Explanation

Autoimmune hepatitis antibodies: what is measured?

This is not a single test but a blot: one strip holds several liver antigens side by side, including LKM-1 (a liver microsome), SLA/LP (soluble liver antigen), LC-1 (liver-specific cytosol) and AMA-M2 (mitochondria). The laboratory looks at which of these proteins your blood contains antibodies against. These antibodies are autoantibodies: immune proteins that the body mistakenly makes against its own tissue. Which band lights up helps distinguish which autoimmune disease of the liver is involved.

What can it detect?

Support when autoimmune hepatitis is suspected, a chronic liver inflammation caused by the body's own immune system
Distinction between autoimmune hepatitis type 1 and type 2 and primary biliary cholangitis
Addition to ANA and antibodies against smooth muscle when investigating an unexplained liver inflammation

Result

What does the result mean?

Positive result

A positive result means that antibodies against one or more of the liver antigens on the blot were found. On its own, that is not a diagnosis. Autoimmune hepatitis always requires more: abnormal liver values, a raised IgG, ruling out viral hepatitis and usually a liver biopsy. Which band is positive gives a direction: anti-LKM-1 and anti-LC-1 go with autoimmune hepatitis type 2, which mainly occurs in children and young people; anti-SLA/LP is rare but very specific for autoimmune hepatitis; AMA-M2 points more toward primary biliary cholangitis. With normal liver values, a positive result says little.

Negative result

A negative result means that none of these antibodies were found. This does not rule out autoimmune hepatitis: the most common form, type 1, is recognized precisely by antinuclear antibodies (ANA) and antibodies against smooth muscle, and these are not all on this blot. With abnormal liver values without these antibodies, the doctor looks further for other causes, such as a viral infection, alcohol, medicines or fatty liver disease.

After an abnormal result

With a positive result, the GP usually has the liver values measured or repeated and rules out viral hepatitis. If the liver values are abnormal, referral to a gastroenterologist follows for tests including IgG measurement, an ultrasound of the liver and often a liver biopsy; that biopsy is needed to diagnose autoimmune hepatitis. With normal liver values, no treatment is started.

Reliability

How reliable is the test?

The result is mainly meaningful in a liver inflammation whose cause is still unclear after standard testing. In people without symptoms and with normal liver values, the chance of autoimmune hepatitis is very small, and a positive result is then far more often a false positive than a true one. According to the Dutch Society for Clinical Chemistry (NVKC), a positive result also does not prove the disease: only together with an established liver inflammation is it a strong indication. Diagnosing autoimmune hepatitis also requires liver values, IgG and usually a liver biopsy.

What can affect the result?

The blot misses the antibodies that go with the most common form if ANA and antibodies against smooth muscle are not measured separately.
According to the Dutch Society for Clinical Chemistry (NVKC), antibodies against smooth muscle occur in fewer than 3 in 100 healthy people, usually temporarily; other bands can also light up without disease.
A blot says nothing about how active the liver inflammation is; that requires liver values, IgG and often a biopsy.
Laboratories use different blots with different antigens; which bands were tested is stated on the result report.

Who it is for

Who is the test useful for?

Useful for

Useful with a confirmed liver inflammation whose cause is unclear: long-standing raised liver values (ALAT and ASAT) without an explanation, especially if viral hepatitis, alcohol and medicines have already been ruled out. In people without symptoms and with normal liver values, the test adds nothing and the chance of a result that fits nothing is greater than the chance of a disease.

How common is it?

Autoimmune hepatitis is rare and more common in women than in men. The disease can start at any age; type 2 is seen mainly in children and young people. Because the disease is rare, positive results in people without liver symptoms occur relatively often without anything being wrong.

NVKC and Thuisarts.nl; no Dutch incidence figure has been verified

Drawbacks and risks

A positive result without abnormal liver values does occur and can lead to unnecessary worry and to further hospital testing, including a liver biopsy, that was not needed without symptoms.
A negative result does not rule out autoimmune hepatitis, because the most common form produces other antibodies; this can give false reassurance.

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