Volume 19, Number 5—May 2013
CME ACTIVITY - Research
Transmission of Mycobacterium tuberculosis Beijing Strains, Alberta, Canada, 1991–2007
Deanne Langlois-Klassen, Ambikaipakan Senthilselvan, Linda Chui, Dennis Kunimoto, L. Duncan Saunders, Dick Menzies, and Richard Long
Table 3
Risk factors for the recent transmission of Mycobacterium tuberculosis, Alberta, Canada, 1993–2007
| Characteristic | Index case-patient |
Secondary case-patient | Transmission index* | Relative transmission index (95% CI)† |
||
|---|---|---|---|---|---|---|
| Nonclustered | Clustered | Unadjusted | Adjusted | |||
| Sex | ||||||
| F | 330 | 29 | 38 | 0.11 | 1.0 | |
| M |
440 |
44 |
68 |
0.14 |
1.3 (0.9–2.0) |
|
| Age at diagnosis, y | ||||||
| <35 | 185 | 17 | 30 | 0.15 | 1.0 | 1.0 |
| 35–64 | 277 | 35 | 47 | 0.15 | 1.0 (0.6–1.6) | 0.6 (0.4–1.0)‡ |
| >64 |
308 |
21 |
29 |
0.09 |
0.6 (0.4–1.0)§ |
0.4 (0.3–0.7) |
| Population group | ||||||
| Canadian-born | 210 | 46 | 77 | 0.30 | 1.0 | 1.0 |
| Foreign-born, other | 243 | 9 | 9 | 0.04 | 0.1 (0.1–0.2) | 0.1 (0.1–0.2) |
| Foreign-born, Western Pacific |
317 |
18 |
20 |
0.06 |
0.2 (0.1–0.3) |
0.2 (0.1–0.3) |
| Sputum smear status§ | ||||||
| Negative | 364 | 25 | 36 | 0.09 | 1.0 | 1.0 |
| Positive |
357 |
46 |
68 |
0.17 |
1.8 (1.2–2.7) |
1.6 (1.0–2.3)¶ |
| Bacillary load# | ||||||
| Low | 134 | 15 | 25 | 0.17 | 1.0 | |
| High |
56 |
15 |
23 |
0.32 |
1.9 (1.1–3.4) |
|
| Chest radiography | ||||||
| No cavitation | 596 | 44 | 65 | 0.10 | 1.0 | |
| Cavitation |
174 |
29 |
41 |
0.20 |
2.0 (1.3–2.9) |
|
| Drug resistance | ||||||
| Pan-susceptible | 660 | 66 | 98 | 0.13 | 1.0 | |
| Monoresistance | 72 | 4 | 4 | 0.05 | 0.4 (0.1–1.1) | |
| Polyresistance | 28 | 3 | 4 | 0.13 | 1.0 (0.4–2.6) | |
| Multidrug resistance** |
10 |
0 |
0 |
0.00 |
||
| M. tuberculosis strain | ||||||
| Non-Beijing | 597 | 61 | 94 | 0.14 | 1.0 | 0.8 (0.4–1.7) |
| Beijing |
173 |
12 |
12 |
0.06 |
0.5 (0.2–0.8) |
|
| Total | 770 | 73 | 106 | 0.13 | ||
*The number of secondary cases divided by the number of index cases
†Bivariate and multivariate Poisson regression models used an offset of 1 each index case. Variables with p<0.20 in bivariate analysis were eligible for inclusion in the multivariate model. Boldface indicates significance (p<0.05).
‡p = 0.058.
§Sputum smear microscopy was not completed for all cases.
¶p = 0.037.
#Bacillary load was not included in multivariate modeling because of multicollinearity with sputum smear status.
**Multidrug-resistant TB was excluded from bivariate and multivariate analyses.
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