Table 3. Diagnostic performance of different rCT values, size of the nodule and their combination in distinguishing between pre-invasive and invasive adenocarcinoma appearing as pure GGNs.

Variable	Cut-off value	Sensitivity	Specificity	AUC (95% CI)
rCT value 1 (HU)	293.82	58.0%	94.7%	0.783 (0.69–0.88)
rCT value 2	0.68	89.5%	58.0%	0.742 (0.63–0.85)
Mean size (cm)	1.10	74.0%	79.0%	0.796 (0.68–0.90)
rCT 1-size	NA	62.5%	89.5%	0.795 (0.70–0.89)
rCT 2-size	NA	71.6%	89.5%	0.845 (0.76–0.93)

rCT 1/2-size: combining relative CT value and mean size. AUC, area under the curve; CT, computed tomography; GGN, ground-glass nodule; HU, Hounsfield units.