ThinPrep® Whole-Slide Digital Images versus Conventional Microscopy in Negative for Intraepithelial Lesion or Malignancy, Atypical Squamous Cells of Undetermined Significance, and Low-Grade Squamous Intraepithelial Lesion Cervical Lesions: European Federation of Cytological Societies (EFCS) Study

Abstract – Introduction: High inter- and intraobserver variability is acknowledged in negative for intraepithelial lesion or malignancy (NILM), atypical squamous cells of undetermined significance (ASC-US), and low-grade squamous intraepithelial lesion (LSIL) diagnostic categories in cervical cytology. As digital cytology has emerged, whole-slide images (WSIs) have been compared to conventional light microscopy (LM) to evaluate its feasibility in routine practice. Methods: Six cytopathologists evaluated 20 liquid-based cervical samples diagnosed as ASC-US, LSIL, or NILM with known hrHPV status, both by conventional LM and WSI, equalling 240 evaluations. Interobserver agreement was measured using Fleiss’s kappa, Kendall´s coefficient and interclass correlation (ICC). Results: Most of the samples (93.75%) were assigned to the same original range of categories: NILM 5 (25%), ASC-US 10 (50%), and LSIL 5 (25%). WSI versus LM interobserver agreement varied with Fleiss’s kappa (0.324 versus 0.319), Kendall’s W (0.670 versus 0.572), and ICC (0.585 versus 0.414). Interobserver agreement for the ASC-US category was higher in Kendall’s W (0.435 for WSI versus 0.329 for LM) and in ICC (0.394 versus 0.118). Fleiss’s kappa showed lower interobserver agreement for ASC-US in WSI than LM (0.000 versus 0.039). Conclusion: This study illustrated that despite overall better agreement in WSI, ASC-US results were less favourable in WSI than LM, according to Fleiss’s kappa test, but not other tests.