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The health surveillance is a helpful tool for controlling and limiting the transmission of tuberculosis (TB) in healthcare workers. Early detection and treatment of Latent TB Infection (LTBI) are essential in the prevention of the spread of TB. As known, the most diffuse screening test for TB, the Tuberculin Skin Test (TST) has many limitations, including being confounded by previous BCG vaccination or exposure to non-tuberculous mycobacteria. In recent years, new “in vitro” assays, such as QuantiFERON TB-Gold (QFT-G), seem to have higher specificity than TST, but their elevated costs limit adoption in clinical practise.
Methods
An analysis was conducted among healthcare students, before their first clinical training in a hospital. According to NICE guidelines (2006), a “two-step strategy” (TST followed by a QFT-G, only if TST was positive) was used. Only if both TST and QTF-G were positive, subjects had a chest X-ray and were sent to a lung specialist for the diagnosis of LTBI and the prescription of a specific drug treatment.
Results
We analyzed 1,299 healthcare students (women were 65.43%; mean age: 24.26 ± 4.42 years). Only 33 subjects (2.54% of the population) were TST positive, of whom 18 came from a foreign country (Eastern Europe, Africa). QFT-G was positive only in 8 students, in which LTBI was diagnosed and pharmacologically treated by lung specialist.
Discussion
As expected, only 8 students were positive for both tests, confirming the low prevalence of TB in Italian population. The screening among students allowed identifying LTBI in a young population, presumably a few years from infection. According to international guidelines, among healthcare workers a “two-step strategy” could be more economically justified than other methods. However, QFT-G should be performed at no more than 3 days after a TST, because this approach may be limited by TST-mediated boosting of subsequent QFT-G responses.