How Do You Test For Autoimmune Hepatitis?
Autoimmune hepatitis, as the name implies, is the inflammation of liver due to attack by its own immune system. It is a chronic disease that is related to other autoimmune diseases. The other autoimmune diseases include inflammatory bowel disease, ulcerative colitis, rheumatoid arthritis, Grave’s disease, scleroderma, lupus, Sjogren’s disease, thyroiditis and type 1 diabetes. Autoimmune hepatitis may have a genetic predisposition and may run in families. Although, some patients may present with acute symptoms such as arthralgia (joint pain), about 45% are asymptomatic and identification is done only after abnormal liver panel.
How Do You Test For Autoimmune Hepatitis?
Autoimmune hepatitis should be diagnosed as early as possible and if a patient has acute liver failure or acute hepatitis then autoimmune hepatitis should be considered for differential diagnosis. In addition to diagnosing it early in life, it is also imperative to differentiate autoimmune hepatitis from primary biliary cirrhosis and in children with autoimmune hepatitis; its progression should be monitored with regular testing. Other forms of hepatitis such as toxic, hereditary or infectious forms should be ruled out.
The testing of autoimmune hepatitis includes liver function tests, which are usually found abnormal with elevated levels of ALT and/or AST. They are generally <500 U/L, but on occasions can be higher and range from 500-1000 U/L. The elevated levels of aminotransferases do not correlate well with the degree of hepatic necrosis, but if the values are elevated around 1000 U/L then it may indicate acute hepatitis or a severe flare up of pre-existing disease. If the values of aminotrasferases remain elevated even after therapy, then this might indicate persistence of liver inflammation. In patients with autoimmune disease, serum bilirubin, alkaline phosphatase levels are mild to moderately be elevated in about 90% of the patients. Hypoalbuminemia and prothrombin time prolongation is seen in active disease.
Tests are also carried out for the presence of globulin, gamma globulins and immunoglobulins such as IgG. Gamma globulin values range from 3-4 g/dl and can even be elevated to 5-6 g/dl and IgG are nearly 1.5 times elevated from upper normal range. Monitoring of gamma globulin or IgG is vital to test therapy response.
Autoantibody testing is also carried out for autoimmune hepatitis, which include smooth muscle antibody (actin antibody), antinuclear antibodies (ANA) and liver/kidney microsome antibody (LKM-1). Type1 autoimmune hepatitis mostly shows the presence of smooth muscle antibodies as well as antinuclear antibodies, which is typically a disease of the adults. Type 2 autoimmune hepatitis is seen in children and shows the presence of liver/kidney microsome antibodies.
Complete blood test is also carried out, which may show mild leucopenia, anemia, thrombocytopenia, elevated ESR and in some patients even show eosinophilia.
Hepatic imaging tests such as abdominal ultrasound or CT imaging can be done that may show presence of active inflammation or necrosis. They are not a definitive diagnostic tool for autoimmune hepatitis, but they can be performed to rule out hepatocellular carcinoma.
Liver biopsy is a vital diagnostic tool for autoimmune hepatitis. It can be performed either percutaneously or by transjugular route. Transjugular route is preferred in cases of difficulty accessing the liver, ascites and/or severe thrombocytopenia or other bleeding disorders.
The histologic findings on the specimens of liver biopsy help determine diagnosis of autoimmune disease as well as its severity. It helps differentiate autoimmune disease from other chronic hepatitis infection, alcohol-induced hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis and drug-induced liver disease. Autoimmune hepatitis is characteristic of portal mononuclear cell infiltrate and on occasions plasma cell infiltrate along with interface hepatitis (piecemeal necrosis), bridging necrosis and fibrosis.
The presence of interface hepatitis does not indicate the progression of disease; however, the presence or absence of cirrhosis on liver biopsy is an important factor in the determination of prognosis of a patient. All the above tests including histopathologic findings, antibody testing, immunoglobulin presence and other tests should correlate with each other to reach a definitive diagnosis for autoimmune disease.
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