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Blood Tests for Hepatitis C

What Does My Blood Say About Hepatitis C?

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Updated June 10, 2014

Blood test
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Your blood might have a lot to say about hepatitis C. There are three general blood tests available for hepatitis C infections that doctors use to diagnose hepatitis C infection, determine the best course of treatment and monitor your progress. Considering that hepatitis C is a viral infection of the liver, which is tucked under your ribs just below your diaphragm, it's wonderful that doctors can find out so much information just by testing your blood.

All the tests described below must be requested by your doctor or provider and will start with a technician drawing blood, probably from your arm. Unfortunately, these test can't be completed in your doctor's office. The blood will be sent to a medical laboratory where technicians will process the blood according to the requested test and report the results back to the physician.

Hepatitis C Antibody

When hepatitis C viruses infect your liver cells (hepatocytes), your immune system responds by using special hepatitis C antibodies to mark the viruses as dangerous intruders. They won't attach to any other viruses or bacteria that might be in your body because they're only for hepatitis C viruses (other viruses or bacteria require different antibodies). Because antibodies are specific to a certain virus or bacterium, doctors can use the presence of the hepatitis C antibody (also called HCAb or anti-HCV) to tell if you've been infected with hepatitis C virus (HCV).

How Do Doctors Find Hepatitis C Antibodies in Your Blood?

Meet ELISA and RIBA. These are the names of two types of tests that detect antibodies in your blood. To determine if hepatitis C antibodies (HCAb or anti-HCV) are in your blood, doctors use a screening test called ELISA, which stands for Enzyme-Linked ImmunoSorbent Assay. There are many different ELISA tests, so doctors must use one specifically for hepatitis C. The ELISA test will search the blood sample for the hepatitis C antibody. If any are found, this means that you might have HCV infection.

The ELISA test is very sensitive and picks up approximately 95% of people who have antibodies as positive. However, it's so sensitive that sometimes it over-identifies antibodies in your blood as geared towards hepatitis C even sometimes when they're not. This degree of sensitivity has its advantages. For instance, when the ELISA test is negative, you can feel very confident that you are hepatitis C free. However, if the ELISA test is positive, there is a small possibility that the result could be incorrect. This is called a "false-positive" result. False-positives are most likely considered in people who lack the risk factors for hepatitis C.

When the ELISA test is weakly positive or when doctors think the test result doesn't match what they see clinically, a second test may be used to verify the original results. This test may be the RIBA test or another test, called HCV RNA, that directly measures the virus. The RIBA test (which stands for Recombinant ImmunoBlot Assay) uses a different approach to finding hepatitis C antibodies in your blood. If this test is positive, you probably have been infected with hepatitis C. It's important to realize that antibody tests usually can't distinguish between past or current infection. Doctors must use clinical information (such as medical history, signs and symptoms) or other tests to determine active or past infection.

Hepatitis C RNA

This powerful test allows doctors to see, among other things, how you are responding to treatment. It uses PCR technology (polymerase chain reaction) to detect the virus. While it's also used to establish current infection, it's mostly used to determine viral load. Your hepatitis C viral load is an estimate of how much HCV is in your blood. Since your viral load should decrease after a successful course of treatment, by monitoring the levels of HCV in your blood, doctors can accurately determine how you're responding to the treatment. If your viral load doesn't decrease, they may need to change your therapy.

In summary:

  • Negative ELISA = No hepatitis C antibodies found in blood. You are probably not infected with HCV.
  • Positive ELISA = You may have HCV infection. However, it's possible this is a false-positive. More testing is required.
  • Negative RIBA = No hepatitis C antibodies found in blood. You are probably not infected with HCV.
  • Positive RIBA = Hepatitis C antibodies were found in your blood using a very sophisticated lab test. You probably have been infected with hepatitis C.
  • Negative HCV RNA = No active HCV infection.
  • Positive HCV RNA = Active HCV infection.

Hepatitis C Virus Genotyping

Hepatitis C viruses are not all the same. Certainly, they are all identified as hepatitis C viruses and they all can cause acute and chronic hepatitis C, but they're not exactly genetically alike. They have slightly different variations in their genes and are grouped by these variations into different genotypes. Genotypes are important because hepatitis C viruses with certain genetic variations are harder to treat successfully and usually require a different treatment approach. Other hepatitis C viruses are much easier to treat because they respond well to shorter treatment schedules. Doctors determine your HCV genotype by using a laboratory test called RT-PCR, which stands for reverse transcription polymerase chain reaction. This test analyzes the genetic material of the virus to determine its sequence. Based on its sequence, technicians can determine the virus' genotype. All blood testing requires a certain level of training and equipment, but RT-PCR requires relatively more. Because of this, it's an expensive test (it usually costs more than $100 to perform). However, it's worth the cost. Knowing your genotype can significantly reduce the duration of your treatment.

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  1. About.com
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  3. Hepatitis
  4. Diagnosis
  5. Blood Tests for Hepatitis C Viral Infection

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