[Relapse rate of tuberculosis treated with standard regimen of chemotherapy]

Japanese standard of Tuberculosis treatment indicates that six months treatment with isoniazid, rifampicin and pyrazinamide can be extended to nine months under certain conditions such as diabetics. We have little information on the validity of the duration of treatment as yet.

The treatment result of isoniazid and rifampicin susceptible new TB cases treated with the regimen including isoniazid, rifampicin and pyrazinamide were analyzed with the categorization of duration of treatment. Risk factors of bacteriological relapse were evaluated.

Among 839 cases treated at the facilities of Ryoken members in 2005, 27 cases relapsed bacteriologically. The rate of relapse (3%) was the same between those that were treated for six months and those treated for nine months. Diabetic cases, immuno-compromised cases and extensive cavitary cases showed higher risk of relapse if they were treated with six months regimen than in cases treated with nine months regimen. Those that were culture positive even after 2 months of treatment showed high rate (6-7%) of relapse if they were treated with six to nine months regimen but no relapse was observed if they were treated for >40 weeks or if they were treated for more than 6 months after conversion to negative culture.

Our results did not indicate that Japanese standard of TB treatment should be changed regarding extension of treatment for diabetics and serious cases. Those who remained culture positive after 2 months of treatment should be treated >9 months and/or at least 6 months after culture negative conversion.