Before answering this question, it may be helpful to review some of the things that happen after a person is infected with HCV. Shortly after a person is infected with HCV, the virus spreads through their body, and their immune system produces substances called antibodies in response to the infection. Some HCV-infected persons are able to clear the virus from the body naturally, while others go on to develop chronic (long-lasting) HCV infection. In either case, they will continue to have HCV antibodies.
Typically, a person who undergoes HCV testing first gets a test that looks for HCV antibodies. Although a positive (reactive) antibody test result indicates that a person has been infected with HCV in the past, it does not show whether they cleared the virus or remain chronically infected. Consequently, when a person has a positive result on an HCV antibody test, it is recommended that they have an HCV RNA test. This test looks for HCV viral genetic material (RNA), which is evidence that the person has an active HCV infection.
Persons who have a negative (nonreactive) result on an HCV antibody test are considered not infected with HCV. They generally do not need to undergo further HCV testing, unless they have a known risk factor for a false-negative test result. Factors that may lead to a false-negative HCV antibody test result include a recent HCV infection, chronic hemodialysis, or an immune compromising condition.
People who have a positive HCV antibody test and a positive HCV RNA are considered to have current (active) HCV infection. In contrast, if a person has a positive HCV antibody test result and a negative HCV RNA result, they are considered to have no evidence of current HCV infection. In such cases, additional testing can help determine whether the positive antibody test result is a false-positive or is an indication of a past HCV infection that the body has cleared.
The window period for an HCV test is the amount of time from when a person is first infected with the virus and the appearance of detectable evidence of their HCV infection, such as HCV antibodies or viral genetic material. Most people develop detectable HIV antibodies within 8 to 12 weeks after becoming infected. For most people who would like to get tested for HCV, it is generally a good idea to wait until after this window period before having an HCV antibody test.
However, if someone has had many risks over a long period of time—for example, a person who injects drugs and shares needles—they may want to have an HCV antibody test even if it has been less than 12 weeks since their last potential exposure to the virus. If this initial test is negative, they might want to get retested later.
The Centers for Disease Control and Prevention (CDC) estimates that as many as three out of four people who are infected with HCV don’t know that they are infected.
CDC recommends testing for:
- “Baby Boomers” (persons born between 1945 and 1965), who have HCV infection rates 5 times higher than in other age groups;
- People living with HIV;
- People with known exposures to HCV;
- People who have ever injected illegal drugs; and
- People who received blood transfusions or solid organ transplants before July 1992.
HCV testing is also recommended for:
- Recipients of clotting factor concentrates made before 1987;
- Patients who have ever received long-term hemodialysis treatment;
- Patients with signs or symptoms of liver disease, such as abnormal liver enzyme test results; and
- Children born to mothers who test positive for HCV.
Yes. As mentioned earlier, if a person has a positive antibody test, they should then have an HCV RNA test. This type of test looks for evidence of the virus itself, rather than antibodies. If this RNA test has a negative result, it indicates that the person has cleared the virus and is no longer infected. If the RNA test result is positive, it indicates that the person still has active HCV infection.
Once it has been determined that someone has chronic HCV infection, other tests will likely be performed on a regular basis. These tests, which include liver enzyme (ALT and AST) and viral load tests, are done periodically to monitor how that person’s liver is functioning and how quickly the HCV is making more copies of itself (replicating). However, these blood tests do not clearly show whether HCV is causing significant liver damage. Sometimes an ultrasound and/or a liver biopsy is performed to get a clearer picture of the liver’s health.
Until recently, liver biopsies were considered the best way to determine whether, and to what extent, liver damage occurred in persons infected with HCV. However, in 2013, the U.S. Food and Drug Administration approved FibroScan, a device that uses ultrasound to provide a noninvasive assessment of liver fibrosis (scarring). Recent studies have shown that FibroScan assessments of liver fibrosis are comparable with those provided by liver biopsies. This is good news, because it means that a noninvasive, outpatient, 15-minute procedure can often take the place of a liver biopsy, which is painful and carries the risk of bleeding and infection.
If you have specific questions about HCV testing or other HCV-related health issues, please contact AIDS Action’s Health Library at 617.450.1432 or visit the Health Library page.