Tuberculosis incidence among contacts of active pulmonary tuberculosis.

BACKGROUND

Treatment of latent tuberculosis (TB) infection (LTBI) in Brazil is recommended only in the case of contacts of pulmonary smear-positive TB patients aged<or=15 years with a tuberculin skin test (TST)>or=10 mm and no previous bacille Calmette-Guérin (BCG) vaccination or with a TST>or=15 mm regardless of previous BCG vaccination.

OBJECTIVE

To evaluate the 2-year incidence and predictors of TB among contacts who did not meet the Brazilian criteria for LTBI treatment.

DESIGN

Retrospective cohort study. Contacts aged between 12 and 15 years and those aged>or=15 years who did not meet the Brazilian criteria for LTBI treatment were enrolled in the study.

RESULTS

TB incidence was 3.2% (22/667), with an estimated TB rate of 1649 per 100000 population. Risk of TB was greater among the 349 contacts with TST>or=5 mm (5.4%) compared to the 318 contacts with TST<5 mm (0.9%; RR 6.04, 95%CI 1.7-20.6).

CONCLUSION

The high incidence of TB among contacts who did not meet the Brazilian criteria for LTBI treatment strongly suggests that these criteria should be reviewed. Furthermore, even among BCG-vaccinated contacts, TST induration>or=5 mm was the only variable that predicted the development of TB disease within 2years.