Table 2.
Risk factors for QuantiFERON®-TB Gold-positivity, all participants with non-indeterminate result (n=9,810)
| Risk factors | Proportion QFT-positive (%) | Univariable analysis | Adjusted for age and sex only | Adjusted for age, sex and other covariates(1) | ||||
|---|---|---|---|---|---|---|---|---|
| Risk ratio (95% CI) | P | Adjusted risk ratio (95% CI) | P | Adjusted risk ratio (95% CI) | P | |||
| Sex | Female | 494/4867 (10.2%) | 1.00 (ref) | - | 1.00 (ref) | - | 1.00 (ref) | |
| Male | 452/4943 (9.1%) | 0.90 (0.80, 1.02) | 0.09 | 0.89 (0.79, 1.01) | 0.07 | 0.92 (0.82, 1.04) | 0.18 | |
| Age, years | - | 1.17 (1.13, 1.22) | <0.001 | 1.17 (1.13, 1.22) | <0.001 | 1.14 (1.10, 1.19) | <0.001 | |
| Parental education(2) | University / polytechnic | 128/1881 (6.8%) | 1.00 (ref) | - | 1.00 (ref) | - | 1.00 (ref) | |
| Secondary school or lower | 818/7929 (10.3%) | 1.52 (1.27, 1.81) | <0.001 | 1.43 (1.20, 1.71) | <0.001 | 1.16 (0.95, 1.42) | 0.14 | |
| Type of residence | Centrally heated | 170/2365 (7.2%) | 1.00 (ref) | - | 1.00 (ref) | - | 1.00 (ref) | |
| Not centrally heated | 377/3772 (10.0%) | 1.39 (1.17, 1.65) | <0.001 | 1.36 (1.14, 1.62) | <0.001 | 1.10 (0.92, 1.33) | 0.29 | |
| Ger (Yurt) | 399/3673 (10.9%) | 1.51 (1.27, 1.79) | <0.001 | 1.45 (1.22, 1.72) | <0.001 | 1.09 (0.88, 1.35) | 0.41 | |
| Monthly household income(3), 100 US dollars (4) | - | 0.97 (0.95, 0.99) | <0.001 | 0.97 (0.96, 0.99) | 0.003 | 0.99 (0.98, 1.01) | 0.49 | |
| Home ownership | No | 223/2113 (10.6%) | 1.00 (ref) | - | 1.00 (ref) | - | 1.00 (ref) | |
| Yes | 723/7697 (9.4%) | 0.89 (0.77, 1.03) | 0.11 | 0.90 (0.78, 1.03) | 0.13 | 0.95 (0.83, 1.09) | 0.48 | |
| Number of people/room(3) | - | 1.06 (1.03, 1.10) | <0.001 | 1.05 (1.02, 1.09) | 0.003 | 1.01 (0.97, 1.05) | 0.63 | |
| Month of sampling | Jun-Nov | 247/3259 (7.6%) | 1.00 (ref) | - | 1.00 (ref) | - | 1.00 (ref) | |
| Dec-Feb | 381/3671 (10.4%) | 1.37 (1.18, 1.60) | <0.001 | 1.31 (1.12, 1.53) | <0.001 | 1.19 (1.00, 1.41) | 0.06 | |
| Mar-May | 318/2880 (11.0%) | 1.46 (1.24, 1.71) | <0.001 | 1.45 (1.23, 1.69) | <0.001 | 1.31 (1.10, 1.56) | 0.003 | |
| No. of people in household smoking indoors | 0 | 534/6249 (8.5%) | 1.00 (ref) | <0.001(5) | 1.00 (ref) | <0.001(5) | 1.00 (ref) | 0.006(5) |
| 1 | 347/3140 (11.1%) | 1.29 (1.14, 1.47) | <0.001 | 1.26 (1.11, 1.44) | <0.001 | 1.19 (1.04, 1.35) | 0.009 | |
| 2 or more | 65/421 (15.4%) | 1.81 (1.42, 2.29) | <0.001 | 1.68 (1.33, 2.13) | <0.001 | 1.30 (1.02, 1.64) | 0.03 | |
| Child actively smoking(3) | No | 944/9761 (9.7%) | 1.00 (ref) | - | 1.00 (ref) | - | 1.00 (ref) | - |
| Yes | 2/49 (4.1%) | 0.42 (0.11, 1.64) | 0.21 | 0.40 (0.10, 1.54) | 0.18 | 0.40 (0.10, 1.57) | 0.19 | |
| BCG scar | Absent | 195/1958 (10.0%) | 1.00 (ref) | - | 1.00 (ref) | - | ||
| Present | 751/7852 (9.6%) | 0.96 (0.83, 1.12) | 0.60 | 0.98 (0.84, 1.14) | 0.78 | |||
| Body mass index(3), kg/m2 | - | 1.02 (0.99, 1.04) | 0.17 | 1.00 (0.97, 1.02) | 0.84 | - | ||
| Body fat(3), % | - | 0.99 (0.98, 1.00) | 0.24 | 1.00 (0.99, 1.01) | 0.56 | 1.00 (ref) | - | |
| Household PTB contact | No | 788/9437 (8.4%) | 1.00 (ref) | - | 1.00 (ref) | - | 4.75 (4.13, 5.46) | <0.001 |
| Yes | 158/373 (42.4%) | 5.07 (4.43, 5.81) | <0.001 | 4.96 (4.33, 5.68) | <0.001 | |||
| Time spent outdoors, hours / day(3) |
<1 | 414/4120 (10.1%) | 1.00 (ref) | 0.17(4) | 1.00 (ref) | 0.13(4) | 1.00 (ref) | 0.56(4) |
| 1-2 | 290/3013 (9.6%) | 0.96 (0.83, 1.10) | 0.55 | 0.95 (0.83, 1.10) | 0.49 | 0.96 (0.83, 1.10) | 0.53 | |
| >2 | 242/2677 (9.0%) | 0.90 (0.77, 1.05) | 0.17 | 0.89 (0.76, 1.03) | 0.13 | 0.95 (0.80, 1.12) | 0.52 | |
| Deseasonalized serum 25(OH) D(3), ng/ml | ≥10 | 656/7325 (9.0%) | 1.00 (ref) | - | 1.00 (ref) | - | ||
| <10 | 285/2431 (11.7%) | 1.32 (1.16, 1.50) | <0.001 | 1.20 (1.05, 1.37) | 0.01 | 1.23 (1.08, 1.40) | 0.002 | |
Abbreviations: 25(OH)D, 25-hydroxyvitamin D; BCG, Bacille Calmette–Guérin vaccine; CI, confidence interval; PTB, pulmonary tuberculosis; QFT, QuantiFERON®-TB Gold; US, United States.
(1) Adjusted for age, sex and the following covariates with P<0.2 in age/sex adjusted analysis: parental education, type of residence, monthly household income, home ownership, number of people per room, month of sampling, exposure to household environmental tobacco smoke, child active smoking status, household PTB contact and serum 25(OH)D concentration; 9,745 participants with non-missing data for all covariates included in this multivariable analysis.
(2) Highest educational level attained by either parent
(3) Missing values (income, 10 missing; number per room, 1 missing; body mass index, 2 missing; body fat, 42 missing; 25(OH)D, 54 missing)
(4) 1$=1000MNT
(5) P-value for trend