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Reading a Lab Report: A Basic Primer
Monitoring hepatitis C (HCV) treatment and managing HCV disease is a complex process that includes using blood tests. These include a complete blood count (CBC), chemistry panel, and liver function tests. This fact sheet is intended to help you understand these kinds of blood tests, and is not intended as medical advice. All people with HCV should consult a medical provider for diagnosis and treatment of HCV.
An Overview of HCV Diagnostic Tests
A variety of different tests are used to diagnose hepatitis C. These include:
• HCV Antibody Test
• HCV Viral Load Test or HCV RNA Test
• HCV Genotype/Subtype Test
• Liver Biopsy
• Non-Invasive Tests
• Staging Liver Disease
Here are more fact sheets that provide more detailed information about diagnostic tests:
In 2013 the Food and Drug Administration (FDA) cleared Fibroscan for marketing. Fibroscan is based on ultrasound elastography technology using a machine that sends a vibration wave through the liver. The Fibroscan will measure how long it takes for the wave to travel through the liver. It has been tested extensively in people with hepatitis C.
Use of FibroScan® in Clinical Practice
The FibroScan® is a non-invasive modality which measures fibrosis of the liver by assessing parenchymal (tissue) stiffness. It has been evaluated in more than 400 peer-reviewed articles in most types of liver disease [1-12]. In April 2013, the Food and Drug Administration approved its use in the U.S., stating “FibroScan® is indicated for the measurement of shear wave speed in the liver. The shear wave speed may be used as an aid to clinical management of patients with liver disease.”
HCV Viral Load Tests
Viral load tests are blood tests that measure HCV ribonucleic acid (RNA, or genetic material) in the blood. The presence of viral RNA indicates that the virus is actively replicating (reproducing and infecting new cells). A viral load test is usually first done after a person has tested positive for exposure to HCV based on an antibody test. A blood sample is taken and the amount of HCV RNA in a milliliter of blood is measured. Viral load tests confirm whether an individual is actively infected with HCV. Viral load test results are reported in terms of International Units per milliliter (IU/mL).
HCV Genotype, Quasispecies & Subtype
The term genotype refers to different genetic variations or strains of hepatitis C (HCV). The variance in genetic differences is approximately 1/3 between the different genotypes. There are seven major groups or genotypes numbered 1 to 7 although some experts believe that there may be as many as 11. Within each genotype are further divisions called subtypes (for example 1a and 1b) and mutations of the hepatitis C virus called quasispecies.
When a person is infected with the hepatitis C virus (HCV), the immune system produces antibodies against the virus. It usually takes the immune system a few weeks to develop enough antibodies to be detected by an antibody test. A person who has been recently infected with HCV may be in the window period – the time it takes between initial infection and the development of antibodies. The average time it takes for people to develop HCV antibodies is 2 months, but can take as long as 6 months; however, this is uncommon.