Tests for Hepatitis C

Hepatitis C is a condition in which the body’s liver becomes inflamed. There are several harmful agents that may damage the liver. The inflammation is a response by the body to fight these agents. It may be caused by death or disease to the liver cells, which, in turn, causes a response by the body.

The body’s inflammatory response helps to kill the hepatitis C virus. An extremely strong reaction, or high level of inflammatory response, may extensively damage the liver, resulting in a fatal outcome. On the other hand, a very weak reaction may not eliminate the virus, and a chronic infection and significant damage may result.

Testing

Clinicians will use antibody tests to screen and diagnose patients for hepatitis C infection. People who need to be screened include those who are asymptomatic but who may have risk factors, as well as those who have symptoms associated with liver disease or hepatitis, or those who have been exposed to the virus.

Risk factors include:

  • the use of poorly cleaned, used syringes and needles
  • receiving transfusions of blood from those who are infected with hepatitis C

The hepatitis C antibody test may read positive in some people, even if the infection has already been cleared from their system. In addition, "weakly positive" test results may actually be false positive results. For these reasons, the US Centers for Disease Control and Prevention (CDC) recommends that any positive antibody tests be followed by a hepatitis C RNA test. This will be administered to anyone who has a positive reading on their antibody test.

Hepatitis C RNA Test

The RNA test will be positive if there is any hepatitis C genetic material in the sample. A positive RNA test result indicates that the virus is still in the system, and that the patient may require treatment. The treatment regimen will be guided by the results of the hepatitis C genotype test, which will reveal the exact virus strain infecting the body. The test is also useful to screen for past exposure, as well as any current infection. The diagnostic determines the presence of antibodies to the virus, which in turn reveals any exposure to hepatitis C.

Quantitative and Qualitative Testing

The hepatitis C RNA test may be quantitative, which determines the number of viral RNA particles in the blood sample. It will confirm the virus and detect an active infection. This type of viral load testing also helps determine the degree of success of the treatment regimen. If treatment is successful, there will occur a decrease of at least 99% in the viral load soon after treatment began, possibly within a month, and it often results in a non-detectable viral load. The American Association for the Study of Liver Diseases and the Infectious Disease Society of America guidelines indicate that if the viral load in the blood is undetectable three months after the end of treatment, it means that the hepatitis virus infection has responded to therapy.

The RNA test is also qualitative, in that it helps determine if the infection is current, and if there were any past infections. Viral genotyping can determine the genotype of the hepatitis C present. There exist five types of hepatitis C which are most commonly responsible for infection in humans, and more than 50 subtypes. The most common is genotype 1, which causes three-quarters of hepatitis C cases in the US. Different genotypes of the infection may require treatment with different drugs.

The results of viral load testing are shown as a number if the virus is in the body. If there is no virus, or if the level is too low for a determination, the result will be indicated as negative or undetectable. Generally, if the antibody test is positive, the patient will have been infected at some point. If the RNA test is positive, then the patient is currently infected. If no viral RNA is found, the patient is not infected, or the virus is present in very low numbers.

The antibody testing may be one component of an overall acute viral hepatitis panel required to test for the most common hepatitis viruses that are causing symptoms. In addition, there may be the need for a liver function panel, which will assess liver health.

Reviewed by Liji Thomas, MD.

References:

Further Reading

Last Updated: Sep 4, 2017

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