Objectives: To elucidate difference in transmissibility between bronchial and laryngeal TB.
Subjects and methods: The subjects of this retrospective study were 147 patients with bronchial TB and 28 patients with laryngeal TB registered in Aichi Prefecture between 1985 and 2003. All recorded files were reviewed to identify multiple TB patients in the same transmission group. When multiple patients with a registration interval of less than 10 years were found in the same transmission group, the first patient was considered as the index case, and the other patients were regarded as secondary cases.
Results: Bronchial TB patients were found in 0.17 per 100,000 population, and laryngeal TB patients in 0.032 per 100,000. Bronchial TB patients occupied 0.55% of total TB patients, and laryngeal TB patients occupied 0.10%. Significant differences were found in patients' proportion between bronchial and laryngeal TB; as to patients with non-cavitary infiltration (73.5% vs 50.0%, p<0.05), female patients (75.4% vs 39.3%, p<0.001), patients aged twenties (13.6% vs 0%, p<0.05), cavitary lesions (7.5% vs 21.4%, p<0.05), male patients (24.5% vs 60.7%, p<0.001), and patients aged thirties (6.1% vs 17.9%, p<0.05). However, no significant difference was observed in the patients' proportion between bronchial and laryngeal TB patients as to positive smear (64.7% vs 53.6%). Three patients with bronchial TB and other three patients with laryngeal TB were found to be the index patients. The proportion of the index patients among overall bronchial and laryngeal TB patients was 2.0% and 10.7% (p<0.05), while they were 2.1% and 20.0% (p< 0.05), respectively, in smear-positive patients, and 0% and 20.0% (p=0.18, not significant) in those patients with no chest pathology.
Conclusion: These findings suggest that bronchial TB is less infectious than laryngeal TB.