Advanced Liver Disease
You have advanced liver disease, including cirrhosis or chronic hepatitis, and your care team wants an early read on your risk of hepatic encephalopathy.
AI Summary The HAST/HASA score estimates your risk of hepatic encephalopathy (HE) by combining blood tests — ammonia, bilirubin, INR, and creatinine — with a brief cognitive test. A score below 10 suggests minimal risk, 10 to 20 intermediate risk, and above 20 high risk that usually needs urgent evaluation. Doctors use it to monitor risk and treatment response. It is not a diagnosis; the West Haven Criteria grades severity. Triggers like infection or dehydration can raise your score.
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HAST / HASA Score
Medically Reviewed.
The HAST (Hepatic Assessment of Subclinical Toxins) / HASA (Hepatic Assessment of Subclinical Ammonia) score is a calculation that combines blood test results with a brief cognitive assessment to estimate your risk of hepatic encephalopathy (HE), a complication of liver disease that affects brain function.
Doctors use it to catch early, subtle changes in thinking before they become obvious, and to track how that risk changes over time as liver disease progresses or as treatment takes effect.
This page explains what goes into the score, how to read a low, moderate, or high result, how it relates to the West Haven Criteria for staging HE, and what typically happens next.
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Hepatic Encephalopathy Risk Basics
What Is the HAST/HASA Score?
The HAST/HASA score estimates your risk of hepatic encephalopathy (HE), a complication of liver disease that affects how your brain works. HE can cause confusion, personality changes, disrupted sleep, or trouble concentrating. It happens when a damaged liver can no longer clear certain toxins — most notably ammonia — from the blood.
The name stands for Hepatic Assessment of Subclinical Toxins (HAST) and Hepatic Assessment of Subclinical Ammonia (HASA). Unlike imaging or a liver biopsy, it involves no procedure. It combines routine blood test results with a short cognitive assessment, so your care team can calculate it safely and repeat it as often as needed.
HAST/HASA Score at a Glance
- The score combines blood results — ammonia, bilirubin, INR, and creatinine — with a brief cognitive test to estimate hepatic encephalopathy risk.
- A score below 10 suggests minimal risk, 10 to 20 suggests intermediate risk, and above 20 suggests high risk.
- It is non-invasive and repeatable, and it's typically used alongside — not instead of — clinical staging tools like the West Haven Criteria.
- Your doctor may recalculate it over time to see whether treatments such as lactulose or rifaximin are helping.
When Doctors Order It
Why You Might Need Your HAST/HASA Score
Your doctor may calculate your HAST/HASA score in several situations.
History of Cognitive Changes
You have a history of confusion, memory problems, or subtle changes in thinking that could signal hepatic encephalopathy.
Ongoing Monitoring
Your doctor wants to track your hepatic encephalopathy risk over time as your liver disease or overall health changes.
Treatment Response
You are evaluating how well a therapy — such as lactulose, rifaximin, or dietary changes — is affecting your brain function.
Score Formula and Inputs
What Goes Into the HAST/HASA Score
The HAST/HASA score combines several blood test results with a brief cognitive assessment. Your care team weighs each factor using a set formula to produce a single number.
Blood Ammonia Level
Elevated ammonia is linked to the cognitive changes seen in hepatic encephalopathy, so it carries the largest weight in the equation.
Liver Function Markers
Bilirubin and INR reflect how well the liver is clearing waste products and producing clotting factors — both affected as liver function declines.
Kidney Function
Creatinine reflects kidney function, because the kidneys help clear the same toxins the liver would otherwise remove.
Cognitive Test Score
A brief psychometric test, such as the Number Connection Test, the Stroop test, or the Mini-Mental State Exam, adds a direct measure of current thinking and attention.
Formula: HAST/HASA = (0.03 × blood ammonia) + (0.02 × bilirubin) + (0.04 × INR) + (0.01 × creatinine) + cognitive test score. Your care team may also factor in sodium, potassium, or glucose when relevant.
Low, Moderate, High Results
HAST/HASA Score Reference
Once your care team calculates your HAST/HASA score, they compare it against three risk bands. Always discuss what your specific result means with your doctor — the score is one part of a broader clinical picture.
- Low Score (Below 10)
- Minimal risk. Low likelihood of hepatic encephalopathy, with normal cognitive function. Routine monitoring is usually recommended.
- Moderate Score (10 to 20)
- Intermediate risk. Some cognitive changes or subtle hepatic encephalopathy may be present. Your doctor may recommend closer monitoring and possible interventions.
- High Score (Above 20)
- High risk. Worsening brain function and a significant risk of hepatic encephalopathy. This usually calls for urgent evaluation and treatment.
Always Read Your Score With Your Care Team
The HAST/HASA score is not a standalone diagnosis. It's meant to be read alongside your symptoms, medical history, and other tools such as the West Haven Criteria.
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HE Staging and Triggers
Clinical Context
How This Score Relates to West Haven Grading
The HAST/HASA score is a risk-estimation tool, not a diagnostic staging system. When your doctor confirms hepatic encephalopathy is present, they typically stage its severity using the [West Haven Criteria](/liver-tests/medical-scores/hepatic-encephalopathy-scores/west-haven-criteria), which grades mental status from minimal changes (covert HE) through confusion and coma (overt HE, grades I to IV). Your care team may use both tools together: the HAST/HASA score to flag rising risk, and West Haven grading to describe how severe an episode actually is.
Why Ammonia Alone Isn't Enough
Blood ammonia is a key input in the HAST/HASA equation, but it has an important limitation: an elevated ammonia level alone does not confirm hepatic encephalopathy, and a normal level does not fully rule it out once symptoms are present. That's why the score pairs ammonia with liver function markers, kidney function, and a direct cognitive test, rather than relying on ammonia by itself.
What Can Cause Your Score to Rise
Hepatic encephalopathy is often triggered by a specific event — an infection, gastrointestinal bleeding, constipation, dehydration, or a new sedating medication. If your HAST/HASA score rises, your care team will typically look for and treat one of these triggers alongside adjusting your HE therapy.
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Common Questions
Answers to Common HAST / HASA Score Questions
What does the HAST/HASA score measure?
The HAST/HASA score estimates your risk of hepatic encephalopathy (HE), a complication of liver disease that affects how your brain works. It combines four blood results with a brief cognitive test. Ammonia shows the toxin load in your blood. Bilirubin and INR show how well your liver is clearing waste and making clotting factors. Creatinine shows how well your kidneys are working. The cognitive test adds a direct measure of your current thinking and attention. Your care team puts these into a set formula to get one number. A lower score suggests lower risk, and a higher score suggests a greater chance of significant HE.
What is a normal HAST/HASA score?
A score below 10 is the lowest risk band. It means minimal risk of HE, normal cognitive function, and usually routine monitoring. A score of 10 to 20 means intermediate risk. Some cognitive changes or subtle HE may be present, so your doctor may suggest closer monitoring and possible interventions. A score above 20 means high risk. It points to worsening brain function and usually calls for urgent evaluation and treatment. These bands are a guide, not a verdict. Discuss your specific result with your doctor, who will read it with your symptoms and medical history.
Is the HAST/HASA score the same as the West Haven Criteria?
No. The two tools do different jobs. The HAST/HASA score estimates your risk of HE using blood tests and a cognitive test. The West Haven Criteria grades how severe HE is once it is present. It describes mental status from minimal changes (covert HE) through confusion and coma (overt HE, grades I to IV). Doctors often use both together. The HAST/HASA score can flag rising risk, and West Haven grading can describe how severe an episode actually is.
Why does the score include more than just ammonia?
Ammonia alone does not give a reliable answer. An elevated ammonia level does not confirm HE, and a normal level does not fully rule it out once symptoms are present. For that reason, the HAST/HASA score adds other information. Bilirubin and INR show how well your liver is working. Creatinine shows how well your kidneys clear toxins. A cognitive test shows how your brain is working right now. Ammonia carries the largest weight in the formula, but the other inputs give your care team a fuller picture.
Can my HAST/HASA score change with treatment?
Yes. The score comes from blood tests and a brief cognitive assessment, so your doctor can safely recalculate it as often as needed. Comparing results over time can show whether treatments such as lactulose, rifaximin, or dietary changes are lowering your risk. The score can also rise. HE is often triggered by an infection, gastrointestinal bleeding, constipation, dehydration, or a new sedating medication. If your score goes up, your care team will typically look for and treat one of these triggers and may adjust your HE therapy.
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.