CT Chest Severity Score for COVID 19 Pneumonia: A Quantitative Imaging Tool for Severity Assessment of Disease

OBJECTIVE: To determine a cut-off value of Chest CT severity score (CT-SS) in order to discriminate between the clinical types of COVID-19 pneumonia. STUDY DESIGN: Observational study. PLACE AND DURATION OF STUDY: Department of Radiology, Shifa International Hospital, from 1st March to June 30th, 2020. METHODOLOGY: One hundred and three consecutive patients' RT PCR positive for COVID-19 were included. Two consultant radiologists, with experience of 7 to 10 years in body imaging, evaluated their HRCT studies in consensus and calculated the CT severity score. A scoring of all 20 individual regions in each lung were assigned by the radiologists attributing a score of 0, 1 or 2 to each region, if parenchymal opacification was none, less than 50%, or 50% or more, respectively. The CT severity score was a summation of scores of all 20 regions of both lungs combined with a range of 0 to 40 points. The scores were compared for clinically mild and severe disease. RESULTS: Significant differences were noted regarding the scoring of lung opacity in mild and severe groups in each lung segment, p <0.05. The most significantly involved segments were right lower lobe's medial and lateral basal segment, left upper lobe's superior lingular segment and left lower lobe's medial basal and lateral basal segments. To discriminate mild versus severe disease, CT-SS threshold value turned out to be 19.5 Conclusion: CTSS may be of value for a prompt and objective means of assessing the degree of severity and disease burden in lungs. Key Words: COVID-19, COVID-19 diagnosis, Pneumonia, Novel coronavirus, CT severity score, Respiratory tract infection, Triage, Pandemic, RT-PCR, SARS-COV 2, Outbreak.