Sources of interobserver variation in histopathological grading of cervical dysplasia

The present study aimed to assess where the interobserver variation in grading cervical dysplasia stems from. Four experienced pathologists examined 93 histological slides, after they agreed on which morphological characteristics should be considered relevant for grading. They scored 6 morphological characteristics for each slide and assigned it to a degree of dysplasia. Compared to a previous study, the interobserver variation showed a statistically significant improvement: the weighted group kappa value increased from 0.55 to 0.69. For the scores of the individual characteristics considerable interobserver variation was observed: weighted group kappa values ranged from 0.28 to 0.49. The pathologists slightly differed in which characteristics they considered most important for their grading. The agreement on the degree of dysplasia turned out to be better than the agreement on the morphological characteristics on which this diagnosis is based. In the discussion, a few explanations for this paradoxical finding are put forward.