Liver Function Tests Explained

Interpreting your liver function tests results can be challenging, because your liver affects so many different bodily functions. When testing for liver malfunction, your doctor will probably conduct a series of tests, such as blood tests, imaging tests and liver biopsies. All of these tests can tell your doctor something about what is going on in your body, but it will take a compilation of test results to accurately diagnose what is going on with your liver. Your best bet is to ask a lot of questions of your doctor when you have your follow up exam so you can get a clear picture of what all the liver function tests are saying about your liver health.

When your doctor mentions liver function tests, he's talking about blood tests. The following explanations may help you interpret your liver function test results, although your doctor will be the one who can truly explain what the numbers mean for you.

Liver Enzymes
Most liver function tests look for abnormalities in levels of four enzymes: apartate aminotransferase (AST), alanine aminotransferase (ALT), gamma glutamyl transpeptidase (GGT) and alkaline phosphatase (AP). In general, high levels of AST or ALT-over 40 IU/L of AST and over 45 IU/L of ALT-are red flags of poor liver function. High levels of GGT-over 60 IU/L of GGT-or of ALP-over 115 IU/L of GP-are usually indicators that there is some sort of problem with bile production or flow.

When examining these levels, your doctor will take into account for the fact that some races and genders have higher or lower normal ranges of these enzymes, as well as the fact that high levels of these enzymes don't necessarily mean the liver is not functioning up to par since some of these enzymes are also produced by the kidneys or can be overproduced if alcohol was consumed within a certain amount of time.

Blood Ammonia
If you have high levels of ammonia in your blood, it may mean you have encephalopathy, but many doctors do not even do this test anymore. Because there are so many other factors that can increase the level of ammonia in your bloodstream, this test might not necessarily be the most accurate. Smoking, certain prescription medications and any kind of delay in interpreting the results can skew the numbers for this test.

Your doctor may test your bilirubin levels to determine if your liver is not properly recycling old red blood cells. If your bilirubin levels are over 1/mg/dl, your doctor may be concerned.

Blood Clotting Tests
Because your liver is responsible for producing platelets for your blood, your doctor may conduct blood clotting tests or do a platelet count. However, neither of these tests can conclusively point to liver damage.

As you can see, your doctor will need to use the results of these tests in conjunction with other tests and exams to properly diagnose your condition. Several of these tests can be thrown off by other factors, so be patient with your doctor as he wades through the test results and figures out exactly what the best diagnosis and treatment options will be.

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