Diagnostic Power of Chest CT for COVID-19: To Screen or Not to Screen

Background: Chest CT is increasingly used for COVID-19 screening in healthcare systems with limited SARS-CoV-2 PCR capacity. Its diagnostic value was supported by studies with methodological concerns and its use is controversial. Here we investigated its potential to diagnose COVID-19 in symptomatic patients and to screen asymptomatic patients in a prospective study with minimal selection bias. Methods: From March 19, 2020 to April 20, 2020 we performed parallel SARS-CoV-2 PCR and CT with categorization of COVID-19 suspicion by CO-RADS, in 859 patients with COVID-19 symptoms and 1138 controls admitted to the hospital for COVID-19 unrelated medical urgencies. CT-CORADS was categorized on a 5-point scale from 1 (very low suspicion) to 5 (very high suspicion). AUC under ROC curve were calculated in symptomatic versus asymptomatic patients to predict positive SARS-CoV-2 positive PCR and likelihood ratios for each CO-RADS score were used for rational selection of diagnostic thresholds. Findings: CT-CORADS had significant (P<0·0001) diagnostic power in both symptomatic (AUC=0·891) and asymptomatic (AUC=0·700) patients hospitalized during SARS-CoV-2 peak prevalence. In symptomatic patients (41·7% PCR+), CO-RADS ≥ 3 detected positive PCR with high sensitivity (89·1%) and 72·5% specificity. In asymptomatic patients (5·3% PCR+), a CO-RADS score ≥ 3 detected SARS-CoV-2 infection with low sensitivity (45·0%) but high specificity (88·8%). Interpretation: CT-CORADS has meaningful diagnostic power in symptomatic patients, supporting its application for time-sensitive triage. Sensitivity in asymptomatic patients is insufficient to justify its use as screening approach. Incidental detection of CO-RADS ≥ 3 in asymptomatic patients should trigger reflex testing for respiratory pathogens. Funding Statement: This work was supported by a donation from board members of Fagron (Nazareth, Belgium), a healthcare company, to RADar, the teaching and education initiative of AZ Delta General Hospital, to be used as unconditional research grant for data collection, collaborative collaboration and open access publication. Declaration of Interests: The authors declare no conflict of interest. Ethics Approval Statement: The study was approved by the AZ Delta Institutional Review Board with a waiver of informed consent from study participants considering the study is based on secondary analysis of existing data (Clinical Trial Number: B1172020000008).