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

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