Active Case Finding Using Mobile Chest x-ray among Homeless People with Pulmonary Tuberculosis in Osaka City, Japan, 2013-2019.

Mobile digital chest x-ray (CXR) is a commonly used method for pulmonary tuberculosis (PTB) screening among homeless people in the Nishinari District, Osaka City, Japan. We investigated mobile CXR screening (MCS) to calculate the case finding rate of culture-confirmed PTB among homeless examinees in the Nishinari District from 2013 to 2019. PTB was defined by sputum culture-confirmed cases. Examinees with culture-confirmed PTB more than 90 days after MCS were defined as no progression to active tuberculosis when undergoing MCS. We collected participants' information including their name, date of birth, age, sex, date of MCS, CXR classification (whether abnormal CXR required further investigation), date of PTB diagnosis, and sputum smear results. Of 10,111 homeless people, 175 (1.7%) participants with abnormal CXR underwent further investigation at medical facilities. Of those with abnormal CXR, 22 (0.22%) were diagnosed as culture-positive PTB within 90 days of MCS. Of 22 PTB with culture-positive results, 13 (59.1%) PTB were smear-positive. We found that MCS contributed to detect PTBs with the lower smear positive rate among patients with PTB analyzed by MCS compared with all culture-confirmed PTB in the Nishinari District.