Table 2. Univariate analysis of factors associated with transmission unconfirmed by DNA fingerprinting in tuberculosis case pairs identified in contact investigations in seven sites, 1996–2000.
| Variable | Transmission unconfirmed (%) (n=156) | Transmission confirmed (%) (n=382) | Odds ratio (95% confidence intervals) | p valuea |
|---|---|---|---|---|
| Relationship between persons in case pairs | ||||
| Shared household | 80 (51) | 180 (47) | 1.2 (0.8 to 1.7) | NS |
| Friends/social | 55 (35) | 156 (41) | 0.8 (0.5 to 1.2) | NS |
| Shared workplace | 11 (7) | 12 (3) | 2.3 (1.1 to 5.4) | 0.04 |
| Other | 10 (6) | 34 (9) | 1.0 (0.6 to 1.5) | NS |
| Characteristics of source cases | ||||
| Sputum smear-negative | 56 (36) | 73 (19) | 2.4 (1.6 to 3.6) | <0.0001 |
| Cavitary disease | 64 (41) | 197 (52) | 0.7 (0.5 to 1.0) | NS |
| Characteristics of secondary cases | ||||
| Foreign-born | 73 (47) | 60 (16) | 4.7 (3.1 to 7.2) | <0.0001 |
| Previous tuberculosis | 5 (3.0) | 12 (3.0) | 1.1 (0.4 to 3.7) | NS |
| <15 yrs | 8 (5) | 65 (17) | 0.4 (0.2 to 0.8) | 0.007 |
| >65 yrs | 16 (11) | 21 (6) | 1.8 (0.9 to 3.6) | NS |
| HIV positive | 13 (8) | 33 (9) | 1.0 (0.5 to 1.9) | NS |
| Characteristics of case pairs | ||||
| Both white | 14 (9) | 42 (11) | 0.5 (0.4 to 1.5) | NS |
| Both black | 62 (40) | 221 (58) | 0.5 (0.3 to 0.7) | 0.005 |
| Both Hispanic | 21 (14) | 46 (12) | 1.1 (0.7 to 2.0) | NS |
| Both Asian or Pacific Islander | 35 (22) | 29 (8) | 3.5 (2.1 to 6.0) | <0.0001 |
| Racial discrepancy | 24 (15) | 40 (11) | 1.2 (0.9 to 1.4) | NS |
| Age difference >10 yrs | 88 (56) | 198 (52) | 1.2 (0.8 to 1.7) | NS |
aNS, not significant.