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Hepatitis C: An Overview

Prevalence | Incidence | Demographics | Natural History | Transmission
Prevention | HCV Testing | Treatment | What You Need To Know

HCV Testing

Who should be tested?

  • Testing Routinely Recommended Based on Risk of Infection
  • Person who ever injected illegal drugs
  • Persons with selected medical conditions
    • Persons who received clotting factor concentrates produced before 1987
    • Persons who were ever on long-term hemodialysis
    • Persons with persistently abnormal alanine aminotransferace levels (persons with chronic liver disease)
  • Testing Routinely Recommended Based on Risk of Infection
  • Prior recipients of transfusions or solid organs
    • Persons who were notified that they received blood from a donor who later tested positive for HCV infection
    • Persons who received a transfusion of blood or blood components before July 1992
    • Persons who received an organ transplant before July 1992
  • Testing Routinely Recommended Based on Need for Exposure
    • Health care, emergency medical, and public safety workers after needlesticks, sharps, or mucosal exposures to HCV positive blood
    • Children born to HCV positive women

What do test results mean?

  • Initial Screening
    • Used to determine exposure/detect hepatitis C antibodies.
    • Example: Enzyme immunoassays (EIA)
    • It takes an average of 6 to 8 weeks before antibodies can be detected.
    • Within three months of infection, 97 percent of persons will have sufficient antibodies to be detected with a screening test.
  • Initial Screening – Negative Result
    • A negative test most likely means that a person is not infected.
    • False negatives are uncommon.
      • May occur if a person has been recently infected.
      • May occur in individuals who are immuno-suppressed or on long-term hemodialysis.
  • Initial Screening - Positive Result
    • False positives are uncommon.
      • Most likely to occur in individuals at low-risk for infection.
      • May occur in individuals with autoimmune liver disease.
    • A positive test, especially in a person with known risk factors, most likely means that they have been exposed to the virus.
    • Screening test results can be verified with a supplemental or confirmatory test.
  • Confirmatory Testing
    • To ensure that a positive screening test result is a true positive.
    • To distinguish between a resolved and an active infection.
    • They can be used alone or more than one test can be used.
  • Supplemental Confirmatory Assay
    • Detects antibodies to HCV.
    • Recombinant immunoblot assay (RIBA)
    • Can be done on the same blood sample as the screening assay.
    • Used to determine whether an antibody positive result is a true positive result, especially in low prevalence populations.
  • Virus Detection Tests
    • Nucleic Acid Tests (NATs)
    • Tests that determine presence of the hepatitis C virus in the blood through detection of HCV RNA.
    • Detection of HCV RNA provides definitive proof that an infection exists.
    • There are both qualitative and quantitative virus detection tests.
  • Qualitative Virus Detection Tests
    • Can detect the virus as early as one or two weeks after exposure.
    • Can detect the virus at lower levels than quantitative tests.
    • Are the preferred test for determining active infection. (AMA guidelines)
    • Examples: Reverse Transcriptase-polymerase chain reaction assays (RT-PCR) or Transcription mediated amplification (TMA)
  • Quantitative Virus Detection Tests
    • Can quantify the actual amount of the virus or the viral load.
    • Often used to monitor response to treatment.
    • Examples: Reverse Transcriptase-polymerase chain reaction assays (RT-PCR), Transcription mediated amplification (TMA), or branched chain DNA assays
  • AMA: Testing Asymptomatic People Flowchart
  • S/Co Ratios
    • The CDC guidelines allow for the use of screening-test-positive signal-to-cut off ratios (s/co ratios) to determine need for supplemental testing.
    • Positive screening tests with high s/co ratios have been demonstrated to predict a supplemental serologic-test-positive 95 percent or greater of the time.
    • These tests can be reported as HCV-antibody positive without supplemental testing.
  • S/Co-Ratios - MDCH Flowchart

If a person is chronically infected what other tests will they do?

  • Genotyping
    • There are at least six different genotypes of HCV.
      • Genotype 1 - 70 to 75 percent of persons infected in the US.
      • Genotypes 2 and 3 – 10 to 15 percent of persons infected in the US.
    • Genotype testing should be done on all HCV positive people considering treatment.
      • Often determines length of treatment.
      • Is also a predictor of response to treatment.
  • Liver Enzyme Tests
    • Elevated ALT levels are an indirect measure of liver cell inflammation and damage.
    • In patients with risk factors and elevated liver enzymes, HCV infection is probable.
    • However, the absence of elevation does not rule out significant liver damage.
    • One-third to one-half of HCV infected individuals will have a normal ALT level.
  • Liver Biopsy
    • Most sensitive measure of disease severity.
    • Used to determine stage of fibrosis.
    • Can be used to help predict natural history of disease.
    • Often used to determine the need for treatment.
    • Can also be used to predict response to treatment.
    • May not be indicted for patients with genotypes 2/3.
  • Quantitative Virus Detection Tests
    • Genotype 1:
      • A change in viral level is used to monitor response to hepatitis C treatment.
      • Test before treatment starts
      • Test at 12 weeks

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