What is the diagnostic workup for metabolic associated steatohepatitis (MASH)?

Diagnostic Workup for Metabolic-Associated Steatohepatitis (MASH)

The diagnostic workup for MASH requires a sequential approach starting with exclusion of other liver diseases, followed by confirmation of hepatic steatosis with cardiometabolic risk factors, and then fibrosis staging using noninvasive tests—with liver biopsy reserved for cases with discordant results or when definitive diagnosis is needed. 1

Step 1: Exclude Other Causes of Liver Disease

Before diagnosing MASH, you must rule out competing etiologies that can mimic or coexist with metabolic liver disease 1:

• Alcohol consumption assessment: Quantify intake to distinguish MASLD (≤20 g/day females, ≤30 g/day males) from MetALD (20-50 g/day females, 30-60 g/day males) or alcohol-associated liver disease (>50 g/day females, >60 g/day males). Use validated questionnaires (AUDIT-C) and consider phosphatidylethanol biomarkers if underreporting is suspected 1, 2

• Viral hepatitis screening: Test for hepatitis B and C 1

• Autoimmune liver disease: Check anti-nuclear antibody (ANA) and anti-smooth muscle antibody (ASMA). If high-titer positive, pursue quantitative immunoglobulins and consider liver biopsy 1

• Iron overload: Assess iron studies to exclude hemochromatosis 1

• Medication-induced steatosis: Review for corticosteroids, tamoxifen, methotrexate 3

Step 2: Confirm Hepatic Steatosis and Cardiometabolic Risk Factors

Steatosis detection using one of the following 1:

• FibroScan CAP ≥280 dB/m (preferred initial test)
• MRI-proton density fat fraction ≥5% (quantitative alternative)
• Ultrasound, CT, or MRI (qualitative assessment)

Cardiometabolic criteria (at least one required) 1, 2:

• Overweight/obesity (BMI ≥25 kg/m² or waist circumference elevated)
• Type 2 diabetes or prediabetes/impaired glucose metabolism
• Hypertension
• Hypertriglyceridemia
• Low HDL-cholesterol

Liver enzyme elevation suggestive of MASH 1:

• AST >17 IU/L (females) or >20 IU/L (males)

Step 3: Fibrosis Staging with Noninvasive Tests

A two-step sequential approach is recommended to identify clinically significant fibrosis (F2-F3), which defines "at-risk MASH" associated with liver-related morbidity and mortality 1:

Initial Screening: FIB-4 Index

• FIB-4 <1.3 (age ≤65 years) or **<2.0** (age >65 years): Low risk, reassess every 1-3 years 1
• FIB-4 ≥1.3 (age ≤65 years) or ≥2.0 (age >65 years): Proceed to second-tier testing 1
• FIB-4 >2.67: High risk, refer to hepatology 1

Second-Tier Testing: Liver Stiffness Measurement

Vibration-Controlled Transient Elastography (VCTE/FibroScan) 1:

• <8.0 kPa: Rules out advanced fibrosis, intensify cardiometabolic management 1
• 10-15 kPa: Suggests F2-F3 fibrosis (significant/advanced fibrosis) 1
• 15.1-20 kPa: Advanced fibrosis (F3) in absence of cirrhosis features 1
• >20 kPa: Suggests cirrhosis, requires portal hypertension assessment 1

Technical requirements for VCTE: Obtain ≥10 measurements with interquartile range <30%, patient fasted ≥3 hours, ensure absence of rib echo on images 1

Alternative liver stiffness methods 1:

• Magnetic Resonance Elastography (MRE): 3.0-4.3 kPa suggests F2-F3 1
• Shear Wave Elastography (SWE): Use adapted thresholds 1

Enhanced Liver Fibrosis (ELF) score (when elastography unavailable) 1:

• ELF 9.2-9.7: Requires corroboration with additional noninvasive test 1
• ELF 9.8-10.4: May identify F2-F3 fibrosis 1
• ELF 10.5-11.3: Exercise caution to exclude cirrhosis 1

Step 4: Liver Biopsy (Selective Use)

Liver biopsy is NOT required for clinical management but remains the gold standard for definitive MASH diagnosis 1. Consider biopsy in these scenarios 1:

• Discordant noninvasive test results between different modalities
• Suspected autoimmune liver disease requiring histologic confirmation
• Clinical trial enrollment or when histologic confirmation impacts treatment decisions
• Historical biopsy interpretation: If biopsy within 12 months shows MASH with F2-F3, treatment may proceed regardless of current noninvasive test values (unless portal hypertension present) 1

MASH histologic criteria: Presence of steatosis, lobular inflammation, and hepatocellular ballooning with NAFLD Activity Score (NAS) ≥4 4

Critical Pitfalls to Avoid

• Do not rely solely on patient self-report for alcohol consumption—use validated questionnaires and biomarkers when suspicion exists 2
• Do not miss autoimmune hepatitis—several MASH trials inadvertently included these cases, leading to elevated liver enzymes during treatment 1
• Do not use single noninvasive tests in isolation—sequential testing with multiple modalities increases diagnostic precision 1
• Do not overlook technical quality of VCTE—poor technique yields unreliable results 1
• Do not diagnose MASH without confirming at least one cardiometabolic risk factor—this distinguishes MASLD from other steatotic liver diseases 1, 2