Leukoplakia prevalence estimate lower than expected

Data were sourced using Medline and Embase.

Initial selection criteria were that study samples should be representative of the underlying adult population and that the leukoplakia diagnostic criteria used by the examiners should have been widely accepted ones. Because most published studies did not comply with these requisites, modified criteria were as follows. First, the sample, even if not representative of the underlying study population, should not have been collected from surgical departments of dental hospitals or clinics, where leukoplakia is usually treated (these studies would overestimate the disease prevalence). Secondly, even if the examiners were not calibrated, the diagnostic criteria used should be consistent with the internationally accepted criteria and must have been reported in the text. Thirdly, to make statistical analysis possible even if leukoplakia prevalence was not reported as a proportion, the overall number of sampled subjects and the number with the condition must be easy to extrapolate with a high level of accuracy.

Data were pooled using inverse variance weighting and random-effect methods. A sensitivity analysis was performed.

A total of 23 primary studies was included, giving point-prevalence estimates with the inverse variance method of 1.49% [95% confidence interval (CI), 1.42-1.56] and 2.60% (95% CI, 1.72-2.74) with the random-effects method. The high between-study heterogeneity and the sensitivity analyses suggested that the second estimate was more reliable. Leukoplakia was significantly more prevalent in males (prevalence ratio, 3.22), but no difference was found between geographical areas and between younger and older adults. Using these data, the crude annual oral cancer incidence rate attributable to leukoplakia would be between 6.2 and 29.1 cases per 100 000 people.

The pooled leukoplakia prevalence estimate was lower than expected. The estimated oral cancer incidence rate due to leukoplakia malignant transformation was high, however, and suggested that the global number of oral cancer cases is probably under-reported, particularly in developing countries.