Treatment failure in tuberculosis.

Treatment of latent tuberculosis (TB) infection with 3 months of rifampicin/isoniazid is a major part of preventive TB programmes. The effectiveness of treatment of latent TB infection can only be assessed by rates of subsequent breakdown and there are few outcome data for this combination of rifampicin/isoniazid. Therefore, the aim of the present study was to estimate the failure rate following treatment for the latent TB infection. A questionnaire survey was carried out in all parents of children aged <16 yrs who completed treatment for latent TB infection at Leicester Royal Infirmary (Leicester, UK) over the period 1997-2003. Cases of treatment failure were identified by reviewing all re-referrals to the clinic, identifying children developing TB while on treatment and by postal questionnaire to all patients discharged. Of the 400 eligible children, 344 (86%) replied. Three children who had latent TB infection subsequently developed TB disease over the time period. Of those three patients, one developed chest radiograph signs at the end of treatment and two presented with symptoms within 2 yrs of completing treatment. Overall, the mean treatment failure rate was 0.87% (95% confidence interval 0.3-2.5) or 2.2 cases per 1,000 patient-yrs. In conclusion, rates of tuberculosis breakdown after treatment for latent tuberculosis infection with 3 months rifampicin/isoniazid are acceptably low.