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Diagnosis of Primary Biliary Cholangitis

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Primary Biliary Cholangitis

The diagnosis of primary biliary cholangitis usually rests on the liver tests and the autoantibody profile rather than on a liver biopsy.

Diagnosis

PBC should be suspected when a patient has cholestatic laboratory or clinical findings that have run a chronic course, for longer than 6 months. When that pattern is present, the workup proceeds in steps:

  1. history, physical examination and abdominal ultrasound — ultrasound is done first to look for a dilated biliary tract, which would point to gallstones or another obstruction rather than to PBC.
  2. AMA and ANA testing — if these are negative,
  3. extended imaging such as MRCP — if this is also unrevealing,
  4. liver biopsy.

The diagnosis is confirmed when at least 2 of the following 3 criteria are met in the patient:

  • Chronic elevation of the liver tests, mainly alkaline phosphatase at least 1.5 times the upper limit of normal. Almost all patients with PBC have raised ALP and GGT. ALT and AST are usually only mildly raised, less than 3 times the upper limit of normal, and a marked elevation above 5 times the upper limit is unusual and raises the possibility of an overlap syndrome. The serum bilirubin is normal in the early stages and rises slowly with progression, and serum immunoglobulins, especially IgM, are increased.
  • AMA positivity at a titre above 1:40. The most common technique for detecting AMA is indirect immunofluorescence (IIF); ELISA for the M2 subtype is more sensitive and specific, about 90% sensitive and 96% specific, and is recommended when IIF is negative. Other autoantibodies are often present: rheumatoid factor (RF) in about 70%, smooth-muscle antibody (SMA) in about 66%, ANA in about 50%, and anti-thyroid antibodies in about 41%.
  • Histological findings consistent with PBC. One of the earliest changes is loss of the canals of Hering, and the most common, and often the only, diagnostic clue is ductopenia, loss of bile ducts in more than 50% of the portal tracts.

The histological changes can be graded with the Ludwig staging system, which has four stages:

  1. stage 1 — focal lesions only around the bile ducts of the portal tract, known as florid duct lesions
  2. stage 2 — expansion of the lesion from the portal tract into the parenchyma, that is, interface hepatitis
  3. stage 3 — fibrosis and scarring
  4. stage 4 — a cirrhotic liver biopsy with fibrous septa and regenerative nodules

Liver biopsy is not generally required, because most patients are confirmed by serology and biochemistry and 2 of the 3 criteria are enough. When the serological and biochemical evidence is not sufficient, a liver biopsy is performed.