2.1.1 Antibody Tests
Antibody tests indicate whether the body has been exposed to the virus and has produced antibodies to fight it. They do not determine whether or not someone still has the virus, or how long they’ve been infected. Antibody tests are the most common method of diagnosing hepatitis C. However, the test can show a false positive reaction and therefore confirmation is necessary by finding evidence that the hepatitis C virus is actually in the blood using the polymerase chain reaction (PCR).
HCV Polymerase Chain Reaction (PCR) tests came onto the market in late 1994. HCV PCR tests look for the presence of the virus. Information
gained from the HCV PCR can be useful in interpreting unclear antibody test results.
The HCV PCR cannot tell how long someone has been infected.
A tiny amount of your blood sample is separated into parts and cleaned. Some of the viral RNA is pulled out. This goes through the process of PCR. Part of the RNA specific to hepatitis C is pulled apart by heating it, and new copies are made of this area. This is done millions of times in just a couple of hours. Your sample can then be analyzed through many different methods, including being seen under a UV light, producing that pretty sheet of stripes that you see in forensic crime shows, Maury Povich and the OJ trial. (Viola Vatter, Victoria, BC)
There are at least three sets: two are the controls--a known HCV-positive sample and an HCV-negative sample; the other sample is you. If yours matches the positive sample, you have the virus.
A genotype is the “family” to which our specific virus belongs. Our genotype does not change, but we can be re-infected with a different genotype. The most common genotypes are: 1a, 1b, 1c, 2a, 2b, 2c, 3a, 3b, 4, and 5. 3a has the highest response rate to interferon. People with this genotype are generally younger in age, and usually IV drug users.
Genotype 1 patients need longer treatment in order to respond.
This is a test, not yet approved in Canada, which tells whether or not you will respond to interferon-based treatment. Right now clinical trials are stratified into arms, sometimes according to genotype, sometimes according to viral load, sometimes according to status as a non-responder/null-responder/relapse, etc. Many researchers believe that patients should also be divided according to IL-28B genotype (C/C vs. non-C/C) before they are randomized to different arms. (This is a human, not a viral genotype).
In a trial, it was shown that there could be a 10 to 20% difference in response rates especially at week 4, according to the patient’s IL28B genotype. The difference may be even higher in non-white patients. It has been discovered that C/C GT1 patients have improved early responses, as shown in 3 hypothetical trials, where the researchers re-stratified results obtained in other trials. This stratification is especially important in the early phase trials.
( www.clinicaloptions.com/Hepatitis/Conference%20Coverage/AASLD%202010/Tracks/HCV%20Treatment/C apsules/810.aspx )
Antibody tests are usually positive or negative, but sometimes they come back unclear. Tests that come back positive are redone to confirm that they are right. Unclear results are repeated and if still unclear, different types of blood tests are done.
If you get a positive test result and have no risk background (for example, blood transfusions or drug use) it’s a good idea to check with your doctor to make sure that the laboratory double checked the result by using confirmatory tests.
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|2.1.0 How is it Diagnosed?|
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