Liver Function and Other Diagnostic Tests for Hepatitis C

A number of blood tests are used to diagnose hepatitis C. Certain blood test results indicate only that the person is infected, while others indicate the amount of hepatitis C virus in the body. Not all blood test results are 100 percent reliable: one can test negative for the virus and still be infected. For that reason, more than one analysis is usually performed. If you've been exposed to situations in which HCV can be transmitted, you should be tested.

Liver function tests evaluate the level of liver enzymes in the bloodstream. If the count is high, the possibility of hepatitis C infection or another liver disorder increases. Generally, if the count is low, the organ is functioning properly.

Liver function tests do not specifically check for the presence of hepatitis C; they evaluate only liver enzyme levels. Based on the results, your doctor may order more specific testing. If you've been diagnosed with chronic HCV, regular liver enzyme assessments are a way for your doctor to assess inflammation.

The first blood test you're likely to have is an anti-HCV test. This looks for the presence of specific antibodies the immune system manufactures in response to the hepatitis C virus.

A positive result may indicate a previous infection, with no current virus, or it can indicate an ongoing infection. A negative result doesn't rule out the possibility of HCV. It only indicates that the test did not detect HCV antibodies. Antibodies build up to detectable levels only after weeks of infection.

Regardless of the result of the anti-HCV evaluation, a second test called a HCV RNA test will probably be performed. This confirms or refutes the initial result. Neither test can ascertain whether the infection is acute or chronic, or whether the virus is still active or has run its course.

A quantitative polymerase chain reaction test (PCR) measures the amount of HCV particles in the bloodstream. The PCR test can establish whether the virus is still active and indicate how virulent the infection is. The results of polymerase chain reaction allow the doctor to determine how long a treatment program should be. PCR tests are sometimes used to monitor a patient's response to therapy as treatment progresses.

Hepatitis C virus has six different major strains, with several additional sub-types. Knowing which strain is causing the infection helps doctors determine how well the infection is responding to treatment. For this reason, your blood may undergo viral genotyping to determine the strain of HCV.

Chronic HCV can cause cirrhosis of the liver. Inflammation damages healthy tissue, which is replaced with scar tissue. Your doctor may perform a liver biopsy to assess the damage. A needle is inserted into the liver and a tiny sample of tissue is removed. This tissue is then examined for signs of inflammation and scarring.

Resources

Centers for Disease Control and Prevention (CDC). (reviewed 2005). Frequently asked questions: Diagnosis and testing.

Lab Tests Online. (updated 2005). Hepatitis C virus.

National Hepatitis C Program. (reviewed 2002). Laboratory tests and hepatitis C.

National Institute of Allergy and Infectious Diseases. (updated 2001). What you should know about hepatitis C.

Smith, R. (1999). A painful connection: HCV, cryo and neuropathy. Hepatitis Central.

Thomas, C. L, ed. (1997). Taber's Cyclopedic Medical Dictionary 18th ed. Philadelphia: F.A. Davis Co.