[Efficacy of the treatment for latent tuberculosis infection and delayed reactivation of tuberculosis].

PURPOSE: To evaluate the efficacy of treatment for latent tuberculosis infection and delayed reactivation of tuberculosis. METHOD: During a large tuberculosis outbreak, 129 individuals who were in close contact with tuberculosis patients and subsequently tested strongly positive by the tuberculin skin test were followed up for 10 years after identification of the source case. RESULT: Of the 129 individuals, 105 received treatment for latent tuberculosis infection for 6 months as per recommendation, while the remaining 24 did not receive treatment, because most of them were above 30 years of age and were therefore discouraged from receiving treatment, as was done in the earlier times in Japan. Of the 105 individuals, 5 (4.8%) were newly diagnosed with tuberculosis, and the average duration from identification of the source case to reactivation of tuberculosis was 53 months. Of the 24 individuals who did not receive treatment for latent tuberculosis infection, 6 (25.0%) were newly diagnosed with tuberculosis, and the average duration from identification of the source case to reactivation of tuberculosis was 8.2 months. CONCLUSION: The risk of active tuberculosis was reduced by 81.0% with treatment for latent tuberculosis infection, compared with that without treatment. Delayed reactivation of tuberculosis was observed among patients treated with isoniazid for latent tuberculosis infection for 6 months.