Hepatitis C

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Hepatitis C UpdateLaboratory Issues

• Hema Kapoor MD. SM
• Virology Section Manager
• Bureau of Laboratories
• Michigan Department of Community Health

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Laboratory Tests for HCV

• Available at MDCH
• Screening tests
• EIA
• Supplemental
• RIBA ( Recombinant immunoblot assay)
• Nucleic acid Amplification tests

• Additional Tests Available Commercially
• CIA (Chemiluminescence's immunoassays)
• Quantitative RNA Tests
• Genotyping
• Core Protein Antigen

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Laboratory Algorithm for HCV Testing
HCV EIA 2.0 ( Abbott), HCV version 3.0 ELISA(
Ortho), VITROS Anti-HCV
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Anti-HCV EIA False Positivity by Population
Prevalence
100
HCWs Military STD Clients Pregnant Women
50
Percent False Positive
Dialysis Transfused
Injecting Drug Users
NANB Hepatitis ALT
0
lt5 10 60 gt90
Prevalence of HCV Infection
As judged by RIBA or NAT
Source CDC
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CDC
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Consistency of Reported Anti-HCV Results

• Screening test positive signal to cutoff ratios
• Results above the cutoff should predict a true
  antibody positive
• Only results below the cutoff would require
  supplemental antibody testing
• Cutoff should perform the same regardless of the
  population being tested

Not intended for use in screening donors as
provided by FDA guidance
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Anti-HCV Test Versions Evaluated

• Ortho 3.0, RIBA 3.0
• N25,532
• High-risk
• Hemodialysis patients
• STD patients
• HCWs
• General population (NHANES IV)
• VITROS Anti-HCV (Ortho), RIBA 3.0
• N1326
• Clinical specimens (Hospital-based patients)
• Low prevalence populations

• Abbott 2.0, RIBA 3.0 N8,754
• STD patients
• Students

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EIA Signal to Cutoff Ratio

• Signal Optical density (OD) value of the sample
  being tested.
• Cut off Mean absorbance of negative Control
  plus 0.600.

Example Sample OD Cutoff OD S/CO 1.595 0.623
2.56 1.243 0.543 2.29 1.271 0.543 2.34

s/cut off (s/co)- ?3.8
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Proportion of Anti-HCV EIA Screening Test
Positive Results Testing RIBA Positive by
Average S/Co Ratio
Prevalence
4.3
2.2
0
EIA 2.0 or EIA 3.0
Source CDC. MMWR 200352 (No. RR-3).
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Proportion of Anti-HCV CIA Screening Test
Positive Results Testing RIBA Positive by S/Co
Ratio
Prevalence
VITROS Anti-HCV assay
Source CDC. MMWR 200352 (No. RR-3).
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Proportion of Anti-HCV EIA RR Results Requiring
RIBA Based on S/CO Ratio lt3.8and HCV Prevalence
Source CDC. MMWR 200352 (No. RR-3).
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Use of EIA/CIA S/CO Ratio to Determine Need for
Additional Routine Testing

• Screening-test-positive samples with s/co ratios
  gt3.8/8 can be reported based on screening test
• gt95 will be RIBA positive.
• Screening-test-positive samples with s/co
  lt3.8/8 require additional testing because most
  are falsely positive.
• In high prevalence populations few in this range.
• Limits cost while improving accuracy of reported
  results.

Applies only to Ortho 3.0 or Abbott 2.0 EIA
Applies only to Ortho Vitros CIA
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Laboratory Algorithm for Anti-HCV Testing and
Result Reporting MMWR 2003
HCV EIA 2.0( Abbott), HCV version 3.0 ELISA
(Ortho), VITROS Anti-HCV
Source CDC. MMWR 200352 (No. RR-3).
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Repeatedly Reactive Anti HCV

• Supplementary serological confirmation testing
  was not performed on this specimen with a high
  serum to cut-off ration in accordance with CDC
  guidelines (MMWR, 52 RR03 1-16). Appx 95 of
  specimens with a high serum to cut-off ratio
  confirm positive when tested in supplementary
  tests. The serum to cutoff ratio is not related
  to severity of disease or acute/chronic phase of
  infection. Supplementary testing is available
  only after consultation with Dr. Jeff Massey

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Advantages and Impact ?
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Advantages of Revised Laboratory Guidelines

• Standard reporting of anti-HCV positive results.
• Reliable Interpretation of anti-HCV results.
• Ensure positive patients receive follow-up
• Prevent unnecessary evaluation of
  false-positives
• Low cost of additional testing
• Better understanding of performance and
  interpretation

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Implications

• Patients and physicians can reliably interpret
  results
• Further clinical evaluation limited to true
  positives
• Limit psychological stress on patients who test
  falsely positive
• Substantially improve ability to establish public
  health surveillance systems to monitor effect of
  prevention and intervention activities