Table 2.
Risk Factors for Latent Tuberculosis Infection among Household Contacts of Tuberculosis Cases*
| Variable | No. of Household Contacts | No. with Latent TB Infection (% Prevalence) | Univariable Model† (n = 1,852) |
|
|---|---|---|---|---|
| Relative Risk (95% CI) | P Value | |||
| N | 1,852 | 1,294 (69.9) | ||
| Household contact characteristics | ||||
| Age, yr (continuous) | 1,852 | — | 1.01 (1.01–1.01) | <0.01 |
| Age group, yr | ||||
| 0–4 | 395 | 233 (59.0) | 1 (Reference) | |
| 5–14 | 706 | 475 (67.3) | 1.14 (1.03–1.26) | 0.01 |
| 15–24 | 384 | 294 (76.6) | 1.30 (1.17–1.44) | <0.01 |
| 25–34 | 192 | 146 (76.0) | 1.29 (1.14–1.46) | <0.01 |
| 35–44 | 95 | 77 (81.1) | 1.37 (1.20–1.57) | <0.01 |
| ≥45 | 80 | 69 (86.3) | 1.46 (1.29–1.66) | <0.01 |
| Sex | ||||
| Male | 812 | 564 (69.5) | 1 (Reference) | |
| Female | 1,024 | 729 (71.2) | 1.02 (0.97–1.09) | 0.40 |
| Education level | ||||
| None | 606 | 374 (61.7) | 1 (Reference) | |
| Primary | 851 | 619 (72.7) | 1.18 (1.09–1.27) | <0.01 |
| Secondary or higher | 395 | 301 (76.2) | 1.23 (1.13–1.35) | <0.01 |
| Nutritional status‡ | ||||
| Underweight | 51 | 36 (70.6) | 1.02 (0.85–1.23) | 0.82 |
| Normal | 1,624 | 1,122 (69.1) | 1 (Reference) | |
| Overweight | 163 | 133 (81.6) | 1.18 (1.08–1.29) | <0.01 |
| BCG vaccinated§ | ||||
| No | 479 | 361 (75.4) | 1 (Reference) | |
| Yes | 1,301 | 888 (68.3) | 0.91 (0.85–0.97) | <0.01 |
| Unknown | 65 | 39 (60.0) | 0.80 (0.64–0.98) | 0.04 |
| Cigarette smoking | ||||
| No | 1,352 | 981 (72.6) | 1 (Reference) | |
| Yes | 102 | 80 (78.4) | 1.08 (0.97–1.20) | 0.16 |
| Relation to index case | ||||
| Spouse | 244 | 199 (81.6) | 1 (Reference) | |
| Parent | 67 | 57 (85.1) | 1.04 (0.93–1.17) | 0.47 |
| Child | 771 | 528 (68.5) | 0.84 (0.78–0.91) | <0.01 |
| Sibling | 198 | 142 (71.7) | 0.88 (0.78–0.99) | 0.04 |
| Other|| | 566 | 363 (64.1) | 0.79 (0.71–0.87) | <0.01 |
| Past active tuberculosis | ||||
| No | 1,815 | 1,266 (69.8) | 1 (Reference) | |
| Yes | 23 | 18 (76.3) | 1.12 (0.91–1.39) | 0.29 |
| Alcohol usage | ||||
| No | 1,594 | 1,077 (67.6) | 1 (Reference) | |
| Yes | 249 | 211 (84.7) | 1.25 (1.17–1.34) | <0.01 |
| HIV serostatus | ||||
| Negative | 1,397 | 987 (70.7) | 1 (Reference) | |
| Positive | 179 | 127 (71.0) | 1.00 (0.91–1.11) | 0.93 |
| Closeness to index case | ||||
| Share bed | 312 | 234 (75.0) | 1 (Reference) | |
| Share room but not bed | 783 | 551 (70.4) | 0.94 (0.87–1.01) | 0.10 |
| Different room | 722 | 485 (67.2) | 0.90 (0.82–0.98) | 0.02 |
| Index case characteristics | ||||
| Age group, yr | ||||
| 18–29 | 852 | 614 (72.1) | 1 (Reference) | |
| 30–39 | 601 | 404 (67.2) | 0.93 (0.85–1.03) | 0.16 |
| 40–49 | 287 | 202 (70.4) | 0.98 (0.86–1.11) | 0.71 |
| ≥50 | 112 | 74 (66.1) | 0.92 (0.77–1.09) | 0.33 |
| Sex | ||||
| Male | 968 | 692 (71.5) | 1 (Reference) | |
| Female | 884 | 602 (68.1) | 0.95 (0.88–1.04) | 0.26 |
| Cigarette smoker | ||||
| No | 1,431 | 991 (69.3) | 1 (Reference) | |
| Yes | 403 | 296 (73.5) | 1.06 (0.97–1. 16) | 0.20 |
| Sputum smear status | ||||
| Negative | 429 | 281 (65.5) | 1 (Reference) | |
| Positive | 1,423 | 1,013 (71.2) | 1.09 (0.98–1.21) | 0.12 |
| Chest radiograph findings¶ | ||||
| Normal | 100 | 50 (50.0) | 1 (Reference) | |
| Minimal | 177 | 97 (54.8) | 1.10 (0.82–1.46) | 0.53 |
| Moderately advanced | 641 | 425 (66.3) | 1.33 (1.03–1.72) | 0.03 |
| Far advanced | 989 | 760 (76.9) | 1.54 (1.19–1.98) | <0.01 |
| Lung cavitation¶ | ||||
| Noncavitary disease | 743 | 445 (59.9) | 1 (Reference) | |
| Cavitary disease | 1,060 | 812 (76.6) | 1.28 (1.17–1.40) | <0.01 |
| Duration of cough | ||||
| <30 d | 114 | 70 (61.4) | 1 (Reference) | |
| ≥30 and <60 d | 407 | 256 (62.9) | 1.02 (0.82–1.28) | 0.83 |
| ≥60 and <90 d | 420 | 293 (69.8) | 1.14 (0.91–1.42) | 0.26 |
| ≥90 d | 876 | 656 (74.9) | 1.22 (0.99–1.50) | 0.06 |
| HIV serostatus | ||||
| Negative | 974 | 717 (73.6) | 1 (Reference) | |
| Positive | 878 | 577 (65.7) | 0.89 (0.82–0.97) | 0.01 |
| Household characteristics | ||||
| Housing type | ||||
| Single-family household | 1,005 | 681 (67.8) | 1 (Reference) | |
| Muzigo** | 834 | 601 (72.1) | 1.06 (0.98–1.16) | 0.15 |
| Charcoal or fire smoke exposure | ||||
| Inside household | 398 | 284 (71.4) | 1 (Reference) | |
| Outside household | 1,289 | 886 (68.7) | 0.96 (0.88–1.06) | 0.44 |
| None | 127 | 94 (74.0) | 1.04 (0.87–1.23) | 0.68 |
| Ventilation, No. windows per room | ||||
| >1 | 385 | 251 (65.2) | 1 (Reference) | |
| ≤1 | 1,454 | 1,031 (70.9) | 1.09 (0.97–1.22) | 0.17 |
| Family size, No. in household | ||||
| 1–5 | 821 | 622 (75.8) | 1 (Reference) | |
| 6–10 | 803 | 535 (66.6) | 0.88 (0.81–0.95) | <0.01 |
| >10 | 228 | 137 (60.1) | 0.79 (0.67–0.94) | 0.01 |
Definition of abbreviations: BMI = body mass index; CI = confidence interval; BCG = bacillus Calmette-Guérin; TB = tuberculosis.
Column totals vary across different characteristics because of missing values for some participants. In this analysis, we included only household contacts without coprevalent disease, excluding 81 contacts. Latent tuberculosis infection was defined as an induration reaction greater than or equal to 10 mm in diameter.
The model uses a modified Poisson regression with robust error variance allowing for estimation of relative risks and adjustment for household clustering of contacts.
Nutritional status was assessed for each contact through BMI measurements for adults greater than or equal to 18 years of age and through weight-for-age z scores for child contacts. Individuals were classified as underweight if their z score was less than −2 or a BMI less than 18.5, normal weight if z scores were between −2 and 2 or their BMI was greater than or equal to 18.5 and less than 25, and overweight if z scores were greater than 2 or BMI was greater than or equal to 25.
Evaluated through BCG scar, verified by medical records when available.
Includes other relatives, such as grandparents, grandchildren, aunts, uncles, and cousins. Also includes nonrelatives living in the household.
Radiographic imaging and chest cavitation results were graded by an experienced clinician using the 1961 National Tuberculosis Association classification.
Muzigo households are defined as multifamily household units in the same building.