Background The prevalence of Behçet's disease (BD) is much higher in countries along the ancient Silk Route, extending from Japan to Mediterranean countries including Turkey, than in northern Europe and the USA. Three previous epidemiologic surveys have been carried out in different regions of Turkey.
Patients and methods This study investigated the cross-sectional prevalence of BD in individuals aged > 12 years in Istanbul, Turkey, in two stages. The first stage aimed to identify individuals with recurrent oral ulcers (ROUs) by visiting them in their homes, and the second stage aimed to further examine those with ROUs for the presence of other BD-related manifestations under hospital conditions. The sample size was determined to be 24,000 with an expected BD prevalence rate of 1/1000 and a sampling error of 4/10,000, with a 95% confidence interval (CI) of 6–14/10,000. The number of individuals to be screened in each district was determined in proportion to the population of all districts in Istanbul.
Results The standard questionnaire was applied to a total of 23,986 individuals at their homes. A history of ROU was recorded in 2289 individuals (9.5%), and a previous diagnosis of BD was recorded in 47. The diagnosis of ROU was confirmed in 700, and the diagnosis of BD was established in 101 according to the International Study Group criteria. The prevalence rate of BD was estimated as 42/10,000 (95% CI, 34–51/10,000) in Istanbul, Turkey.
Conclusions This survey conducted in Istanbul, the largest cosmopolitan city in Turkey with immigrants from all over the country, has a larger sample size than other previous studies, and therefore the reported prevalence rate of BD has a more acceptable confidence interval. This study aids in the estimation of the prevalence of BD in Turkey, and supports previous findings that Turkey has the highest prevalence rate of the disease in the world.