Diameter thresholds for pure ground-glass pulmonary nodules at low-dose CT screening: Chinese experience

Background Limited research exists on screening thresholds for low-dose CT in detecting malignant pure ground-glass lung nodules (pGGNs) in the Chinese population. Materials and methods A retrospective analysis of the Guangzhou Lung-Care programme was conducted, retrieving average transverse diameter, location, histopathology, frequency and follow-up intervals. Diagnostic performances for ‘lung cancers’ were evaluated using areas under the curve (AUCs), decision curve analysis (DCA), sensitivities and specificities, with thresholds ranging from 5 mm to 10 mm. We divide malignant pGGNs into three groups: (1) minimally invasive adenocarcinoma (MIA) and invasive adenocarcinoma (IA), (2) atypical adenomatous hyperplasia (AAH) and adenocarcinoma in situ (AIS) and MIA and IA and (3) IA-only. Results In ‘MIA+IA’, increasing the threshold from 5 mm to 8 mm improved specificity (60.97% to 88.85%, p<0.001) and positive predictive values (PPVs; 5.87% to 14.88%, p<0.001), but decreased sensitivity (94.44% to 75.56%, p<0.001). Further raising threshold from 8 mm reduced sensitivity (75.56% to 60.00%, p<0.001), while slightly increasing specificity (88.85% to 93.47%, p<0.001) and PPVs (14.88% to 19.15%, p<0.001). Increasing threshold from 5 mm to 7 mm enhanced the AUC for ‘MIA+IA’ (from 0.711 to 0.829), ‘AAH+AIS+MIA+IA’ (from 0.748 to 0.804) and ‘IA-only’ (from 0.783 to 0.833). At 8 mm, the AUCs for these categories were similar. However, increasing the threshold from 7 mm to 10 mm resulted in reduced AUCs for ‘MIA+IA’ (0.829 to 0.767), ‘AAH+AIS+MIA+IA’ (0.804 to 0.744) and ‘IA-only’ (0.833 to 0.800). DCA reveals that the 8 mm predictive model demonstrates greater clinical utility compared with models with other thresholds. Conclusions Increasing the diameter threshold for positive results for pGGNs, up to 8 mm could enhance diagnostic performance. Trial registration number NCT04938804 .