What are the diagnostic criteria for autoimmune hepatitis (AIH)?

From the Guidelines

Confirming autoimmune hepatitis requires a comprehensive diagnostic approach involving blood tests, imaging, and liver biopsy, with the most recent guidelines recommending the use of a revised diagnostic scoring system or a simplified diagnostic scoring system 1. To diagnose autoimmune hepatitis (AIH), the following steps should be taken:

• Initial testing includes liver function tests to detect elevated liver enzymes (ALT, AST), along with specific autoantibody tests such as antinuclear antibodies (ANA), anti-smooth muscle antibodies (ASMA), and anti-liver kidney microsomal antibodies (anti-LKM) 1.
• Elevated immunoglobulin G (IgG) levels are also characteristic of AIH, although normal or mildly elevated IgG levels do not rule out the diagnosis 1.
• Imaging studies like ultrasound or CT scans help rule out other liver conditions, such as viral hepatitis, drug-induced liver injury, Wilson's disease, and alcoholic liver disease.
• The definitive diagnosis typically requires a liver biopsy, which shows characteristic features including interface hepatitis, lymphoplasmacytic infiltration, and fibrosis 1.
• A scoring system that combines clinical, laboratory, and histological findings can be used to diagnose AIH, with a score of 6 or more indicating probable or definite AIH 1.
• Other conditions that must be excluded include viral hepatitis, drug-induced liver injury, Wilson's disease, and alcoholic liver disease.
• Early diagnosis is crucial as prompt treatment with immunosuppressive medications can prevent progression to cirrhosis and liver failure 1. Some key points to consider in the diagnosis of AIH include:
• The presence of autoantibodies, such as ANA, ASMA, and anti-LKM, which are characteristic of AIH 1.
• The elevation of serum IgG levels, which is a common feature of AIH, although normal or mildly elevated IgG levels do not rule out the diagnosis 1.
• The importance of liver biopsy in confirming the diagnosis of AIH, as it shows characteristic features including interface hepatitis, lymphoplasmacytic infiltration, and fibrosis 1.
• The use of a scoring system to diagnose AIH, which combines clinical, laboratory, and histological findings 1.

From the Research

Diagnostic Criteria for Autoimmune Hepatitis

To confirm autoimmune hepatitis, the following criteria can be used:

• Clinical presentation: jaundice, fatigue, pruritus, and abdominal pain 2
• Biochemical analysis: elevated alanine transaminase, aspartate transaminase, and total bilirubin 2
• Autoantibody profile:
  • Type 1: anti-nuclear (ANA) and/or anti-smooth muscle (SMA) antibodies 3, 4
  • Type 2: anti-liver kidney microsomal type 1 (anti-LKM-1) antibodies 3
• Histological examination: interface hepatitis with lymphoplasmacellular infiltrates on liver biopsy 3, 5
• Diagnostic scoring systems:
  • Revised and simplified diagnostic scores established by the International Autoimmune Hepatitis Group (IAIHG) 4, 6
  • Nonstandard autoantibodies, including antibodies to actin, α-actinin, soluble liver antigen, perinuclear antineutrophil antigen, asialoglycoprotein receptor, and liver cytosol type 1 5

Laboratory Tests

Laboratory tests that can support the diagnosis of autoimmune hepatitis include:

• Autoantibody detection: ANA, SMA, anti-LKM-1 3, 4, 2
• Immunoglobulin G (IgG) levels: elevated in 86% of patients with acute onset AIH 2
• Liver function tests: alanine transaminase, aspartate transaminase, total bilirubin 2

Differential Diagnosis

A thorough differential diagnosis is necessary to exclude other diseases that may resemble autoimmune hepatitis, such as:

• Viral hepatitis
• Drug-induced liver injury
• Primary biliary cirrhosis
• Primary sclerosing cholangitis 4, 5