Contact screening in tuberculosis: can we identify those with higher risk?

Contact screening in tuberculosis: can we identify those with higher risk?To the Editor: Contact screening, as a strategy to identify recently infected individuals, is part of the tuberculosis (TB) elimination strategy.It follows risk stratification concerning the infectiousness of the index patient, the duration and proximity of exposure, and the susceptibility of the contact [1,2].For its optimisation it is important to know which risk factors are associated with Mycobacterium tuberculosis transmission in order to not over screen or lose at-risk contacts.In view of that, this study aims to identify potential risk factors for M. tuberculosis transmission among contacts of pulmonary TB patients, in a Portuguese TB reference centre.From January to December of 2011, all contacts of confirmed pulmonary TB patients, screened in the TB centre, were questioned about their exposure to the index patient through a questionnaire completed during the medical appointment.Both household and casual contacts were screened, independent of their cumulative exposure.Contacts excluded: those with exposure outdoors (e.g. in the street); those with incomplete characterisation of exposure (e.g.index patients for whom we did not know the symptomatic period); those non-compliant with screening (e.g.contacts who failed tuberculin skin test (TST) reading); and those with a past history of M. tuberculosis infection or TB disease (e.g.contacts verbal report of previous TB disease, contact with a pulmonary TB patient or treatment for latent tuberculosis infection (LTBI)).