16	0.59 (0.24–1.43)	0.79 (0.34–1.83)	0.74 (0.33–1.64)
Education
High school or higher		1.00	1.00
Less than high school		2.83 (1.08–7.42)	2.60 (0.96–7.03)
Age
+10 years			1.25 (0.80–1.94)
Gender
Male			1.00
Female			0.81 (0.34–1.93)
Alcohol use
<2x per week			1.00
≥2x per week			1.04 (0.52–2.08)

IFN-γ: interferon-gamma; QFT: QuantiFERON-TB Gold In-Tube.