From the Guidelines
Non-alcoholic steatohepatitis (NASH) should be diagnosed through a combination of clinical evaluation, laboratory tests, imaging studies, and sometimes liver biopsy, with a focus on non-invasive methods such as transient elastography (FibroScan) and multiparametric MRI indices, as recommended by the most recent study 1. The initial assessment typically includes blood tests to check liver enzymes (ALT, AST), which are often elevated in NASH, along with tests to rule out other liver diseases such as viral hepatitis, autoimmune hepatitis, and hemochromatosis. Imaging studies like ultrasound, CT scan, or MRI can detect fatty liver but cannot definitively diagnose NASH.
Key Diagnostic Considerations
- The gold standard for diagnosing NASH is a liver biopsy, which can show the characteristic features of steatosis (fat accumulation), inflammation, and hepatocyte ballooning, as noted in 1.
- Non-invasive methods are increasingly being used, including specialized blood test panels like FibroTest or imaging techniques like transient elastography (FibroScan), which can assess liver stiffness as a marker of fibrosis.
- Risk factors such as obesity, type 2 diabetes, dyslipidemia, and metabolic syndrome should be evaluated as they are commonly associated with NASH, as highlighted in 1.
- The diagnosis requires excluding significant alcohol consumption (typically defined as >21 drinks per week for men and >14 drinks per week for women) to differentiate NASH from alcoholic steatohepatitis.
Recent Advances in Diagnosis
- A prediction model based on liver stiffness, CAP (assessed using transient elastography), and ALT levels has been proposed as a non-invasive surrogate to diagnose NASH, as reported in 1.
- Multiparametric MRI indices, which score the results from various MRI techniques, have been shown to differentiate NASH from NAFL with sensitivity of 80%, specificity of 85.2%, and an AUC of 0.883, as demonstrated in 1.
From the Research
Diagnosis of Nash
To diagnose Nash, the following methods can be used:
- Imaging tests such as ultrasound, CT scan, and MRI to assess liver fat and fibrosis [ 2, 3,4 ]
- Liver biopsy to assess liver inflammation and scarring [ 2, 3 ]
- Blood tests such as AST/ALT ratio, NAFLD fibrosis score, and NAFLD liver fat score to assess liver function and fibrosis [ 2 ]
- Transient elastography to assess liver stiffness and fibrosis [ 2, 3 ]
- MRI proton density fat fraction (MRI-PDFF) to quantify liver fat content 3, 5
Diagnostic Challenges
- Liver biopsy is invasive and subject to sampling and interobserver variability 3, 5
- Imaging biomarkers for NASH diagnosis have modest diagnostic accuracy when used alone 3
- There is a need for non-invasive, objective, and quantitative biomarkers for NASH diagnosis and treatment response 3, 5