The PBC Foundation is the only UK organisation exclusively dedicated to providing support and information to those affected by PBC
There are three investigations upon which the diagnosis of PBC is based.
The Antimitochondrial Antibody (AMA)
These antibodies, usually detected by indirect immunofluorescence, are now known to be directed against a group of enzymes – the pyruvate dehydrogenase complex – normally found on the inner mitochondrial membrane of almost all animal cells. These antibodies are very disease specific, but are neither tissue, nor species, specific. They are present in around ninety percent of patients with PBC. It has been shown that individuals with a consistent strongly positive antimitochondrial antibody in the serum at a titre of <1:40, but who have normal liver function tests, have a high probability of having abnormal liver histology suggestive of early PBC. Over eighty percent of these individuals will develop biochemical and clinical features of the disease.
Liver Function Tests
Patients with PBC have abnormal liver function tests, usually the alkaline phosphatase is more raised than the transaminases. Serum bilirubin is elevated late in the disease. Liver synthetic function is preserved until late in the disease, so serum albumin and clotting are usually normal. Immunoglobins show raised serum IgM, often IgG.
The classical lesion of PBC is an immune attack upon intrahepatic bile ducts with aggregates of lymphocytes, sometimes with non-caseating granulomas, near bile ducts. As the disease progresses, there is piecemeal necrosis of liver cells extending from portal tracts together with portal fibrosis. This leads to a combination of disappearing bile ducts and, ultimately, cirrhosis. The pathological process can be uneven within the liver. Liver biopsy is very helpful for staging the disease.
The staging of the liver disease is assessed by the clinical, serological, image findings and liver histology. Liver ultrasound may be used to exclude concomitant gallstone disease, particularly in patients with abdominal discomfort. Furthermore, use of Fibroscan and serological markers of fibrosis will also give useful and non-invasive help in determining the degree of fibrosis. In practice, if a middle-aged female has positive antimitochondrial antibodies and is found to have raised serum alkaline phosphatase, then the likelihood is extremely high that she has PBC, even in the absence of any symptoms related to liver disease. If, during the investigation of any other disease, a patient is found to have positive antimitochondrial antibodies, then liver function tests should be checked and specific clinical enquiries should be made of the patient concerning the possibility of PBC symptoms.