Liver and pancreas
ASAT
An enzyme from the liver, heart and muscles that, together with ALAT, shows whether liver cells are damaged and how severely.
Everything about this testWhat it measures
ASAT (aspartate aminotransferase) is an enzyme found in liver cells, but also in heart and skeletal muscle and in red blood cells. When these cells are damaged, ASAT enters the blood. Because ASAT does not come only from the liver, the value is almost always assessed together with ALAT: ALAT is more specific for the liver, while ASAT says something about the severity and helps in finding the cause. The ratio between ASAT and ALAT gives a clue: in fatty liver disease and viral hepatitis, ALAT is usually higher than ASAT; in alcohol-related damage and advanced liver disease, it is often the other way around.
- Damage to liver cells, together with ALAT
- A clue that alcohol is the cause: ASAT higher than ALAT
- Damage to muscle tissue, for example after heavy exercise or with a muscle disease (creatine kinase is the better test for this)
High
A raised ASAT together with a raised ALAT fits damage to the liver cells, with the same causes as for ALAT: fatty liver disease, alcohol, viral hepatitis, medicines. If ASAT is raised while ALAT is normal, the enzyme often comes not from the liver but from the muscles: after heavy exercise or strength training, after a fall or muscle injury, with a muscle disease or with a heart attack. A sample in which red blood cells have broken down (hemolysis), for example after a difficult blood draw or a finger prick, also gives a falsely raised ASAT. Anabolic steroids raise both ASAT and ALAT. Symptoms that go with liver damage: tiredness, pain in the upper right abdomen, dark urine, jaundice.
Low
A low ASAT has no significance. The value can be somewhat lower during pregnancy, with kidney dialysis and with a vitamin B6 deficiency, but the test is not used for that.
If your result is abnormal
The GP assesses ASAT together with ALAT and, if a muscle cause is suspected, requests creatine kinase. With a raised ASAT and ALAT without a clear cause, a repeat measurement follows after about 4 weeks without alcohol and after reviewing medicines; if the value stays raised, testing for hepatitis B and C and iron overload follows, and usually an ultrasound of the liver.
Reliability
ASAT is less specific for the liver than ALAT: muscle and heart cells also contain a lot of ASAT. The Dutch GP guideline (NHG) uses ALAT as the first liver test and ASAT mainly as an addition to assess the severity and the possible cause (alcohol, muscle). Apart from ALAT and creatine kinase, a slightly raised ASAT is hard to interpret and often temporary.
Limitations
- Heavy exercise, strength training or a muscle injury in the days before the blood draw raises ASAT; an injection into a muscle can do so too.
- Hemolysis in the tube (red blood cells broken down by a difficult blood draw, a tourniquet left on too long or a finger prick) gives a falsely raised value.
- Alcohol, medicines (including high-dose paracetamol, statins, antibiotics), anabolic steroids and supplements can raise the value.
- Reference values differ between laboratories; only compare results from the same laboratory.
How common is this
A slightly raised ASAT without symptoms is usually the result of fatty liver disease, alcohol or muscle strain. According to the Dutch GP guideline (NHG), fatty liver disease occurs in about 1 in 4 adults, and much more often in people with overweight or diabetes. Excessive alcohol use occurs in about 5 to 6 in 100 adults in the Netherlands, about twice as often in men as in women.
Who is this useful for
Useful as an addition to ALAT when a liver condition is suspected, with long-term heavy alcohol use (the ratio with ALAT then helps), with use of anabolic steroids or medicines that strain the liver, and to monitor a previously abnormal value. As a single test without ALAT, ASAT has little value. In strength athletes, a slightly raised ASAT is often muscle-related; in that case, preferably have blood drawn 2 to 3 days after the last heavy training session.
Downsides and risks
- An ASAT that is raised on its own after exercise or due to hemolysis is easily mistaken for a liver problem.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results