The geoepidemiology of primary biliary cirrhosis

There are apparently large geographical and secular variations in the prevalence of primary biliary cirrhosis worldwide. Most studies suggest that the disease is most common in Northern Europe, particularly northern Britain and Scandinavia, and that the prevalence is increasing. This comprehensive review of the literature explores to what extent these variations could be real rather than artifactual due to lack of comparability among studies. The major design flaws are examined and guidelines for better practice are outlined. It is hoped that other researches will utilize these recommendations for future studies so that true variations can be identified and hypotheses regarding disease causation may be formulated and investigated. These guidelines include: stringent case inclusion criteria; definition of date of disease onset; well-defined study period, area and population; multiple case finding methods; rigorous tracing of all possible cases. Preliminary results of the authors' study using these guidelines are described and report a point prevalence of 235 per million population in 1994 in the north of England, the highest yet reported.