Cigarette-Smoking Intensity and Interferon-Gamma Release Assay Conversion among Persons Who Inject Drugs: A Cohort Study
Table 1
Demographic and behavioral characteristics of participants with negative QFT results (IFN-γ < 0.35 IU/mL) at baseline, included versus not included in the analysis; Tijuana, Mexico, 2006–2008.
Characteristic
Included
Not included
value*
(%)
(%)
Gender
0.806
Male
107 (82.9)
178 (84.0)
Female
22 (17.1)
34 (16.0)
Age, median (IQR)
38 (32–43)
37 (30–42)
0.247
Education
0.389
Up to primary
39 (30.2)
76 (35.8)
Primary to middle
60 (46.5)
83 (39.2)
High school and higher
30 (23.3)
53 (25.0)
Unstable housing
0.357
No
113 (87.6)
178 (84.0)
Yes
16 (12.4)
34 (16.0)
History of incarceration
0.719
No
78 (60.5)
124 (58.5)
Yes
51 (39.5)
88 (41.5)
HIV infection
0.366
No
123 (95.3)
197 (92.9)
Yes
6 (4.7)
15 (7.1)
Alcohol
0.154
None
76 (58.9)
134 (63.2)
Less than twice per week
31 (24.0)
57 (26.9)
Twice per week or more
22 (17.1)
21 (9.9)
Smoked cigarette during study periods (18 months)
0.919
No
4 (3.1)
7 (3.3)
Yes
125 (96.9)
205 (96.7)
Number of cigarettes smoked daily, median (IQR)
10.5 (6–15)
12.5 (7–19)
0.023
Number of cigarettes smoked daily (quartiles)
0.058
0–5
30 (23.3)
41 (19.3)
6–10
36 (27.9)
50 (23.6)
11–15
37 (28.7)
49 (23.1)
16+
26 (20.2)
72 (34.0)
QFT conversion at 18 mos (IFN-γ ≥ 0.70 IU/mL)
No
77 (59.7)
—
Yes
52 (40.3)
—
values for the difference between included versus excluded participants were generated using the Pearson’s test for categorical variables and the Wilcoxon rank sum for continuous variables. IFN-γ: interferon-gamma; QFT: QuantiFERON-TB Gold In-Tube; IQR: interquartile range.
