How is hepatitis C (HCV) diagnosed?

A number of blood tests will determine if someone is infected with HCV. They may include:

• an enzyme immunoassay, or EIA antibody test
• a recombinant immunoblot assay, or RIBA if the EIA is positive
• a PCR test to detect the presence of viral RNA, and second test to determine the amount, or titer of the virus in the blood
• a blood test to check platelet and white blood cell counts
• liver biopsy – some patients may also have a liver biopsy, which a physician performs using an ultrasound-guided thin needle placed in the abdomen. The physician extracts a very small piece of the liver via the needle, which our pathologists check to determine if the liver is damaged, and if so, to what extent.

General: When an individual is exposed to the hepatitis C virus (HCV), his or her body produces antibodies to the virus. These antibodies remain in the HCV-infected individual throughout his or her life, even if the virus is eliminated from the body naturally or following medical treatment. Antibodies are proteins produced by the body's defense system to fight against foreign agents called antigens. An antigen is a substance that is capable of causing an immune response. Patients who recover from HCV infection have a lower risk of reinfection, although HCV antibodies do not completely prevent reinfection.

Diagnostic testing: HCV may be detected within 1 to 2 weeks after infection. The diagnostic tests for HCV are divided into two categories: serological assays, which detect the antibodies to HCV in the serum or plasma, and molecular assays that detect, quantify, or characterize HCV RNA in an infected patient. Both blood and tissue samples taken from the infected patient may be used to perform the molecular assays. Serum is the liquid component of blood that does not contain clotting factors. Plasma is the liquid component of blood in which blood cells are suspended. Serological tests, which detect the anti-HCV antibodies, can be screening tests or confirmatory tests. Screening tests help identify blood samples that contain antibodies, while confirmatory tests confirm the presence of specific antibodies in the screened samples. The second or third line of tests is referred to as supplemental tests.

Liver enzymes: A blood test may be performed to check for elevated levels of liver enzymes contained in liver cells, such as alanine aminotransferase (ALT) and aspartate aminotransferase (AST). These enzymes leak into the bloodstream when liver cells are injured. The most common cause of elevation of ALT is chronic hepatitis C infection. Therefore, if routine blood tests reveal increased liver enzyme levels, such individuals must be clinically evaluated and tested for HCV using ELISA.

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Since many patients have no symptoms of hepatitis C (HCV), the Centers for Disease Control recommend baby boomers get a simple screening blood test for HCV. Watch this video featuring liver transplant surgeon Dr. Robert Brown to learn more.

Blood tests are needed to tell if you have hepatitis C.

A screening blood test, called an antibody test, shows if a person has ever been infected with the hepatitis C virus.

If the antibody test is positive, a follow-up RNA blood test is needed to see if a person is still infected with the hepatitis C virus.

A CDC study shows through health department reports that only 50% of adults who had a positive antibody test had a follow-up test reported. Without a follow-up test, people won't know if they are still infected with the hepatitis C virus.

(The presence of the CDC logo and CDC content on this page should not be construed to imply endorsement by the U.S. government of any commercial products or services, or to replace the advice of a medical professional. The mark “CDC” is licensed under authority of the PHS.)