Table 3. Erythema-based referral criteria for chemoprophylaxis by exposure group and tuberculosis incidence in each stratum of the criteria.*.
| Exposure group† | Erythema in the contact investigation (mm) |
Increase in erythema (mm)‡ |
Chemoprophylaxis referral criteria |
Number of subjects observed§ |
Tuberculosis incidence | |
| Number | % | |||||
| 1 | 30+ | Any | Referred | 20 | 2 | 10.0 |
| <30 | Any | Not referred | 2 | 0 | 0 | |
| 2 | 30+ | 20+ | Referred | 40 | 0 | 0 |
| 30+ | <20 | Not referred | 2¶ | 0 | 0 | |
| <30 | Any | Not referred | 27 | 3 | 11.1 | |
| 3 | 30+ | 20+ | Referred | 47 | 2 | 4.3 |
| 30+ | <20 | Not referred | 3 | 0 | 0 | |
| <30 | Any | Not referred | 49 | 3 | 6.1 | |
| 4 | 60+ | Any | Referred | 21 | 1 | 4.8 |
| 50-59 | 30+ | Referred | 14 | 0 | 0 | |
| 50-59 | <30 | Not referred | 6 | 0 | 0 | |
| <50 | Any | Not referred | 315 | 2 | 0.6 | |
* : Subjects with tuberculosis diagnosed before or in the tuberculin skin test were not used in the analysis.
† : Group 1, homeroom classmates; Group 2, students who shared special classes or extracurricular activities with the case; Group 3, third-grade students after excluding those who belonged to exposure group 1 and group 2; Group 4, first- or second-grade students after excluding those who belonged to exposure group 2.
‡ : Increase in the erythema size from the regular school-entry checkup to the contact investigation.
§ : One subject in the exposure group 1, 5 subjects in the exposure group 3, and 3 subjects in the exposure group 4, all of whom did not receive chemoprophylaxis, were excluded because of missing values for erythema measurement at school entry.
¶ : One subject received chemoprophylaxis prescribed by a physician at a medical facility.