Interobserver and intraobserver variability in the clinical assessment of oral lichen planus.

Background: In 1978, a clinical definition of OLP was formulated by the WHO. To date, the validation results of this clinical definition have not been published. The aim of this study was to evaluate interobserver and intraobserver variability in the clinical assessment of oral lichen planus (OLP).

Methods: Four clinicians examined a set of 159 clinical pictures of a white lesion in a group of 60 patients. Each reviewing examiner was asked to apply the WHO definition of OLP from 1978, and to categorise each case as either: (i) diagnostic of OLP, (ii) other definable lesion, or (iii) leukoplakia. After three months, each of the four reviewing clinicians was given the clinical pictures of 45 randomly retrieved cases from the original 60. Interobserver and intraobserver variability were assessed by calculation of unweighted kappa statistics.

Results: Interobserver agreement varied from 0.43 (moderate) to 0.77 (substantial), while the intraobserver agreement varied from 0.62 (substantial) to 0.92 (good).

Conclusions: Although the clinical WHO definition of OLP seems to be more reproducible than the histopathological one, there is still a significant amount of subjectivity in using this definition. A set of clinical and histopathological diagnostic criteria with good interobserver and intraobserver agreements (kappa values > 0.8) is very important in enabling reproducible and reliable studies on OLP to be performed.