Improving tuberculosis contact tracing: the role of evaluations in the home and workplace

In 2004, the tuberculosis (TB) contact screening strategy in Vila Nova de Gaia, Portugal, was changed from targeting only close contacts identified by interviews with the index patient (reflecting national policy) to include visits to the patient?s home and workplace.

To find out 1) whether the new strategy increased adherence to TB screening procedures, 2) whether the strategy identified more at-risk contacts and 3) whether the strategy increased prevention of TB.

We compared TB contact tracing during the periods 2001-2003 and 2004-2006. The numbers of identified and screened contacts and the results of screening procedures (number of patients with active TB and latent TB infection [LTBI] detected per index case) were analysed. The number of instances of active TB prevented and the numbers of contacts that had to be screened to prevent one such instance were calculated and compared for both screening strategies.

Home and workplace visits helped to identify more at-risk contacts (8.4 per index patient) than interview (2.5 per index patient), and improved adherence (87.3% of identified contacts were screened compared to 67.6% previously). More patients with active TB and LTBI were detected (1.4 per index patient compared with 0.75 per index patient previously), and more TB cases were prevented.

The newly implemented contact screening programme, featuring home and workplace evaluation of TB patient contacts, improved adherence to screening procedures, identified more at-risk contacts and should prevent more TB cases in the future.