Chest x-ray or CT for COVID-19 pneumonia? Comparative study in a simulated triage setting.

INTRODUCTION: for the management of patients referred to respiratory triage during the early stages of the SARS-CoV-2 pandemic, either chest radiograph (CXR) or computed tomography (CT) were used as first-line diagnostic tools. The aim of this study was to compare the impact on triage, diagnosis and prognosis of patients with suspected COVID-19 when clinical decisions are derived from reconstructed CXR or from CT. METHODS: we reconstructed CXR (r-CXR) from high-resolution CT (HRCT) scan. Five clinical observers independently reviewed clinical charts of 300 subjects with suspected COVID-19 pneumonia, integrated with either r-CXR or HRCT report in two consecutive blinded and randomised sessions: clinical decisions were recorded for each session. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and prognostic value were compared between r-CXR and HRCT. The best radiological integration was also examined to develop an optimised respiratory triage algorithm. RESULTS: interobserver agreement was fair (Kendall's W=0.365; p<0.001) by r-CXR-based protocol and good (Kendall's W=0.654; p<0.001) by CT-based protocol. NPV assisted by r-CXR (31.4%) was lower than that of HRCT (77.9%). In case of indeterminate or typical radiological appearence for COVID-19 pneumonia, extent of disease on r-CXR or HRCT were the only two imaging variables that were similarly linked to mortality by adjusted multivariable models CONCLUSIONS: the present findings suggest that clinical triage is safely assisted by CXR. An integrated algorithm using first-line CXR and contingent use of HRCT can help optimise management and prognostication of COVID-19.