Hepatitis C Tests
Updated on 7/21/09
Since many patients do not have symptoms from hepatitis C, diagnosis often occurs only after they are found to have abnormal liver enzymes during routine blood work, insurance physicals, or preoperative evaluations, for example. Patients may then be surprised by the diagnosis. Other patients may be tested because of specific risk factors, such as a remote history of blood transfusions or exposure to needles.
The hepatitis C antibody is detected in almost all people infected with hepatitis C. However, because the antibody takes weeks to months to develop, tests can be falsely negative, especially just after exposure. If the hepatitis C antibody is positive, the actual presence of virus should be confirmed through a polymerase chain reaction, or PCR, test.
This section contains more information on:
Liver Biopsy
This outpatient procedure uses a needle to obtain a small amount of liver tissue for examination by a pathologist under a microscope. Liver biopsy is the "gold standard" test in liver medicine because it allows a clinician to assess how extensive and advanced liver disease is. It also gives the clinician and pathologist the opportunity to evaluate whether liver disease might have other causes in a person whose blood work shows a hepatitis C infection. Serious risks from a liver biopsy include bleeding, infection, perforation of another organ such as the bowel, and puncture of the lung. These occur rarely, perhaps in 1 in 1,000 biopsies or less frequently.
The role of liver biopsy in the diagnosis and management of hepatitis C is somewhat controversial. Some clinicians recommend liver biopsy routinely to all patients with hepatitis C, while others do so only selectively. At times, a patient may find biopsy helpful in deciding about whether to pursue treatment. For example, some patients may choose to defer treatment if their biopsy is near normal but pursue treatment if their biopsy shows extensive liver disease. A liver biopsy also makes it possible to look for coinfection with hepatitis B or some other condition that might be causing abnormal liver enzymes.
The liver biopsy is the best way to judge the amount of damage that hepatitis C has caused. Elevated liver enzymes indicate inflammation, but they are insensitive; about one third of patients with significant inflammation found on liver biopsy will have normal liver enzymes.
PCR Tests
PCR tests for hepatitis C cause the viral DNA to replicate again and again until it can be detected from a blood sample. Supersensitive "qualitative" PCR tests, which can detect minute amounts of hepatitis C, are either positive or negative. "Quantitative" PCR tests are less sensitive but provide a sense of how much virus is present—the "viral load." Some 15 percent of people infected with hepatitis C clear the virus from their body without treatment. They may have a positive hepatitis C antibody test but negative PCR tests. These people do not require treatment. It is important to recognize that because hepatitis C has several strains, the presence of a hepatitis C antibody does not indicate immunity. If a person is found to have a positive PCR test, further testing to identify the strain of virus may be necessary in order to decide on the best course of treatment.
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