Diagnostic Workup for Autoimmune Hepatitis in a 49-Year-Old Woman
Order comprehensive autoantibody testing (ANA, SMA, anti-LKM, anti-SLA/LP), serum IgG levels, complete viral hepatitis screening, and proceed with liver biopsy—these are the essential diagnostic tests for autoimmune hepatitis. 1, 2
Core Laboratory Tests
Autoantibody Panel (Mandatory)
The 2025 EASL guidelines establish specific autoantibody thresholds for diagnosis 1:
- Anti-nuclear antibodies (ANA) and smooth muscle antibodies (SMA): Titers >1:40 (1 point) or >1:80 (2 points) when assessed on tissue sections
- For HEp-2 cells: >1:80 or 1:160 for 1 point; >1:160 or 1:320 for 2 points
- Anti-liver kidney microsomal antibodies (anti-LKM): Titer >1:40 (2 points)
- Anti-SLA/LP antibodies: Positive result (2 points)
Critical caveat: If ELISA-based testing is negative despite clinical suspicion, immunofluorescence testing (IFT) on tissue sections must be performed additionally 1. This is a common pitfall—relying solely on ELISA can miss cases.
Immunoglobulin G Level
- Measure serum IgG: >ULN (1 point) or >1.1× ULN (2 points) 1
- Important limitation: Only 25-39% of patients with acute presentation have elevated IgG 1, so normal IgG does not exclude AIH
- Patients with normal IgG at diagnosis may actually have better long-term outcomes and higher remission rates after treatment withdrawal 1
Aminotransferases and Liver Enzymes
- AST and ALT: Typically markedly elevated (often >5× ULN), though may be normal in cirrhotic patients 1
- Alkaline phosphatase (ALP) and GGT: Should be <2× ULN and <5× ULN respectively 1
- Significant elevations warrant exclusion of cholestatic variant forms or overlap syndromes
- GGT elevation with normal ALP is common in male patients and doesn't indicate cholangiopathy 1
Mandatory Exclusion Testing
The British Society of Gastroenterology 2025 guidelines mandate thorough screening 2:
Viral Hepatitis Panel (All Cases)
- Hepatitis B surface antigen (HBsAg) and anti-HBc
- Hepatitis C antibody and HCV RNA
- HIV testing
Additional Viral Testing (Acute/Icteric Presentations)
- Hepatitis A IgM
- Hepatitis E IgM
- CMV IgM
- EBV serology
Clinical pearl: Confirmed chronic HBV/HCV patients can have autoimmune features, creating diagnostic confusion 2. LKM-positive AIH has been associated with HCV infection 2. When uncertain, assess response to antiviral therapy before starting immunosuppression.
Liver Biopsy (Essential)
Liver biopsy should be performed routinely, ideally before starting immunosuppression, unless risks outweigh benefits 2. This is non-negotiable for diagnosis.
Histological Features to Assess
- Interface hepatitis with lymphoplasmacytic infiltration
- Plasma cell enrichment (highly suggestive)
- Lobular activity and confluent necrosis
- Fibrosis stage using Ishak scoring system 2
The 2022 International AIH Pathology Group criteria should be applied: "likely" corresponds to typical findings (2 points), "possible" to compatible findings (1 point) 1.
Prognostic importance: Bridging or multilobular necrosis indicates need for treatment; severe necrosis is a prognostic marker in acute-severe AIH 2.
Imaging Studies
Abdominal Ultrasound (Required)
- Exclude biliary obstruction 2
- Assess for cirrhotic morphology, splenomegaly, portal hypertension
Additional Imaging (As Needed)
- MRCP: If ALP/GGT significantly elevated to exclude overlap syndromes 2
- MRI has limited diagnostic role but can show surface nodularity (85%), reticular fibrosis pattern (80%), and hepatomegaly 3, 4
Diagnostic Scoring
Apply the Simplified AIH Criteria 1:
- Probable AIH: Score ≥6
- Definite AIH: Score ≥7
Maximum 2 points for autoantibodies; scoring includes autoantibodies + IgG + histology + viral exclusion.
Common Diagnostic Pitfalls
Seronegative AIH: Up to 5% of cases may be autoantibody-negative 5, 6. Don't exclude AIH based solely on negative autoantibodies—liver biopsy becomes even more critical.
Drug-induced autoimmune-like hepatitis (DIAILH): Can mimic AIH with identical features 2. Portal plasma cell-rich inflammation and absence of cholestasis favor AIH; eosinophils are not diagnostically useful 2.
MASLD confusion: MASLD typically has transaminases <150 U/L and more indolent presentation 2. Biopsy distinguishes these entities.
Overlap syndromes: Significant ALP/GGT elevation suggests AIH-PBC or AIH-PSC overlap 1, 7. Perform MRCP and consider antimitochondrial antibodies.
The diagnostic algorithm prioritizes excluding viral hepatitis and biliary obstruction first, then establishing positive autoimmune serology and histological confirmation, while calculating the simplified diagnostic score to reach probable or definite AIH diagnosis.