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Hepatitis C Laboratory Tests

February 24, 2014

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Several laboratory (blood) tests are used for hepatitis C (HCV). These include liver function tests, HCV viral load, genotype tests, the IL28B genetic test, and blood clotting tests.

Liver Function Tests

The lab tests called "liver function tests" do not measure how the liver functions. Instead, they measure the levels of enzymes found in the liver, heart, and muscles. Enzymes are proteins related to chemical reactions in living organisms.

High enzyme levels can indicate liver damage caused by medications, heavy alcohol intake, viral hepatitis, toxic fumes or recreational drug use. Liver enzyme test results can be difficult to understand. People with serious liver damage sometimes have normal liver enzyme levels.

Different patterns of these enzymes -- when some are elevated and others are normal -- are part of the information your health care provider uses to monitor liver health.

Liver function tests include:

Viral Load Tests

The viral load test counts how many HCV particles are in your blood. This is similar to the HIV viral load test (see Fact Sheet 125) but there are some important differences:

HCV Genotype Tests

There are more than six different types of HCV, identified by a number. There are also subtypes, which are given a letter. For example, there are genotypes 1a and 1b. They are identified by analyzing a blood sample to determine the genetic code of the virus. The most common type of HCV in North America is genotype 1. Genotypes 2 and 3 are much less common in North America.

The HCV genotypes and subtypes give health care providers important information for choosing treatments. For example, genotypes 2 and 3 are the easiest to treat with interferon.

IL28B Genetic Test

Researchers have recently discovered a link between a patient's genetic code and their response to standard treatment. The genetic code of a large group of patients with HCV genotype 1 was analyzed. Patients with a particular variety of the IL28B gene were more than twice as likely to respond well to the standard HCV treatment of interferon and ribavirin. The IL28B test may become an important tool to guide HCV treatment.

Blood Clotting Tests

Some tests might be used if you are going to have a liver biopsy (see Fact Sheet 672). With a biopsy, there is a risk of bleeding. Blood clotting tests measure how quickly the blood forms clots, which stop bleeding. Abnormal values on these tests may indicate advanced liver disease.

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