Yield of tuberculosis contact investigation in a low-incidence country.

Background: Tuberculosis (TB) contact tracing is a valid public health measure to control the spread of TB infection in low-burden settings. The aim of this study was to assess the yield of the Piedmont TB contact investigation program and to evaluate the role of its main determinants.

Methods: The Piedmont TB notification systems were used to identify index TB cases. All cases were classified by contagiousness (sputum-smear-positive, AFB+; culture-positive, CULT+; other-than-defined). TB contacts were screened for active and latent TB infection by clinical manifestations and Tuberculin Skin Test (TST).

Results: 833 index TB cases with at least one contact were identified; 4441 contacts were screened, and 3942 (82.8%) were evaluated. TB contacts aged ≤ 35 years, regular and household contacts had a higher probability of being evaluated; foreign-born TB contacts were the least traceable. Higher rates of TB infection were observed in contacts at 35 years of age or younger who also lived in the same household with index cases or exposed to AFB+ or CULT+ index cases.

Conclusion: More efforts should be focused on young TB contacts, since they are likely to be new infections. An early identification and treatment of TB Infection in this group contributes to the prevention and control of TB transmission. The program should also be extended to the contacts of CULT+ cases.