Grading systems of oral cavity pre-malignancy: a systematic review and meta-analysis

Oral potentially malignant disorders (OPMDs) may have varying degrees of oral epithelial dysplasia (OED). Traditional grading schemes separate OED into three-tiers (mild, moderate, and severe). Alternatively, a binary grading system has been previously proposed that stratifies OED into low-risk and high-risk categories based on a quantitative threshold of dysplastic pathologic characteristics. This systematic review evaluates the predictive value of a binary OED grading system and examines agreement between pathologists.

This meta-analysis queried 4 databases (PubMed, Ovid-MEDLINE, Cochrane, and SCOPUS) and includes 4 studies evaluating binary OED grading systems. Meta-analysis of proportions and correlations was performed to pool malignant transformation rates (MTR), risk of malignant transformation between OED categories, and measures of interobserver agreement.

Pooled analysis of 629 lesions from 4 different studies found a six-time increased odds of malignant transformation in high-risk lesions over low-risk lesions [odds ratio (OR) 6.14, 95% 1.18-15.38]. Reported ORs ranged from 2.8 to 22.4. The overall MTR was 26.8%, with the high-risk and low-risk lesions having MTRs of 57.9% (95% CI 0.386-0.723) and 12.7% (95% CI - 0.210 to 0.438), respectively. Pooled unweighted interobserver kappa values for the binary grading system and three-tiered system were 0.693 (95% CI 0.640-0.740) and 0.388 (95% CI 0.195-0.552), respectively.

Binary grading of OED into low-risk and high-risk categories may effectively determine malignant potential, with improved interobserver agreement over three-tiered grading. Improved grading schemes of OED may help guide management (watchful waiting vs. excision) of these OPMDs.