How hepatitis C testing works: Diagnostic tests
- All hepatitis C tests used in Canada require a blood sample, and the availability of different tests varies across regions.
- Two tests are usually required to confirm a current hepatitis C infection: a screening test and a confirmatory test.
- In some cases, it is recommended that a person have only a confirmatory test. This happens most often when a person is being tested for hepatitis C reinfection.
The hepatitis C testing process
In the case of a suspected new infection, two test results are usually required to confirm if someone currently has hepatitis C.
The first test is a screening test, which is an antibody test. This test detects antibodies in the blood to determine if a person has ever had a hepatitis C infection.
- A non-reactive (negative) screening test result indicates that the person does not have hepatitis C antibodies and has never had a hepatitis C infection. No further testing is usually performed.
- If the antibody test is reactive (positive), this means that the person has antibodies to hepatitis C and therefore has had a hepatitis C infection at some point in their life.
The antibody test alone cannot tell whether the person has a current hepatitis C infection. A person will test positive for hepatitis C antibodies if they have hepatitis C at present, but also if they had a hepatitis C infection in the past. In other words, people will still have hepatitis C antibodies even if they spontaneously cleared the virus in the past or if they were treated and cured.
The second test is a confirmatory test, which detects the hepatitis C virus itself. This test detects genetic material of the virus to determine if a person currently has a hepatitis C infection.
- If a confirmatory test result is non-reactive (negative), then the person does not have a current hepatitis C infection.
- If the person has a reactive (positive) confirmatory test result, they currently have a hepatitis C infection. However, if the infection is still in the acute phase, there is a chance that their body will clear it without treatment.
The confirmatory test is most often an RNA test (ribonucleic acid), which looks for the presence of genetic material of the virus in the blood. In some jurisdictions, a core antigen test is used as a confirmatory test that detects proteins that are part of the hepatitis C virus.
If a person has had a positive antibody test result in the past, they will test positive for hepatitis C antibodies every time they have another screening or antibody test.
There is no immunity against hepatitis C. If a person is cured of or has cleared hepatitis C they can still get it again. This is called reinfection. If there is a chance that a person might have become reinfected, it is recommended that they only have a confirmatory test and not an antibody test.
Although not common, hepatitis C can be passed from parent to child during pregnancy or childbirth. The testing of children is different from the testing of adults in terms of both timing and method. Children of a parent with hepatitis C who are tested for the virus before 18 months of age and while breastfeeding should receive an RNA test (rather than receiving a screening test first), as any hepatitis C antibodies in their blood would probably have been acquired from the pregnant parent with hepatitis C.
Types of tests used
All hepatitis C tests used in Canada require a blood sample. The following tests are currently used in Canada, although availability will vary across regions. All of these tests are very accurate at identifying markers of hepatitis C infection (e.g., antibodies or parts of the virus) in the blood.
Standard hepatitis C testing
Most commonly, a blood sample is drawn from a person’s vein and sent to a public health laboratory for hepatitis C testing.
For standard hepatitis C tests, a person is required to provide one blood sample for a screening test and, if the test is reactive and antibodies are detected, return to provide a second blood sample for the confirmatory test.
Reflex testing is an evolving method of testing that is intended to simplify the hepatitis C testing process by completing both the screening and confirmatory tests with one blood sample. This reduces the risk of someone not returning for their second test and being lost to follow-up. Reflex testing is only available in some jurisdictions in Canada.
Rapid or point-of-care (POC) testing
A hepatitis C rapid or point-of-care (POC) test is a screening test in which a blood sample is taken from a finger prick and tested immediately onsite. A person can be told their test result in about 20 to 40 minutes and connected to a confirmatory test more quickly than with standard testing. POC testing is only available in some locations in Canada.
Dried blood spot (DBS) testing
In dried blood spot (DBS) testing, a blood sample is collected from a finger prick, dried on a paper card and sent to a laboratory for analysis. DBS testing collects multiple spots of blood on one card and therefore can be used for both screening and confirmatory testing. Another benefit of DBS testing is that it can help to reach people in rural and remote regions. However, very few laboratories in Canada are currently able to process DBS testing cards.
Resources for service providers
- Hepatitis C Basics – eduCATIE online course
- Hepatitis C Testing – educCATIE online course
- Dried blood spot collection for hepatitis C and HIV testing in Canada – Prevention in Focus
Resources for clients
- 6 things to know about Hep C – CATIE brochure
- Hep C can be cured – CATIE brochure
- You can have hepatitis C and not know it – CATIE postcard