Chest CT scan as an initial diagnostic method for tuberculosis infection detected by mass screening in the intermediate-burden country

<b>Backgrounds:</b> The first step in diagnosing latent tuberculosis (TB) in patients with confirmed TB infection is to exclude active TB. The currently recommended test for this is chest X-ray (CXR), with limited data on whether computed tomography (CT) can be a better alternative. We aimed to elucidate a diagnostic yield of CT as an initial diagnostic method for patients with TB infection confirmed by mass screening in a country with intermediate burden of TB. <b>Methods:</b> A retrospective study was conducted on patients who were identified as TB infection with tests conducted as a part of mass screening test in South Korea from January 2015 to March 2018. They were classified according to whether they had a CXR or CT as an initial diagnostic test to exclude TB. Detection rate of active TB and implementation rate of further procedures were compared between each group. <b>Results:</b> Of 542 patients with TB infection confirmed by mass screening, 222 and 320 patients were initially examined by a CXR and CT, respectively. The detection rate of active TB was not different according to initial radiologic method (CXR vs. CT, 0.9% vs. 2.5%; P=0.300). However, bronchoscopy (CXR vs. CT, 1.4% vs. 6.6%; P=0.007) and TB PCR test (CXR vs. CT, 1.8% vs. 7.8%; P=0.004) were performed significantly more in the CT group than CXR group. <b>Conclusion:</b> CT was not supported as an initial diagnostic method to rule out active TB in patients with TB infection confirmed by mass screening in an intermediate-burden country, because it did not show difference in detecting active TB despite increasing further invasive tests.