What lab work should be done for a patient with suspected autoimmune liver disease?

Laboratory Workup for Autoimmune Liver Disease

For suspected autoimmune liver disease, obtain a standard liver aetiology screen including: hepatitis B surface antigen, hepatitis C antibody with reflex PCR, anti-mitochondrial antibody, anti-smooth muscle antibody, antinuclear antibody, serum immunoglobulins, and simultaneous serum ferritin with transferrin saturation, alongside abdominal ultrasound. 1

Initial Liver Blood Tests

• Bilirubin, albumin, alanine aminotransferase (ALT), alkaline phosphatase (ALP), and γ-glutamyltransferase (GGT) should be obtained as the initial investigation for potential liver disease, together with a full blood count if not performed within the previous 12 months 1

• AST should be measured in addition to ALT to calculate the AST:ALT ratio, which helps differentiate patterns of liver injury 1

• Prothrombin time/INR is important to fully define synthetic liver function, particularly in patients with symptoms or signs of cirrhosis 1

Standard Autoimmune Liver Disease Serology Panel

Essential Autoantibodies

• Antinuclear antibody (ANA) at titers ≥1:40 in adults (≥1:20 in children) is a key marker for autoimmune hepatitis type 1 1

• Anti-smooth muscle antibody (SMA) at titers ≥1:40 in adults (≥1:20 in children) is associated with autoimmune hepatitis type 1, with VGT pattern on immunofluorescence being most specific 1

• Anti-liver/kidney microsomal antibody type 1 (anti-LKM-1) at titers ≥1:40 in adults (≥1:10 in children) defines autoimmune hepatitis type 2 1

• Anti-mitochondrial antibody (AMA) is the hallmark of primary biliary cholangitis, targeting the E2 subunits of pyruvate dehydrogenase complex 1

Supplemental Autoantibodies When Conventional Tests Are Negative

• Anti-soluble liver antigen/liver pancreas (anti-SLA/LP) should be tested in patients with suspected autoimmune hepatitis who are negative for conventional autoantibodies 1

• Anti-liver cytosol type 1 (anti-LC1) is another marker for autoimmune hepatitis type 2 1

• Atypical perinuclear anti-neutrophil cytoplasmic antibodies (pANCA) may suggest primary sclerosing cholangitis or autoimmune hepatitis 1

• Anti-actin antibodies provide additional diagnostic support when conventional markers are equivocal 1

Immunoglobulin Assessment

• Serum immunoglobulin G (IgG) levels should be measured, as hypergammaglobulinemia (IgG >1.5 times normal) supports the diagnosis of autoimmune hepatitis 1

• Quantitative immunoglobulins (IgG, IgM, IgA) help differentiate between autoimmune liver diseases, with elevated IgM suggesting primary biliary cholangitis 1

• IgG >2× ULN combined with anti-smooth muscle antibody titer >1:80 is characteristic of autoimmune hepatitis/primary biliary cholangitis overlap syndrome 1

Viral Hepatitis Exclusion

• Hepatitis B surface antigen (HBsAg) must be tested to exclude hepatitis B virus infection 1

• Hepatitis C antibody with reflex PCR if positive is essential to rule out hepatitis C as the cause of liver inflammation 1

• Hepatitis A IgM, hepatitis E antibodies (IgG and IgM), and hepatitis D antibodies (in HBsAg-positive patients) should be considered based on clinical presentation 1

Iron Studies

• Simultaneous serum ferritin and transferrin saturation are required to exclude hereditary hemochromatosis as a cause of liver disease 1

• These tests should be interpreted together, as ferritin alone can be elevated in inflammatory conditions 1

Additional Metabolic and Genetic Testing

• Alpha-1-antitrypsin level should be included in children and considered in adults with unexplained liver disease 1

• Ceruloplasmin (in patients >3 years old) should be measured to exclude Wilson's disease, particularly in younger patients 1

• Slit lamp examination for Kayser-Fleischer rings and genetic testing may be needed if Wilson's disease is suspected 1

Imaging Studies

• Abdominal ultrasound is part of the standard liver aetiology screen to evaluate liver parenchyma, biliary tree, and exclude focal lesions 1

• MRCP should be performed if cholestatic pattern exists without obvious obstruction on ultrasound, particularly to evaluate for primary sclerosing cholangitis 1

Timing and Interpretation Considerations

• Abnormal liver blood test results should only be interpreted after review of previous results, past medical history, and current medical condition 1

• The extent of liver blood test abnormality is not necessarily a guide to clinical significance; this is determined by the specific analyte that is abnormal and the clinical context 1

• For autoimmune hepatitis specifically, 75% of patients have non-specific symptoms such as fatigue, nausea, or anorexia, making laboratory testing essential for diagnosis 1

Critical Pitfalls to Avoid

• Do not assume a single positive autoantibody confirms autoimmune liver disease; diagnosis requires compatible clinical signs, laboratory abnormalities, serological findings, and histological evidence with exclusion of other causes 1

• Anti-LKM-1 and AMA both stain renal tubules on immunofluorescence and are frequently confused; careful interpretation by experienced personnel is essential 1

• Low-titer autoantibodies (1:40) in adults can occur in healthy individuals and other conditions; clinical context and additional testing are crucial 1

• In children, any level of autoantibody reactivity is clinically relevant, so positivity at dilutions of 1:20 for ANA and SMA and even 1:10 for anti-LKM-1 should be considered significant 1

• Autoantibodies can be present in drug-induced liver injury and drug-induced autoimmune hepatitis, making it difficult to distinguish from idiopathic autoimmune hepatitis without liver biopsy 1