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Hepatitis C –Update Laboratory Issues PowerPoint PPT Presentation


Hepatitis C –Update Laboratory Issues. Hema Kapoor MD. SM Virology Section Manager Bureau of Laboratories Michigan Department of Community Health. Available at MDCH Screening tests EIA Supplemental RIBA ( Recombinant immunoblot assay) Nucleic acid Amplification tests.

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Hepatitis C –Update Laboratory Issues

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Hepatitis c update laboratory issues l.jpg

Hepatitis C –UpdateLaboratory Issues

Hema Kapoor MD. SM

Virology Section Manager

Bureau of Laboratories

Michigan Department of Community Health


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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

Laboratory Tests for HCV


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REPORT

Negatives

Screening Test for Anti-HCV*

Positive EIA/CIA Test

RIBA for anti-HCV

OR

Nucleic acid test for HCV RNA

Negative

Positive

REPORT

Positive

Negative

Indeterminate

RIBA for anti-HCV

REPORT

REPORT

REPORT

Negative

Indeterminate

Positive

REPORT

REPORT

REPORT

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

<5%10%60% >90%

Prevalence of HCV Infection

Source: CDC

* As judged by RIBA or NAT


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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

N=25,532

  • High-risk

  • Hemodialysis patients

  • STD patients

  • HCWs

  • General population (NHANES IV)

    VITROS Anti-HCV (Ortho), RIBA 3.0

    N=1326

  • Clinical specimens (Hospital-based patients)

  • Low prevalence populations

Abbott 2.0, RIBA 3.0N=8,754

  • 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 ODCutoff ODS/CO

1.5950.6232.56

1.2430.5432.29

1.2710.5432.34

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 2003;52 (No. RR-3).


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>

(n = 1184)

(n = 142)

Screening-test-positive s/co ratio

Proportion of Anti-HCV CIA* Screening Test Positive Results Testing RIBA Positive by S/Co Ratio

Prevalence

* VITROS Anti-HCV assay

Source: CDC. MMWR 2003;52 (No. RR-3).


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Proportion of Anti-HCV EIA RR Results Requiring RIBA Based on S/CO Ratio <3.8and HCV Prevalence

Source: CDC. MMWR 2003;52 (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 >3.8*/8† can be reported based on screening test

    • >95% will be RIBA positive.

  • Screening-test-positive samples with s/co <3.8*/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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    REPORT

    Negatives

    Screening Test for Anti-HCV

    OR

    Positives defined by s/coratios*

    All positives

    Positives with highs/co ratios

    Positives with low s/co ratios

    OR

    REPORT

    RIBA for anti-HCV

    Nucleic acid test for HCV RNA

    Negative

    Positive

    REPORT

    Negative

    Positive

    Indeterminate

    RIBA for anti-HCV

    REPORT

    REPORT

    REPORT

    Positive

    Negative

    Indeterminate

    REPORT

    REPORT

    REPORT

    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 2003;52 (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


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