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Table 1 Seven proposed COVID-19 CT severity score systems

From: CT severity score in COVID-19 patients, assessment of performance in triage and outcome prediction: a comparative study of different methods

CTSSs Segmentation Severity Score for each segment Maximum Score
CTSS1 [2, 3] Three zones in each lung are divided by carina and lower pulmonary vein 1–4 according to percentage of involvement (< 25, 25–49, 50–74, > 75) 24
CTSS2 [4] The same zonal concept as CTSS1 with additional division of each zone into anterior and posterior regions divided by midpoint of diaphragm antero-posteriorly 1–4 according to percentage of involvement (< 25, 25–49, 50–74, > 75) 48
CTSS3 [5, 6] Five anatomic lobes of the lungs 1–4 according to percentage of involvement (< 25, 25–49, 50–74, > 75) 20
CTSS4 [7, 8] Five anatomic lobes of the lungs 1–5 according to percentage of involvement (< 5, 5–25, 25–49, 50–74, > 75) 25
CTSS5 [9] Five anatomic lobes of the lungs 1–4 according to the diameter of the largest lesion in each lobe (< 1 cm, 1-3 cm, > 3 cm up to 50% of the lobe, > 50% of a lobe 20
CTSS6 [10] 18 anatomic segments of the lung with an additional division of apico-posterior segment of the left upper lobe into apical and posterior divisions and anteromedial segment of the left lower lobe into anterior and medial segments No involvement = 0
 < 50% involvement = 1
 ≥ 50% involvement = 2
40
CTSS7 [current authors] Five anatomic lobes of the lungs with additional consideration of the lingula as a separate lobe 1–5 according to percentage of involvement (< 5, 5–25, 25–49, 50–74, > 75) 30