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.