Real-world evaluation of a computed tomography-first triage strategy for suspected coronavirus disease 2019 in emergency outpatients in Japan: an observational cohort study

Background: Coronavirus disease 2019 (COVID-19) continues to spread worldwide. Because of the absence of reliable rapid diagnostic systems, patients with COVID-19 symptoms are suspected of disease. Computed tomography (CT) in patients with suspected COVID-19 may be reasonable for triaging, and CT-first triage strategies have been proposed. However, clinical evaluation of a CT-first triage protocol is lacking. The aim of this study is to investigate the real-world efficacy and limitations of a CT-first triage strategy in patients with suspected COVID-19.Methods: This was a single-center cohort study evaluating outpatients with suspected COVID-19 who underwent a medical examination at Yokohama City University Hospital and who were prospectively registered between 9 February and 5 May 2020. We treated patients according to the CT-first triage protocol. CT findings were classified into five categories according to the COVID-19 Reporting and Data System (CO-RADS). With the CT-first triage protocol, patients with a suspicious clinical history, symptoms, or suspicious findings on chest CT were allocated to the COVID-19 suspected group. The primary outcome was efficacy of the CT-first triage protocol for outpatients with suspected COVID-19. We conducted additional analyses of the isolation time of outpatients with suspected COVID-19 and reached final diagnoses.Results: In total, 108 outpatients with suspected COVID-19 were examined at our hospital. Forty-eight patients (44.9%) were categorized as CO-RADS 1, 26 patients (24.3%) as CO-RADS 2, 14 patients (13.1%) as CO-RADS 3, 6 patients (5.6%) as CO-RADS 4, and 13 patients (12.1%) as CO-RADS 5. One patient was excluded because of pregnancy. Using the CT-first triage protocol, 48 (44.9%) patients were suspected of having COVID-19. Nine patients (18.8%) in this group were positive for severe acute respiratory syndrome coronavirus 2 using polymerase chain reaction; no patients in the group not suspected of having COVID-19 were diagnosed with COVID-19 during follow up. The protocol significantly shortened the duration of isolation for the not-suspected versus the suspected group (70.5 vs. 1037.0 minutes, P < .001). Conclusions: Our CT-first triage protocol was acceptable for triaging outpatients with suspected COVID-19. This protocol will be helpful for appropriate triage, especially in areas where polymerase chain reaction is limited.