Table 3.
Characteristics of secondary cases, according to source case smear-status.
| Smear-Negative | Smear-Positive | |
|---|---|---|
| Type-1 (N = 64) | N = 4 (%) | N = 60 (%) |
| Days to diagnosis of contact (mean, SD) | 243 (185) | 119 (143) |
| Close contact | 3 (75) | 52 (87) |
| Household contact | 2 (50) | 35 (58) |
| Average age (SD) | 33 (10) | 33 (19) |
| Median age (IQR) | 31 (12) | 30 (11) |
| <5 years old (all contacts) | 0 | 2 (3) |
| Between 5–14 years old | 0 | 8 (13) |
| HIV (+) | 1 (25) | 3 (5) |
| Foreign-born | 2 (50) | 18 (30) |
| Positive airway secretion smear-status | 1 (25) | 16 (27) |
| Diagnosed within 6 months of arrival to Canada | 0 | 0 |
| Type-2 (N = 33) | N = 4 (%) | N = 29 (%) |
| Days to diagnosis of contact (mean, SD) | 33 (30) | 47 (49) |
| Close contact | 4 (100) | 36 (100) |
| Household contact | 4 (100) | 23 (79) |
| Average age (SD) | 20 (26.4) | 8 (9.5) |
| Median age (IQR) | 7 (22) | 4 (9) |
| <5 years (all contacts) | 2 (50) | 16 (55) |
| Between 5–14 years old | 1 (20) | 9 (31) |
| HIV (+) | 0 | 0 |
| Foreign-born contact | 4 (100) | 9 (31) |
| Diagnosed within 6 months of arrival to Canada | 2 (50) | 6 (21) |
| Type-3 (N = 13) | N = 1 (%) | N = 12 (%) |
| Days to diagnosis of contact (mean, SD) | 279 | 293 (200) |
| Average age (SD) | 55 | 40 (10) |
| Median age (IQR) | 39 (11) | |
| <5 years | 0 | 0 |
| Between 5–14 years old | 0 | 0 |
| HIV (+) | 0 | 0 |
| Foreign-born contact | 0 | 3 (25) |
| Diagnosed within 6 months of arrival to Canada | 0 | 0 |
| Positive airway secretion smear-status | 1 (100) | 6 (50) |
Alberta's prospective, routine contact tracing consists of the gathering of information about the number, type (close or casual), tuberculin skin test (TST), and disease status of contacts for all pulmonary TB cases. We defined close and casual contacts as per the Canadian TB Standards. Assessment of contacts included a symptom enquiry and TST 8–12 weeks after the final contact with the source case (if the contact was not already TST positive), a chest radiograph if symptomatic or TST positive, and sputum for acid-fast bacilli smear and culture if symptomatic or if chest radiograph was abnormal.