Epidemiological study of oral leukoplakia based on mass screening for oral mucosal diseases in a selected Japanese population.

The purpose of this study was 1) to show the epidemiological status of oral leukoplakia in a selected population of 3131 Japanese (504 women, 2627 men, aged 18-63 yr, mean age 35.9 yr), and 2) to estimate of the validity of the diagnosis of oral leukoplakia by general practitioners. Seventy-seven individuals were detected as having leukoplakia, a prevalence of 2.5%; 2.7% and 1.0% for men and women, respectively, a difference that is statistically significant (P less than 0.001). The percentage of smokers was 75.3% for patients with leukoplakia and 47.8% for individuals detected as not having leukoplakia, a difference which is statistically significant (P less than 0.001). Of 77 leukoplakia patients, 37 cases (48.1%) received a clinically confirmed diagnosis and 27 patients were diagnosed in further examination as having leukoplakia. These results can also be expressed by a positive predictive value of 0.73 and a false positive ratio of 0.27 for the diagnosis of leukoplakia in the primary mass screening by general practitioners. The results of this study suggest that in order to carry out an efficient oral health program in Japan, the objects for mass screening for leukoplakia might be better limited to men over 30 and women over 40 yr of age.