Epidemiology improves our knowledge of disease

Recent epidemiological and clinical research is changing our thinking on primary biliary cirrhosis, a chronic cholestatic liver disease probably of autoimmune origin. Until the early 1970s primary biliary cirrhosis was perceived as a disease that was rare, presented with persistent jaundice, and usually progressed to death from liver failure.1 Epidemiological and clinical research based on both registers of cases in defined populations and, more commonly, clinical case series has transformed that picture. The disease is much commoner than was believed,2 3 4 as many as half of all patients may have no symptoms of liver disease at diagnosis,5 and both the onset of complications and death can be delayed by treatment with ursodeoxycholic acid6 and, when necessary, liver transplantation. Good clinical and health care strategies will depend on further integration of epidemiological and clinical research to provide better information on the frequency and natural course of the disease and to generate hypotheses about causation.

For both epidemiological and clinical purposes a widely accepted and validated case definition is necessary. In primary biliary cirrhosis the triad of results from liver function tests …