If you have any risk factors for hepatitis C, then the next step is to test for it. Initial testing for hepatitis C has three parts. The first test, the HCV antibody test, sees if you have been exposed to the virus. The second test is the viral load test, and it detects whether you were merely exposed or if you actually have hep C. If that test is positive, then a genotype test is done to find out what kind of hep C you have.
HCV Antibody Testing: Diagnosing hepatitis C begins with an antibody test. Antibodies to HCV can be detected in the blood, usually within two or three months after the virus enters the body. If a person is positive for HCV antibodies, he or she has been exposed to the virus in the past. About 15 to 25 percent of people who are initially infected with HCV are able to clear the virus from their bodies, usually within six months of exposure, so the next step is to look for the actual virus in the bloodstream, using a viral load test. If a person has an acute infection, meaning that he or she was recently infected with HCV, antibodies may not have formed yet, so a viral load is necessary to confirm infection.
HCV Viral Load Testing: A health care provider can request a qualitative HCV RNA test to determine if the virus is in a person's bloodstream. A medical provider can also order a quantitative HCV RNA test to figure out a person's HCV viral load (the amount of HCV in a measurement of blood). Various methods are used to detect HCV RNA, including TMA (transcription-mediated amplification), PCR (polymerase chain reaction), and bDNA (branched DNA). Qualitative viral load testing tends to be more sensitive than quantitative testing. Viral load testing using PCR or TMA are more sensitive than bDNA testing.
HCV viral load testing is used during treatment to determine how well the medications are working. Increases and decreases in HCV RNA do not correlate to disease progression, so the qualitative viral load test is not very useful outside of treatment. HCV viral load results cannot determine if or when someone with hepatitis C will develop cirrhosis or liver failure.
HCV Genotypic Testing: Genotype refers to the genetic structure or makeup of living organisms. The hepatitis C virus has seven different genotypes, which are numbered in the order of their discovery. Each of these genotypes has subtypes, which were lettered in the order that they were discovered. It is important to find out which hepatitis C genotype you have, because it determines the best treatment for you. HCV genotype also helps to predict the likelihood of curing HCV, but improved medications with high cure rates have made this less useful.
Worldwide, HCV genotype 1 is most common, accounting for 46 percent of cases. In the United States, 75 percent of all HCV infections are genotype 1; genotypes 2, 3 and 4 are less common in the United States, and other genotypes are rare. Genotype 7 was discovered in 2013 and there is only one known case. It is possible to infected with more than one HCV genotype; this is most likely among injection drug users, and people who received contaminated blood products before 1987 (when viral inactivation started), or a blood transfusion before July 1992 (when effective screening procedures were instituted).
Last Revised: March 13, 2017