Intra-observer and inter-observer variability in two grading systems for oral epithelial dysplasia: A multi-centre study in India

Background The presence and grading of oral epithelial dysplasia (OED) are considered the gold standard for predicting the malignant risk of oral potentially malignant disorders. However, inter-observer and intra-observer agreement in the context of reporting on OED grading has been reputedly considered unreliable. Methods We undertook a multi-centre study of six Indian oral pathologists to assess variations in reporting OED using the World Health Organization (WHO; 2005) system and also the recently introduced binary system. The observer variability was assessed with the use of kappa statistics. Results The weighted kappa intra-observer agreement scores improved (kappa(w) = 0.5012) on grouping by two grades as no and mild dysplasia versus moderate and severe dysplasia compared to binary grading system (kappa = 0.1563) and WHO grading system (kappa(w) = 0.4297). Poor to fair inter-observer agreement scores were seen between the principal investigator (PI) and the other five observers using the WHO grading system (kappa = 0.051-0.231; kappa(w) = 0.145 to 0.361; 35% to 46%) and binary grading system (kappa = 0.049 to 0.326; 50 to 65%). Conclusions There is considerable room for improvement in the assessment of OED using either system to help in standardised reporting. The professional pathology organisations in India should take steps to provide external quality assessment in reporting OED among oral and general pathologists who are engaged in routine reporting of head and neck specimens.