Hepatitis C: The Basics : How is it diagnosed, and what tests are used?
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How is it diagnosed, and what tests are used?

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. As discussed above, however, about 15 to 25 percent of people who are initially infected with the virus are able to clear the virus from their bodies, usually within six months of exposure. The next step is to look for the actual virus in the bloodstream, using a test called PCR. If a person was infected with HCV very recently, called acute infection, he or she may not yet have antibodies, in which case a PCR test is necessary to confirm infection.

HCV Viral Load Testing: To look for HCV, a health care provider can request a qualitative PCR test to determine whether or not the virus is in a person’s bloodstream. A health care provider can also order a quantitative PCR or bDNA test to check for the presence of HCV and to figure out the person’s HCV viral load (the amount of HCV in a measurement of blood).

The HCV viral load is a very important laboratory test. Though the HCV viral load test cannot determine if or when someone with hepatitis C will develop cirrhosis or liver failure, it can help determine how likely it is someone will respond to treatment. As a rule of thumb, the lower the HCV viral load, the better someone’s chances of responding to HCV treatment.

HCV viral load testing is often used during treatment to determine how well therapy is working.

HCV Genotypic Testing: Genotype refers to genetic structure or makeup of living organisms. The hepatitis C virus has more than six different genotypes, which are numbered in the order of their discovery. Each of these genotypes has many 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 both the type of treatment, and the length of treatment; HCV genotype also helps to predict the likelihood of curing HCV.  

Worldwide, HCV genotype 1 is most common, accounting for 60 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 US, and other genotypes are rare. 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 1993 (when effective screening procedures were instituted).

IL-28B Genotypic Testing: Interleukin-28B (IL-28B) is a human gene that plays a role in the immune system's defense against certain viruses. Certain inherited changes, or polymorphisms, in the gene have been linked to higher (or lower) cure rates in people with HCV genotype 1 using one of the most important drugs used to treat the virus: Pegylated interferon alpha.

Since everyone gets a gene from each parent, a person can have an IL28B "CC", "CT" or "TT" genotype. People with the IL28B CC genotype are more likely to be cured by HCV treatment than people with the TT genotype; cure rates among people with the CT genotype fall somewhere in between. Apparently, the IL28B TT genotype is common among African Americans; it clearly contributes to lower cure rates

Knowing this information can be helpful to you and your doctor when discussing treatment options, especially with new medications that aren't affected by the IL-28B gene becoming available.

Liver Function Tests: Because hepatitis C is a liver disease, you and your doctor will want to monitor your liver’s health. The easiest way to do this is to have regular blood tests that measure the levels of liver enzymes. When hepatocytes (liver cells) become damaged by HCV, these enzymes can become elevated. Some tests to know:

Liver Function Tests
Alanine aminotransferase (ALT; sometimes listed as "SGPT"): About two thirds of people with chronic hepatitis C have continuously elevated ALT levels, reflecting ongoing damage to liver cells. In one third of people with chronic hepatitis C, the ALT levels remain normal, even though they have a detectable HCV viral load. Although most of these people will live with HCV infection without any liver-related problems, roughly one quarter of people may have progression of liver disease even when ALT levels are normal. ALT, in particular, is often one of the criteria in deciding when to start HCV treatment.
Aspartate aminotransferase (AST; sometimes listed as "SGOT"): AST levels are often elevated in people with chronic hepatitis C. However, AST levels are usually lower than ALT levels. If cirrhosis occurs, AST levels can increase higher than ALT levels—a sign that damage to the liver is worsening.
Alkaline phosphatase and gamma glutamyl transpeptidase (GGT or GGTP): These levels are usually normal. However, they may become elevated if hepatitis C progresses to cirrhosis.


Liver Biopsy: Unfortunately, liver enzymes do not tell the whole story regarding the health of the liver. Measuring HCV viral load and liver enzyme levels in the blood cannot determine if—and how much—damage has actually been done to the liver. For this, a liver biopsy is needed. A biopsy allows experts to examine actual tissues taken from the liver. Not only can this determine how healthy the liver really is, but it can also help you and your doctor figure out when to start treatment for hepatitis C.

A liver biopsy is often performed, on an outpatient basis, in a hospital. Sometimes, a trained health care provider—such as a hepatologist or a gastroenterologist—can perform a liver biopsy in his or her office. An ultrasound or “echo” machine is sometimes used to identify the best location to make the biopsy. The patient lies quietly on his or her back or slightly to the left side. The area of the skin where the biopsy will be done is carefully cleaned. Then, a local anesthetic agent is used to numb the skin and tissue below. A specially designed thin needle is inserted through the skin. At this point, the physician will instruct the patient to take a deep breath and to hold it for about five seconds. The needle is advanced into and out of the liver. This takes only one or two seconds. A slender piece of tissue is removed with the needle and is then processed through a laboratory. The entire procedure from start to finish lasts only 15 to 20 minutes. The patient will then be instructed to lie still for several hours. There may be some discomfort in the chest or shoulder, but this is usually temporary. In rare cases, the provider conducting the procedure can “nick” a blood vessel, which can result in internal bleeding.

The results of the biopsy are usually available within a week and will be explained to you by your health care provider.

More recently, researchers have developed non-invasive methods for determining the extent of liver damage. There are blood markers that can help determine whether fibrosis is present. Unfortunately, they are accurate in determining only minor or major fibrosis, and not stages in between. A newer method, called transient elastography―which uses ultrasound and low frequency elastic waves to measure liver elasticity―has proved more accurate, especially when combined with blood markers, but researchers in the United States have not yet advocated for it to replace liver biopsies.


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Last Revised: December 04, 2014

This content is written by the Hep editorial team.

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