Icon responsive menu red

  Back Blood-tests Explained


Hepatitis C


At a Glance

Why Get Tested?

To screen for and diagnose a hepatitis C virus (HCV) infection and to monitor treatment of the infection

To learn more about hepatitis C, read the article on Viral Hepatitis.

When to Get Tested?

For screening: when you have risk factors for HCV infection or were born between 1945 and 1965, per 2012 CDC recommendations

For diagnosis: when you may have been exposed to the hepatitis C virus, such as through contact with infected blood, or have symptoms associated with liver disease

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

Hepatitis C (HCV) is a virus that causes an infection of the liver that is characterized by liver inflammation and damage. Hepatitis C tests are a group of tests that are performed to detect, diagnose, and monitor the treatment of a hepatitis C viral infection. The most common test for HCV looks for antibodies in the blood that are produced in response to an HCV infection. Other tests detect the presence of viral RNA, the amount of viral RNA present, or determine the specific subtype of the virus.

Hepatitis C is one of five hepatitis viruses identified so far, including A, B, D, and E, that are known to cause the disease. HCV is spread by exposure to contaminated blood, primarily though the sharing of needles by intravenous drug users, but also by sharing personal items contaminated by blood such as razors, through sex with an infected person, via healthcare occupational exposure, and, less commonly, from mother to baby during childbirth. Before tests for HCV became available in the 1990s, HCV was often transmitted by blood transfusions.

While HCV is not as contagious as hepatitis B, there is currently no vaccine to prevent infection. Hepatitis C infection is a common cause of chronic liver disease in North America. The Centers for Disease Control and Prevention (CDC) estimates that there were approximately 30,500 cases of acute hepatitis C in the U.S. in 2014 and that there are 2.7 to 3.9 million people in the U.S. living with chronic hepatitis C.

Many of those who are infected have no symptoms and are not aware of the condition. The acute HCV infection may cause few to mild nonspecific symptoms, and the chronic infection may simmer quietly for a decade or two before causing sufficient liver damage to affect liver function.

Hepatitis C infections cause increased risk of developing some other serious conditions:

  • About 75-85% will develop chronic HCV infection.
  • About 5-20% will develop cirrhosis over 20 years; recent projections suggest that almost 45% will eventually develop cirrhosis.
  • HCV causes death in about 1-5% of those chronically infected who develop cirrhosis or liver cancer.

Hepatitis C antibody tests are used to screen individuals for the infection, including, for example, people with no signs or symptoms but with risk factors, people who have symptoms associated with hepatitis or liver disease, or those who have been exposed to the virus.

Since the antibody test can remain positive in most people even if they have cleared the infection, a positive antibody test is followed by a hepatitis C RNA test, which detects genetic material of the virus. A positive result on the RNA test means the virus is present, the infection has not resolved, and the person may require treatment. The hepatitis C genotype test determines which strain of virus is present to help guide treatment.

Healthcare practitioners may also order a liver panel, which is a group of tests that help assess the health of the liver.

How is the sample collected for testing?

A blood sample is drawn by needle from a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

Hepatitis C tests are used to screen for and diagnose a hepatitis C virus (HCV) infection, to guide therapy and/or to monitor the treatment of an HCV infection.

An HCV antibody test is used to screen for past exposure and current infection. It detects the presence of antibodies to the virus, indicating exposure to HCV. This test cannot distinguish whether someone has an active or a previous HCV infection. There is some evidence that if the test is "weakly positive," it may be a false positive. The Centers for Disease Control and Prevention (CDC) recommends that all positive antibody tests be followed by an HCV RNA test that detects viral RNA in the blood to determine whether or not the person has an active infection.

The HCV antibody test may be performed as part of an acute viral hepatitis panel to determine which of the most common hepatitis viruses is causing a person's symptoms.

The following tests may be used to diagnose a current infection and to guide and monitor treatment:

  • HCV RNA tests:
    • HCV RNA test, Quantitative (HCV viral load) detects and measures the number of viral RNA particles in the blood. This test may be used to confirm the presence of the virus and diagnose an active infection. Viral load tests are also used before and during treatment to help determine response to therapy by comparing the amount of virus before and during treatment.
    • HCV RNA, Qualitative is used to distinguish between a current or past infection. It is reported as a "positive" or "detected" if any HCV viral RNA is found; otherwise, the report will be "negative" or "not detected." This test is not frequently used any more.
  • Viral genotyping is used to determine the kind, or genotype, of the HCV present to help guide treatment. There are 5 major types of HCV and more than 50 subtypes identified; the most common, genotype 1, accounts for about 75% of cases in the U.S. The drugs selected for treatment depend in part on the genotype of HCV infecting a person.

When is it ordered?

The CDC recommends screening for HCV infections with an HCV antibody test when people:

  • Have ever injected illegal drugs
  • Received a blood transfusion or organ transplant before July 1992*
  • Have received clotting factor concentrates produced before 1987
  • Were ever on long-term dialysis
  • Are children born to HCV-positive women
  • Have been exposed to the blood of someone with hepatitis C
  • Are healthcare, emergency medicine, or public safety workers who had needlesticks, sharps, or mucosal exposure to HCV-positive blood
  • Have evidence of chronic liver disease
  • Have HIV
  • Were born between 1945 and 1965, regardless of other risk factors for HCV

*The blood supply has been monitored in the U.S. since 1992, and any units of blood that test positive for HCV are rejected for use in another person. The current risk of HCV infection from transfused blood is about one case per two million transfused units.

HCV antibody testing may be done when someone has abnormal results on a liver panel, for example, or signs and symptoms associated with hepatitis. In these cases, it may be done as part of an acute hepatitis panel. Most people newly infected with HCV have no symptoms or ones that are so mild that they rarely prompt a person to visit a healthcare provider and get tested for HCV. However, about 10-20% of people may experience signs and symptoms such as fatigue, pain in the abdominal area, decreased appetite, and jaundice.

An HCV RNA test or viral load is ordered as follow-up testing when an antibody test is positive to confirm an active infection. Some laboratories will automatically perform this test if the HCV antibody test is positive.

HCV genotyping is done when a person has been diagnosed with an HCV infection and is often ordered before treatment is started to guide treatment selection.

HCV viral load testing may be ordered at the start of treatment, periodically to monitor response to treatment, and after the completion of treatment to evaluate its effectiveness.

What does the test result mean?

An HCV antibody test is typically reported as "positive" or "negative."

Results of HCV viral load testing are reported as a number if virus is present. If no virus is present or if the amount of virus is too low to detect, the result is often reported as "negative" or "not detected."

Interpretation of the HCV screening and follow-up tests is shown in the table below. In general, if the HCV antibody test is positive, then the individual tested is infected or has likely been infected at some time with hepatitis C. If the HCV RNA test is positive, then the person has a current infection. If no HCV viral RNA is detected, then the person either does not have an active infection or the virus is present in very low numbers.

HCV Antibody HCV RNA HCV Infection
Negative   No infection or too early after exposure for the test to be accurate; if suspicion remains high, retesting at a later time may be required.
Positive or Indeterminate Negative Past infection or no infection (false-positive screen); additional testing if indicated
Positive or Weak or Indeterminate Positive Current infection

For monitoring purposes, an HCV viral load (HCV RNA quantitative) can indicate whether or not treatment is effective. A high or increasing viral load may be a sign that treatment is not successful whereas a low, decreasing, or undetectable viral load may imply that the treatment is working.

Successful treatment causes a decrease of 99% or more in viral load soon after starting treatment (as early as 2-4 weeks) and usually leads to undetectable viral load after treatment is completed. According to guidelines from the American Association for the Study of Liver Diseases and the Infectious Disease Society of America, an undetectable viral load in a treated person's blood 12 weeks after the end of the treatment means that the HCV infection has responded to therapy.

The results of the HCV genotype test identifies which strain of HCV the person has and helps guide the selection and the length of treatment. Treatments may differ depending on a variety of factors, including HCV genotype and the health of the person's liver (see Common Questions #5.)

Is there anything else I should know?

HCV antibodies usually do not appear until several months after exposure but will always be present in the later stages of the disease.

About 25% of those with HIV/AIDS also have an HCV co-infection, and their liver disease is likely to progress at an accelerated rate.



Disclaimer:

MedSquirrel is a shared knowledge, collective intelligence digital platform developed to share medical knowledge between doctors and patients. If you are a healthcare practitioner, we invite you to criticise, contribute or help improve our content. We support collaboration among all members of the healthcare profession since we strive for the provision of world-class, peer-reviewed, accurate and transparent medical information.

MedSquirrel should not be used for diagnosis, treatment or prescription. Always refer any questions about diagnosis, treatment or prescription to your Doctor.