Setting: The effect of previously administered bacille Calmette-Guérin (BCG) vaccine on subsequent tuberculin skin tests (TSTs) complicates screening for latent tuberculosis infection (LTBI) in foreign-born persons.
Objective: To determine the usefulness of the TST as a screening test for LTBI in foreign-born persons.
Design: A literature search was performed of published studies that compared tuberculin reactivity amongst BCG-vaccinated and non-vaccinated groups. The percentages of positive reactors in the two groups were then used to calculate a prevalence ratio.
Results: The prevalence ratio varied with the age of the groups tested and the incidence of TB in their countries of origin. The TST performed poorly in vaccinated persons of all ages from countries of low TB incidence, but was a useful screen for LTBI in vaccinated adults from countries of high and intermediate incidence. The test performed poorly as a screening method for vaccinated children under 2 years of age. Its usefulness in vaccinated children aged 2-14 years varied considerably.
Conclusions: The usefulness of the TST as a screening method for LTBI depends on the age of the patient and the incidence of TB in their country of origin.