CROSS-SECTIONAL STUDY OF OPISTHORCHIS-VIVERRINI INFECTION AND CHOLANGIOCARCINOMA IN COMMUNITIES WITHIN A HIGH-RISK AREA IN NORTHEAST THAILAND

We describe an innovative strategy to quantify risk of cancer associat ed with varying levels of exposure to chronic parasitic infection thro ugh the identification of asymptomatic cases of cholangiocarcinoma wit hin a population-based survey of Opisthorchis viverrini infection. Sto ol samples from 12,311 adults over age 24 years from 85 villages in no rtheast Thailand were examined for intensity of liver fluke infection. People from varying egg count categories were selected for ultrasound examination to identify hepatobiliary disease. Fifteen preclinical ca ses of cholangiocarcinoma were diagnosed from a total of 1,807 people based on ultrasonographic evidence with confirmation by endoscopy wher e possible. The prevalence odds of the diagnosis of cholangiocarcinoma increased gradually within the light and moderate intensity groups. I n contrast, sharply elevated prevalence odds [age-, sex- and locality- adjusted prevalence odds ratio (FOR) 14.1, p < 0.05] were observed wit hin the most heavily liver fluke-infected group compared with the unin fected group. Males were more frequently affected than females (crude FOR 4.5), but after controlling for intensity of infection, age and lo cality, the magnitude and significance of this measurement was reduced . Our data clearly demonstrate a significant relationship between inte nsity of liver fluke infection and cholangiocarcinoma and a strikingly high prevalence of the disease among heavily infected males. (C) 1994 Wiley-Liss, Inc.