Contact tracing for tuberculosis and treatment for latent infection in a low incidence country

OBJECTIVE: To determine the yield of contact tracing after exposure to active tuberculosis (TB) cases in a low incidence area for TB as well as completion rate and tolerance to treatment for latent TB infection (LTBI). METHODS: Retrospective study based on a database including all patients evaluated in Geneva during contact tracing procedures; review of medical records of contacts for whom treatment of LTBI was indicated. RESULTS: 3582 subjects were screened over 10 years (on average 4.3 contacts per index case); 8 (0.2%) had active TB. LTBI was detected in 28% of subjects screened. Foreign origin, exposure and contagiousness of index case were predictive of LTBI. Of the 996 subjects with LTBI, files of 705 subjects followed at our centre were reviewed: treatment was indicated in 571 (81%). Side-effects led to interruption of treatment for LTBI in 32 cases (6.9% of subjects treated); 227 subjects eligible for treatment (40%) either refused or stopped treatment, or were lost to follow-up. Completion rate was 67%. CONCLUSIONS: In a low-incidence environment for TB, contact tracing procedures had a very low yield for detection of active TB cases; acceptance and completion rates for LTBI therapy were in agreement with recent studies..