Interobserver and intraobserver variability in the histopathologic assessment of oral lichen planus based on modified WHO criteria

In 1978 WHO (World health organization) formulated a histopathological definition for diagnosis of OLP (oral lichen planus). Previous studies showed that diagnosis of OLP with these criteria are not reproducible. In 2003 Van der Meij et al. represented new clinical and histopathologic definition for diagnosis of OLP known as modified WHO criteria. The purpose of this study was to evaluate the interobserver and intraobserver variability in the histopathological assessment of OLP based on the modified WHO criteria.
Fifty five microscopic slides which OLP and OLL (Oral Lichenoid Lesion) were recognized in their clinical differential diagnosis were given to 6 pathologists in two phases with 3 months interval. Each reviewing pathologist was asked to apply the modified WHO definition of OLP and to categorize each case as either OLP, or compatible with OLP. Then, the interobserver and intraobserver variability were assessed by calculation of repeatability coefficient and Kappa statistics.
The results of this study demonstrated that interobserver variability based on modified WHO criteria was 0.77 (strong), while the intraobserver variability varied from 0.58 (moderate) to 0.82 (strong).
In the present study, the interobserver and intraobserver variability in the histopathologic assessment of OLP based on modified WHO criteria was stronger than previous studies which assessed WHO criteria. However, in order to propose the replacement of WHO criteria with modified WHO criteria, further studies with more cases and comparing the two methods is required.