Utility of screening chest radiographs in patients with asymptomatic and mildly symptomatic COVID-19 at a field hospital in Samut Sakhon, Thailand

Background: In a new episode of the COVID -19 pandemic in Thailand during the beginning of 2021, cases in Samut Sakhon Province mainly occurred in foreign workers and were mostly asymptomatic or had mild disease. To prevent overwhelming the local hospital, a field hospital was established which used chest radiography as one of screening tools for triaging patients. Objective: To determine the clinical utility of chest radiographs as a screening tool for COVID-19 patients who were asymptomatic or mildly symptomatic. Materials and Methods: Six hundred nineteen patients with COVID -19 (confirmed by reverse transcriptase-polymerase chain reaction) were registered at the field hospital at Samut Sakhon provincial sport stadium during 5-8 January 2021 and had chest radiographs taken. The image readings were based on the consensus of two radiologists and a final decision was made by a third radiologist if the first two did not agree. Findings on chest radiographs and clinical outcomes were evaluated. Results: The study included 619 radiographs; 328/619 (53%) men and 291/619 (47%) women had a mean age of 33.3+/- 9.7 (range, 5-64) years. There was mild disease in 13/619, and asymptomatic infections in 606/619.  Chest radiographs were normal in 568 (91.7%) and abnormal in 51 (8.3%) patients; typical findings of COVID-19 were seen in 3 (0.5%) patients. Other abnormal findings were found in 23 (3.8%) patients such as active tuberculosis in 6 (1.0%). Four patients were transferred to the hospital, one of whom required supplemental oxygen.  Conclusion: Combined chest radiographic and clinical information allows better decisions regarding hospital transfers of asymptomatic and mildly symptomatic COVID-19 patients at a field hospital.