Hepatitis C: Frequently Asked Questions About Diagnosis

Diagnosis and Testing

What Is Hepatitis C?

Hepatitis C is a liver disease caused by the hepatitis C virus (HCV), which is found in the blood of persons who have this disease. HCV is spread by contact with the blood of an infected person.

What Blood Tests Are Available to Check for Hepatitis C?

There are several blood tests that can be done to determine if you have been infected with HCV. Your doctor may order just one or a combination of these tests. The following are the types of tests your doctor may order and the purpose for each:

Anti-HCV (antibody to HCV)

• EIA (enzyme immunoassay)
  This test is usually done first. If positive, it should be confirmed
• RIBA (recombinant immunoblot assay)
  A supplemental test used to confirm a positive EIA test

Anti-HCV does not tell whether the infection is new (acute), chronic (long-term) or is no longer present.

Qualitative tests to detect presence or absence of virus (HCV RNA)

• Generic polymerase chain reaction (PCR)
• Amplicor HCV™

Quantitative tests to detect amount (titer) of virus (HCV RNA)

• Amplicor HCV Monitor™
• Quantiplex HCV RNA (bDNA)

PCR and other tests to directly detect virus are not licensed tests and are only available on a research-basis. A single positive PCR test indicates infection with HCV. A single negative test does not prove that a person is not infected. Virus may be present in the blood and just not found by PCR. Also, a person infected in the past who has recovered may have a negative test. When hepatitis C is suspected and PCR is negative, PCR should be repeated.

Can You Have a "False Positive" Anti-HCV Test Result?

Yes. A false positive test means the test looks as if it is positive, but it is really negative. This happens more often in persons who have a low risk for the disease for which they are being tested. For example, false positive anti-HCV tests happen more often in persons such as blood donors who are at low risk for hepatitis C. Therefore, it is important to confirm a positive anti-HCV test with a supplemental test as most false positive anti-HCV tests are reported as negative on supplemental testing.

Can You Have a "False Negative" Anti-HCV Test Result?

Yes. Persons with early infection may not as yet have developed antibody levels high enough that the test can measure. In addition, some persons may lack the (immune) response necessary for the test to work well. In these persons, research-based tests such as PCR may be considered.

How Long after Exposure to HCV Does It Take to Test Positive for Anti-HCV?

Anti-HCV can be found in 7 out of 10 persons when symptoms begin and in about 9 out of 10 persons within 3 months after symptoms begin. However, it is important to note that many persons who have hepatitis C have no symptoms.