Evaluation of tuberculin skin testing in tuberculosis contacts in Victoria, Australia, 2005–2013

Aim: To review the programmatic use of the tuberculin skin test (TST) following tuberculosis (TB) exposure in Victoria, Australia.

Methods: A retrospective review of data collected for public health surveillance was performed to identify contact demographic factors, including bacille Calmette-Guérin (BCG) status and age and outcomes of TST.

Results: Contact tracing was performed for 15 094 people, of whom 13 427 (89.0%) had a TST performed. The TST was positive in 31.4% (95%CI 30.6–32.2) of all contacts, and 48.8% of contacts born outside of Australia. Amongst contacts who were TST-negative at baseline, the conversion rate following exposure was 14.8%. Conversion was most common in those aged 45–54 years, with <12% positivity in both the youngest (<5 years) and oldest (65 years) age groups. Active TB developed in 1.1% of all contacts. Contacts aged <5 years had the highest risk of developing active TB following exposure (3.8%), while low risk was seen in those aged 65 years (0.3%).

Conclusion: Overall, contact tracing and TST in this setting appear to yield a high proportion of people at risk for the development of active TB. The yield of testing in some groups, particularly those aged 65 years, was low, and investigation of alternative strategies should be considered.