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Spotlight Series on Hepatitis C

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Hepatitis C FAQs for Health Professionals

May 31, 2015

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Testing and Diagnosis

Who should be tested for HCV infection?

HCV testing is recommended for anyone at increased risk for HCV infection, including:

  • Persons born from 1945 through 1965
  • Persons who have ever injected illegal drugs, including those who injected only once many years ago
  • Recipients of clotting factor concentrates made before 1987
  • Recipients of blood transfusions or solid organ transplants before July 1992
  • Patients who have ever received long-term hemodialysis treatment
  • Persons with known exposures to HCV, such as
    • health care workers after needlesticks involving HCV-positive blood
    • recipients of blood or organs from a donor who later tested HCV-positive
  • All persons with HIV infection
  • Patients with signs or symptoms of liver disease (e.g., abnormal liver enzyme tests)
  • Children born to HCV-positive mothers (to avoid detecting maternal antibody, these children should not be tested before age 18 months)

What blood tests are used to detect HCV infection?

Several blood tests are performed to test for HCV infection, including:

  • Screening tests for antibody to HCV (anti-HCV)
    • enzyme immunoassay (EIA)
    • enhanced chemiluminescence immunoassay (CIA)
  • Qualitative tests to detect presence or absence of virus (HCV RNA polymerase chain reaction [PCR])
  • Quantitative tests to detect amount (titer) of virus (HCV RNA PCR)
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How do I interpret the different tests for HCV infection?

A table on the interpretation of results of tests for Hepatitis C Virus (HCV) infection and further actions is available at www.cdc.gov/hepatitis/HCV/PDFs/hcv_graph.pdf [PDF - 1 page].

Is an algorithm for HCV diagnosis available?

A flow chart that outlines the serologic testing process beginning with anti HCV testing is available at www.cdc.gov/hepatitis/HCV/PDFs/hcv_flow.pdf [PDF - 1 page].

How soon after exposure to HCV can anti-HCV be detected?

HCV infection can be detected by anti-HCV screening tests (enzyme immunoassay) 4-10 weeks after infection. Anti-HCV can be detected in >97% of persons by 6 months after exposure.

How soon after exposure to HCV can HCV RNA be detected by PCR?

HCV RNA appears in blood and can be detected as early as 2-3 weeks after infection.

Under what circumstances is a false-positive anti-HCV test result likely?

False-positive anti-HCV tests appear more often when persons at low risk for HCV infection (e.g., blood donors) are tested. Therefore, it is important to follow-up all positive anti-HCV tests with a RNA test to establish current infection.

Under what circumstances might a false-negative anti-HCV test result occur?

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

Can a patient have a normal liver enzyme (e.g., ALT) level and still have chronic Hepatitis C?

Yes. It is common for patients with chronic Hepatitis C to have liver enzyme levels that go up and down, with periodic returns to normal or near normal levels. Liver enzyme levels can remain normal for over a year despite chronic liver disease.

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This article was provided by U.S. Centers for Disease Control and Prevention. Visit the CDC's website to find out more about their activities, publications and services.

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