Understanding False Positive, False Negative Hepatitis C Testing

Blood tests can seem confusing with hepatitis C, especially if you’ve been told you had a false positive or false negative test. You may wonder, "What does that mean? Do I have hepatitis C or not?" Let’s explain.

Antibody testing

Normally, the first blood test for hepatitis C is called an anti-HCV test. This test is looking for the presence of antibodies from the hepatitis C virus. Antibodies occur if you have been exposed to the virus. This means that people who currently have the virus will test positive, but also means that those who have cleared the virus in the acute stage (less than 6 months) may also test positive.

Antibodies for hepatitis C also are present after you have been treated for hepatitis C and the virus itself shows to be undetected. Antibodies are like a fingerprint, showing the presence of the virus was once there.

False positive test

A false-positive test result means it looks like the test is positive, indicating you may have the virus when you really don’t. This result can happen with patients who are at low-risk for the hep C infection, such as blood donors or a patient with an autoimmune disorder. A false-positive test in newborns can often occur occur because infants carry the antibodies from the mother, even though they may not have the virus.

If you receive a positive test, a follow-up test is done to confirm the presence of HCV antibodies in your blood; This second test (typically, a qualitative HCV-RNA test) will confirm if you really have hepatitis C. Later, a quantitative HCV-RNA test can be used to measure the amount of virus in the blood.

False negative test

A person who is newly exposed to the virus may receive a false negative antibody test if the antibodies have not developed an amount high enough to be measured. In some cases, some patients may not have the immune response necessary to give a proper reading. It can sometimes take 6 to 8 weeks for the body to produce enough antibodies to be detected in an antibody test.

HCV RNA PCR testing

Early testing with HCV RNA PCR, which looks at the genetic makeup of the virus, not only shows the presence of the virus, but means early diagnosis and treatment can be given before liver damage occurs. An HCV RNA PCR test can detect the hepatitis C virus as soon as 1 to 2 weeks from infection.

If someone is at high risk for exposure to the hepatitis C virus or knows they have been exposed to the virus, even if they do not show symptoms, the physician can order the HCV-RNA test to confirm and see the amount of virus present in the blood.

For many patients, the symptoms for hepatitis C may not appear until much later, until liver damage is already present. Not all patients have symptoms or know they have hepatitis C. Consider asking your doctor if you should be tested for hepatitis C, and the different testing options, even if you do not have any symptoms.