This test determines the amount of the enzyme ALAT in blood. An enzyme is a protein that helps cells convert one substance into another.
ALAT is present primarily in the liver. Smaller amounts are found in the kidneys, heart, and muscles. Normally, the amount of ALAT in the blood is low. When liver cells are damaged, ALAT leaks from the liver into the blood. As a result, the amount of ALAT in the blood rises. This can happen before there are any symptoms or signs (such as jaundice, yellow eyes, or yellow skin) that indicate liver damage.
In people who do not have liver disease, ALAT activity is less than 45 U/l in men and less than 35 U/l in women. Slightly elevated values, without symptoms, are not immediately assigned a significance. Only when the value is more than twice the stated upper limit is further investigation into the cause desirable.
In chronic liver inflammation ALT is elevated (up to 5 times higher than normal) but not as much as in acute hepatitis. The doctor will then usually request the test more often to see if enzyme activity of ALAT changes or stays the same. In some, also serious, liver diseases such as dying liver tissue (liver cirrhosis), liver cancer and closure of the bile ducts, it happens that the ALAT value is still normal or only slightly elevated. Therefore, ALAT is often combined with other liver tests such as AF and ASAT.
A strongly elevated ALAT enzyme activity (more than 15x higher than normal) is almost always caused by acute inflammation of the liver (acute hepatitis). This form of hepatitis is usually caused by a viral infection. In acute hepatitis, ALAT remains highly elevated for as long as 1 to 2 months. The results only return to normal after 3 to 6 months.
For a more complete overview, you can also choose the liver disease combination examination or a general medical check-up.