[Can an individual with a positive baseline QuantiFERON test result develop active tuberculosis?].

OBJECTIVES

QuantiFERON-TB Gold (QFT-G) test has been recommended as a new tool for the diagnosis of latent tuberculosis (TB) infection. However, the risk of development of active TB in the future depends on the period after the infection. The aim of this study was to evaluate the risk of development of active TB in individuals who have been infected.

METHODS

Clinical development of TB in subjects with positive baseline QFT test results was retrospectively analyzed. The subjects included healthcare workers, since 2003, at the Fukujuji Hospital who were examined at employment.

RESULTS

In total, 667 subjects were examined using the QFT-2G test, and 62 subjects were QFT positive at the first examination. One was treated using isoniazid, and 61 subjects were followed up for an average of 4.7 years (286 person-years). None of the subjects developed active TB during the observation period, and the probability of clinical breakdown (95% confidence interval) was 0-0.0104/person-year.

CONCLUSION

The risk of development of active TB among subjects with positive QFT-G test results at baseline was low. Treatment of latent TB infection is not recommended, unless an individual has been recently infected.