MRI-PDFF: Liver Fat
MRI-PDFF (proton density fat fraction) measures how much fat is in the liver. It is the most accurate noninvasive method for measuring liver fat, with high agreement with biopsy findings.
AI Summary The MAST score combines an MRI-PDFF liver fat measurement, an MRE liver stiffness measurement, and an AST blood test into one number. It estimates the chance of significant fibrosis or MASH without a biopsy. Below 0.165 is low risk, 0.165 to 0.242 is intermediate, and above 0.242 is high. The score is an estimate, not a diagnosis, so your doctor reads it with your other results and may suggest follow-up or a specialist visit.
Source: www.liverdirectory.com
MAST Score
Medically Reviewed.
The MAST score, short for MRI-AST, is a non-invasive score for people with fatty liver disease. It combines two MRI measurements with one blood test result to estimate how likely you are to have significant liver scarring (fibrosis) or metabolic dysfunction–associated steatohepatitis (MASH).
It does not need a needle in your liver. Your care team reads the score alongside your health history and other tests, and uses it to decide whether you need closer monitoring or a visit with a liver specialist.
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NONINVASIVE FATTY LIVER SCORE
What Is the MAST Score?
The MAST score (MRI-AST score) estimates two things in a person with fatty liver disease: how much fibrosis (scar tissue) the liver has, and how likely it is that the liver has MASH. MASH, formerly called NASH, is a more severe form of fatty liver. If it goes untreated, it can lead to fibrosis, cirrhosis, or liver failure.
The MAST score is not a single scan. It is a calculation. It uses an MRI to measure liver fat and liver stiffness, and a blood test for a liver enzyme called AST. The three results combine into one number.
The score gives your doctor a detailed look at liver health without a biopsy. A liver biopsy removes a small piece of liver tissue. The MAST score does not.
The MAST score is one of several MAFLD / MASH scores. Each uses different inputs to estimate the same kind of risk.
MAST Score at a Glance
- MAST stands for MRI-AST. It combines MRI-PDFF (liver fat), MRE (liver stiffness), and an AST blood test.
- The result is one number that estimates the likelihood of significant fibrosis or MASH.
- A score below 0.165 is low risk. A score from 0.165 to 0.242 is intermediate risk. A score above 0.242 is high risk.
- MRI-PDFF is the most accurate noninvasive method for measuring liver fat.
- The MRI uses no radiation, and the score does not require a liver biopsy.
- The score is an estimate, not a diagnosis. Your doctor reads it with your other results.
MRI AND BLOOD TEST INPUTS
What Goes into the MAST Score
The score takes three results and turns them into one number. Two come from the same MRI visit. One comes from a blood draw.
MRE: Liver Stiffness
MRE (magnetic resonance elastography) measures liver stiffness. Scar tissue makes the liver firmer, so stiffness is a stand-in for fibrosis. MRE creates a visual map of stiffness across the liver.
AST: A Blood Marker of Liver Injury
AST (aspartate aminotransferase) is a liver enzyme that rises with liver injury. It comes from a standard blood draw, often part of routine liver blood work.
WHEN DOCTORS ORDER IT
Why Your Doctor May Order a MAST Score
Doctors use the MAST score when they need a closer look at fatty liver disease and want to avoid a biopsy.
You Have Risk Factors for Fatty Liver Disease
Obesity, diabetes, and high cholesterol raise the risk of fatty liver disease. If you have these, your doctor may use the score to check for scarring or early MASH.
Your Doctor Wants to Assess Scarring or Early MASH
The score estimates the chance of significant fibrosis or MASH. Finding either early gives you time to act before scarring advances.
You Are Being Monitored Over Time
A repeat score can show whether your liver is changing after lifestyle or medical changes.
You Want an Option Other than a Biopsy
A biopsy carries risks, including pain and bleeding, and the sample can miss the problem area. Noninvasive tests are safer and repeatable. Sequential testing, such as a blood test followed by imaging, also helps reduce unnecessary biopsies.
MRI AND BLOOD DRAW VISIT
What Happens When You Get a MAST Score
There is no separate MAST test. You have an MRI visit and a blood draw, and your care team calculates the score from the results.
Steps in Getting a MAST Score
- Your doctor orders an MRI that measures liver fat (MRI-PDFF) and liver stiffness (MRE), plus an AST blood test.
- At the imaging visit, you lie on a table that slides into a tunnel-shaped MRI scanner. You need to stay very still while the scanner records images.
- MRI uses powerful magnets and radio waves, not radiation. In some MRI exams, a contrast dye is injected. Ask your care team whether yours needs it.
- A provider draws blood for the AST test, usually from a vein in your arm.
- Your care team combines the three results into your MAST score and reviews it with you.
Your clinic will tell you how to prepare, including whether to fast before the scan. Tell the imaging team about any allergies, metal implants, or discomfort in small spaces before the exam.
LOW, MID, AND HIGH RISK
MAST Score Ranges and What They Mean
Your score falls into one of three risk groups. The groups show how likely it is that you have significant fibrosis or MASH. They are not a diagnosis.
MAST Score
Combines MRI-PDFF, MRE, and AST into one risk estimate.
0.165 to 0.242 (intermediate risk)
Below 0.165 is low risk. Little or no fibrosis or MASH is likely. Your doctor may advise a healthy lifestyle and routine monitoring.
0.165 to 0.242 is intermediate risk. Some fibrosis or fat buildup may be present. Your doctor may advise more monitoring, more imaging, or lifestyle changes.
Above 0.242 is high risk. Significant fibrosis or MASH is likely. Your doctor will likely advise a specialist evaluation and may discuss treatment.
A Score Is One Piece of the Picture
A high score does not confirm MASH, and a low score does not rule out every problem. A biopsy may still be used when noninvasive results are unclear or before some treatments.
ACCURACY AND TEST LIMITATIONS
What the MAST Score Cannot Tell You
It Estimates Risk. It Does Not Diagnose.
Histology, the study of a liver tissue sample, remains the gold standard for diagnosing MASH. The MAST score helps your doctor decide who needs that step.
Its Accuracy Differs by Stage
Noninvasive tests are more accurate for finding cirrhosis than for telling apart the middle stages of fibrosis. An intermediate score is therefore a reason for follow-up, not a firm answer.
AST Can Rise for Other Reasons
AST rises with liver injury. Other liver problems can raise it too, so your doctor considers your full history when reading the score.
FIBROSIS AND MASH TEST OPTIONS
MAST Score Compared with Other Tests
Several non-invasive options estimate the same kind of risk. Your care team chooses based on your situation and what testing is available.
| Test | What it uses | What it estimates |
|---|---|---|
| MAST score | MRI-PDFF, MRE, and AST blood test | Likelihood of significant fibrosis or MASH |
| FAST score | FibroScan stiffness, FibroScan fat measure (CAP), and AST | Likelihood of MASH with significant fibrosis |
| cTAG score | MRI marker cT1, AST, and blood glucose | Risk of significant fibrosis |
| Liver biopsy | A small sample of liver tissue | Fibrosis and MASH, confirmed under a microscope |
Learn more about the [FAST score](/liver-tests/medical-scores/mafld-mash-scores/fast-score) and the [SAFE score](/liver-tests/medical-scores/mafld-mash-scores/safe-score).
FOLLOW-UP AFTER YOUR SCORE
What to Do After Your Result
Review the Result with Your Care Team
Ask your doctor to explain your score and which risk group you fall into. Ask what the result means for your follow-up schedule. Bring a list of your medicines and any earlier liver test results.
Act on the Parts You Can Change
Lifestyle change is the cornerstone of care for fatty liver disease. Helpful steps include regular physical activity, gradual weight loss of 5 to 10 percent if you are overweight, a diet rich in vegetables, fruits, whole grains, lean protein, and healthy fats, and limiting alcohol. Early fatty liver can often be reversed with these steps.
Ask About a Specialist Visit
A high score, or a score your doctor finds unclear, often leads to a visit with a liver specialist. Some adults with MASH and moderate to advanced fibrosis may be considered for medicine such as [resmetirom](/liver-therapies/metabolic-masld-mash-therapies/thr-beta-agonist-therapy/resmetirom). Your specialist decides what fits you. Learn more about [metabolic therapies](/liver-therapies/metabolic-masld-mash-therapies/additional-metabolic-therapies).
AFTER YOUR SCORE
Treatment Options
Learn what treatment can involve
Your score helps your doctor decide on next steps. Read about therapies for fatty liver disease and MASH.
Find a liver specialist near you
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Common Questions
Answers to Common MAST Score Questions
What is a MAST score?
A MAST score is a number that estimates how likely you are to have significant liver fibrosis or MASH. MAST stands for MRI-AST. It is a calculation, not a single scan. It combines liver fat (MRI-PDFF), liver stiffness (MRE), and an AST blood test. AST is a liver enzyme that rises with liver injury. The score is a risk estimate, not a diagnosis. Your doctor reads it with your health history and your other test results.
Does the MAST score need a liver biopsy?
No. The MAST score comes from an MRI and a blood test, so no tissue sample is taken. A liver biopsy removes a small piece of liver tissue. A biopsy carries risks, including pain and bleeding, and the sample can miss the problem area. Your doctor may still suggest a biopsy if your results are unclear or if you need confirmation before some treatments.
What does a high MAST score mean?
A score above 0.242 is high risk. It means significant fibrosis (scar tissue) or MASH is likely. It does not confirm a diagnosis. Histology, the study of a liver tissue sample, remains the gold standard for diagnosing MASH. Your doctor will likely advise a specialist evaluation and may discuss next steps, including treatment. Ask your doctor what the result means for your follow-up schedule.
What does a low MAST score mean?
A score below 0.165 is low risk. It points to little or no fibrosis or MASH. A low score does not rule out every problem, so your doctor still considers your full history. Your doctor may advise a healthy lifestyle and routine monitoring. Keep up with any follow-up visits, even when your result is reassuring.
What does an intermediate MAST score mean?
Scores from 0.165 to 0.242 are intermediate risk. Some fibrosis or fat buildup may be present. This range is a reason for follow-up, not a firm answer. Noninvasive tests are more accurate for finding cirrhosis than for telling apart the middle stages of fibrosis. Your doctor may suggest more monitoring, more imaging, or lifestyle changes.
Medical disclaimer: LiverDirectory provides educational information and a directory of providers. It does not provide medical advice, diagnosis, or treatment. Always consult a licensed physician regarding any medical condition.