Tuberculosis: which patients do not identify their contacts?

It is not known what the magnitude of non-identified TB contacts is in our country, or the reasons why contacts at risk are not identified.

The purpose of this study was to analyze the determinants associated with non-identification of contacts.

This cross-sectional study included all cases of pulmonary tuberculosis diagnosed and treated in the Chest Disease Centre of Vila Nova de Gaia and their contacts, from 1st January to 31st December 2010. It included information collected from patients related to the identification of contacts in risk, and the information collected by the Public Health Unit during home, work and social places visits.

During the period of study, 61 cases of pulmonary TB were diagnosed: 41 cases (67.2%) identified all their contacts and 20 cases (32.8%) did not. 646 contacts were identified: 154 (23.8%) were identified only by the Public Health Unit (mean age of 40.67), and 492 (76.2%) were identified by the index cases (mean age of 33.25), (p=0.001). A mean of 10.59 contacts were identified per index case, of which, 83 (19.3%) screened positive. From those identified by the Public Health Unit, 10 (9.8%) had LTBI and 5 (4.9%) had active TB, and by the index case 61 (18.6%) had LTBI and 7 (2.1%) had active TB (crude OR=1.52; CI=0.83-2.79). The multivariate analysis showed that employment (adjusted OR=4.82; 95%CI=1.71-13.54) was associated to non-identification of contacts and patients preferably tended to identify relatives and co-habitants (adjusted OR=0.22; 95%CI=0.10-0.47).

TB patients tend to identify relatives and co-habitant contacts; contact at place of employment was found to be an independent risk factor for not being identified.