Pooled estimate of world leukoplakia prevalence: a systematic review.

This study was aimed at estimating the pooled global leukoplakia prevalence using both well-designed studies, which were too few to be representative of the world situation, and less valuable studies. The inverse variance weighting and the random effect methods were used. The latter is based on the principle that if primary studies are heterogeneous, the between-study variance is higher than zero, and its effect must be taken into account in choosing the weighting scheme. The robustness of the estimates was assessed by means of sensitivity analyses. Including 23 primary studies from all over the world published between 1986 and 2002, the point estimates were 1.49% (inverse variance, 95% confidence interval 1.42%-1.56%) and 2.60% (random effect, 95% confidence interval 1.72%-2.74%). The high between-study heterogeneity and the sensitivity analyses suggested that the second estimate was more reliable. Leukoplakia was significantly more prevalent among 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 per 100000, thus suggesting that the global number of oral cancer cases is probably underreported.