There are 3 major tests for HCV.
1) The ELISA test detects antibody to the virus.
2) The RIBA test is the confirmatory test for HCV.
3) The Quantitative HCV PCR test, which measures the amount of virus
circulating in a person’s blood stream.
While the newer HCV antibody tests are better; false positive results still
occur, and further testing should be used to confirm the antibody
test. Abnormal liver function tests (LFTs) suggest chronic disease, but
there is no correlation between the level of the liver function tests and
how severe the disease is. Many physicians still assume there is
(especially primary care physicians), and this has led to complications
and even death because of misdiagnosis. Recent studies show that testing
for enzyme level elevation is not an accurate diagnostic for the presence
of hepatitis C (Digestive Disease Week 2000).
Before 1990 doctors could diagnose HCV only by ruling out other possibilities
(thus the old name for HCV “non-A, non-B hepatitis).
Hepatitis C antibodies may not develop for two to six months after infection,
so only two-thirds of patients who go to the doctor with possible
hepatitis C infection can be diagnosed with blood tests. Diagnosis may
have to exclude other possible causes such as HAV, HBV, cytomegalovirus,
Epstein-Barre virus infection, as well as non-viral liver problems such
as fatty liver, or alcohol or drug-related diseases.
Follow-up blood tests are very important in order to determine if the disease
has become chronic. The blood tests for antibodies are usually repeated
three and six months after the original illness.
Diagnosis is most commonly made after detecting an antibody to a portion of HCV in the blood. This indicates that the person was exposed to the virus and that their immune system made an antibody. The test can show false positive reactions and therefore confirmation is necessary by finding evidence that the Hepatitis C virus is actually in the blood using the polymerase chain reaction (PCR), an extremely sensitive test for viral RNA.
