The objective was to assess the global oral lichen planus prevalence. We searched PubMed, EMBASE, Web of Science, and Scopus for studies published before September 2019. We evaluated the quality of studies and carried out several meta-analyses. The global pooled prevalence was 1.01%, with a marked geographical difference (p < .001). The highest prevalence was reported from Europe (1.43%) and the lowest in India (0.49%), where tobacco-associated keratosis appears to mask oral lichen planus resulting in attenuation of its prevalence. From the age of 40 years, the prevalence increases significantly and progressively (OR = 3.43, 95% CI = 2.48-4.73, p < .001). Studies that define diagnostic criteria report a higher prevalence (1.31% vs. 0.70%, p = .03), although the application of the WHO criteria (year 1978-2007) does not increase the ability to diagnose the disease compared with other criteria (p = .11). The studies performed by oral medicine/oral pathology specialists report significantly higher prevalence (1.80%) than dentists (0.61%) and dermatologists (0.33%; p < .001). In conclusion, we propose that reliable diagnostic criteria should be defined, which should include a set of essential criteria including the presence of white reticular lesions in any location of the oral mucosa. The impact of histopathological confirmation with defined diagnostic criteria must be researched in the future, although its main use should be to determine the presence or absence of epithelial dysplasia. The necessity to improve the knowledge of oral lichen planus among dentists and dermatologists through continuing education is apparent in the results of this meta-analysis.
Keywords: malignant transformation; meta-analysis; oral cancer; oral lichen planus; prevalence; systematic review.
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