Master slide

1
Guidelines for Laboratory Testing and Result
Reporting for Antibody to Hepatitis C Virus
Wendi L. Kuhnert, Ph.D. Division of Viral
Hepatitis Centers for Disease Control and
Prevention
2
Guidelines Development

• Working group
• Federal agencies
• CDC, FDA (CDRH, CBER)
• Professional associations
• APHL
• ASCP
• CAP
• NACB
• AACC
• ACLA
• Other experts
• University and VA hospital laboratories

• Other collaborators
• Blood collection establishments
• Manufacturers

3
These Guidelines Are NOT Intended

• For screening or notification of blood, plasma or
  other donors, as provided for under FDA guidance
  or regulations
• To change manufacturers labeling for performing a
  specific test
• To dictate medical practice, i.e., what tests
  physicians are able to order

4
Testing for Anti-HCV

• Recommended for initially identifying persons
  with HCV infection
• Antibody screening assay followed by more
  specific assay for screening-test-positives
• As is done for HBsAg and anti-HIV
• Verifying presence of anti-HCV
• Minimizes unnecessary medical visits and
  psychological harm for persons who test falsely
  positive
• Ensures counseling, medical referral and
  evaluation targeted for persons serologically
  confirmed as having been HCV infected

5
Reasons for HCV Testing

• Diagnosis in the clinical setting
• Acute and chronic disease
• Asymptomatic infection
• Screening programs in non-clinical settings
• High-risk (e.g., injection drug users,
  hemophilia)
• Low-risk (e.g., firefighters)
• Worried well
• Public health surveillance
• Monitor incidence and prevalence to target and
  evaluate prevention efforts
• Research

6
Exposures Known to be Associated with HCV
Infection in the United States

• Injecting drug use
• Transfusion, transplant from infected donor
• Therapeutic (contaminated equipment, unsafe
  injections)
• Hemodialysis
• Occupational exposure to blood
• Mostly needle sticks
• Birth to HCV-infected mother
• Sex with infected partner
• Multiple sex partners

7
Performance of Screening Tests

• Positive Predictive Value (PPV)
• Probability that a person with a positive test is
  a true positive
• Varies depending on prevalence of infection in
  population being screened

8
How Anti-HCV Test Results Are Used

• Clinical diagnosis of etiology of liver disease
• Postexposure management
• Screening asymptomatic persons
• Most being tested for the first time
• Risk for infection highly variable
• High-risk (e.g., injection drug users)
• Low-risk (e.g., health-care workers)
• Lower-risk (e.g., worried well)
• Public health surveillance
• Monitor incidence and prevalence to target and
  evaluate prevention efforts

9
Testing Practices

• In 1998, CDC published recommendations that all
  screening-test positives undergo more specific
  testing
• Broad educational programs targeted to physicians
  and other health care providers
• Little impact on test ordering practices
• Substantial variation among laboratories in
  routine testing algorithms
• Many report screening test positive results only
• Those that confirm use different methods (RIBA,
  NAT)
• Without additional information, may not be able
  to determine true antibody or HCV infection
  status

10
Purpose of Laboratory Guidelines

• Adoption of standard algorithm by all
  laboratories that perform in vitro diagnostic
  testing
• Ensure results reflect true antibody status
• Independent of clinical information or origin of
  sample
• Educate
• Importance of more specific testing
• Accurate interpretation of screening and
  supplemental results
• When more specific testing should be performed
• Which tests to use
• Eliminate cost as barrier to more specific
  testing

Not intended for screening or notification of
donors
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Options for More Specific Testing When Anti-HCV
Test Requested

• Perform more specific testing on all
  screening-test positives or
• Use screening test positive signal to cutoff
  ratios to determine need for more specific
  testing
• Cutoff performs the same regardless of the
  population being tested

12
Evaluation of Anti-HCV S/Co Ratios

• Screening tests
• Ortho 3.0 enzyme immunoassay (EIA) (n25,532)
• Abbott 2.0 EIA (N8,754)
• Ortho VITROS enhanced chemiluminescent assay
  (CIA) (n1326)
• Abbott AxSYM anti-HCV (MEIA) (N415)
• More specific testing of screening-test positives
• RIBA 3.0
• NAT (Amplicor, Procleix, Nested RT-PCR)

13
Routine Testing for HCV Infection

• Anti-HCV indicates past or present infection
• Does not distinguish acute, chronic, or resolved
• Screening Assay
• Repeat reactive for EIA positive
• Single reactive for CIA and MEIA positive
• Sensitivity gt97 specificity 99
• 30-50 EIA repeat reactives falsely positive if
  used alone in low prevalence (lt10) populations

14
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
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Presence of a Risk FactorDoes Not Necessarily
Equate withIncreased Risk
16
Interpretation of HCV Test Results
Screening RIBA for NAT for Anti-HCV HCV
Infection Test Anti-HCV HCV RNA Status Status
Not done Not done Unknown Unknown
- NA - None
Not done Past/current
/ not done Current
17
Anti-HCV Testing Practices of State and
Territorial Public Health and VA Medical Center
Laboratories, 2002
Public health VAMC Testing
Practices laboratories laboratories Tests
offered n43 n67 Screening
test 65 100 RIBA 38
21 Qualitative NAT 29 75 Quantitative
NAT 13 98 Supplemental testing
performed n29 n67 All screening-test-positiv
e results 35 22 Low-positive
screening-test results 10 3 Only by
physician request 17 75 None
offered 38 0

• Signal to cutoff ratio below a specified value
• Source CDC. MMWR 200352 (No. RR-3).

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These Guidelines Are NOT Intended

• For screening or notification of blood, plasma or
  other donors, as provided for under FDA guidance
  or regulations
• To change manufacturers labeling for performing a
  specific test
• To dictate medical practice, i.e., what tests
  physicians are able to order

19
Anti-HCV Test Versions Evaluated
EIA Format Assays

• 1. Ortho 3.0, RIBA 3.0 - N25,532
• High-risk
• Hemodialysis patients
• STD patients
• HCWs
• General population (NHANES IV)

• 2. Abbott 2.0, RIBA 3.0 - N8,754
• Students
• STD patients

20
Anti-HCV Test Versions Evaluated cont.
CIA Format Assay

• VITROS Anti-HCV (Ortho), RIBA 3.0 - N1326

• Clinical specimens (Hospital-based patients)
• Low prevalence populations

MEIA Format Assay
1. Abbott AxSYM anti-HCV, RIBA 3.0 - N 415

• High-risk
• Hemodialysis patients
• Reference laboratory specimens
• Clinical specimens (Hospital-based patients
• General Population (NHANES IV)

21
Sample Size

• Although the sample sizes of these two groups
  were smaller than those used for our original
  evaluation of other FDA-approved assays, the 95
  confidence intervals surrounding the point
  estimates were similar.

22
Improving Reliability and Consistency of Reported
Anti-HCV Results

• Can screening test positive signal to cutoff
  ratios be routinely used by laboratories to
  determine need for supplemental antibody testing
• 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
23
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).
24
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).
25
Proportion of Anti-HCV MEIA Screening Test
Positive Results Testing RIBA Positive by S/CO
Ratio
Prevalence
Percent RIBA Positive

(n 334)
(n 81)
Screening-test-positive s/co ratio
Abbott AxSYM anti-HCV
26
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).
27
Use of EIA/CIA/MEIA S/CO Ratio to Determine Need
for Additional Routine Testing

• Screening-test-positive samples with S/CO ratios
  gt3.8/8/10 can be reported based on screening
  test
• gt95 will be RIBA positive
• Screening-test-positive samples with S/CO
  lt3.8/8/10 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
Source CDC. MMWR 200352 (No. RR-3).
Applies only to Ortho Vitros CIA Applies only
to Abbott AxSYM MEIA
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Laboratory Algorithm for Anti-HCV Testing

• Perform supplemental testing on all specimens
  with screening test positive results Or
• Perform supplemental testing based on screening
  test positive signal to cutoff ratios
• Samples with high s/co ratios can be reported
  based on screening test results alone (gt95 will
  be RIBA positive)
• Only samples with low s/co ratios require
  additional testing because most are falsely
  positive
• In high prevalence populations few in this range
• Limits cost while improving accuracy of reported
  results

Not intended for donor screening
Source CDC. MMWR 200352 (No. RR-3).
29
Laboratory Algorithm for Anti-HCV Testing and
Result Reporting MMWR 2003
REPORT
Negatives
Screening Test for Anti-HCV
OR
All positives
Positives defined by s/co ratios
Positives with low s/co ratios
Positives with high s/co ratios
OR
REPORT
RIBA for anti-HCV
Nucleic acid test for HCV RNA
Negative
Positive
REPORT
Positive
Negative
Indeterminate
RIBA for anti-HCV
REPORT
REPORT
REPORT
Positive
Indeterminate
Negative
REPORT
REPORT
REPORT
HCV EIA 2.0, HCV version 3.0 ELISA, VITROS
Anti-HCV
Source CDC. MMWR 200352 (No. RR-3).
30
Questions/Publications
Does a laboratory have the freedom to choose a
different s/co ratio for their use?

• Oethinger et al. found No evidence of HCV
  infection in any samples with a s/co ratio of
  5. Therefore a borderline category of samples
  with a s/co ratio of between 1 and 5 was created.
• The CDC guidelines were intended to provide a
  cost-savings measure for laboratories performing
  HCV testing. Other cut-offs can be validated by
  laboratories based on their own patient
  population and requirements.

• Oethinger et al. 2005. Efficiency of the Ortho
  VITROS Assay for Detection of Hepatitis C
  Virus-Specific Antibodies Increased by
  Elimination of Supplemental Testing of Samples
  with Very Low Sample-to-Cutoff Ratios. J Clin
  Micro 43(5) 2477-80.

31
Questions/Publications
What are the compliance issues surrounding
inclusion of reflex testing in a test requisition?

• A. Paxton reported that some laboratories wont
  perform reflex testing in certain circumstances
  as the CDC guidelines as because of compliance
  implications.
• Guidelines state that the laboratory requisition
  should be modified to state the circumstances
  under which reflex setting will be performed
  this provides adequate documentation for CMS.
• Education is key to this step physicians should
  be educated by their laboratories as to the
  benefits of this result.

Paxton, A. 2005. HCV testing swaps high-low for
yes-no. CAP Today. April.
32
Questions/Publications
Why dont the recommendations include subsequent
testing for samples with a high s/co ratio?

• The question of whether a patient is chronically
  infected or has resolved their infection is an
  important one and additional testing (NAT) for
  samples with a high s/co ratio would help to
  resolve this.
• The goal of the MMWR was to provide guidelines
  for reporting out results for anti-HCV.
  Additional or altered algorithms as addressed
  earlier are acceptable and should be considered
  based on the laboratory and patient population.
• To recommend PCR for all laboratories would not
  be cost effective or reasonable given sampling
  conditions. In addition, the recommendations
  state that further evaluation of the patient is
  warranted after a positive anti-HCV result.

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Advantages

• Algorithm for testing same in all settings
• Standardizes interpretation of reported results
  
• Independent of clinical information or origin of
  sample
• Cost increase relatively minimal
• Does not preclude additional testing as part of
  clinical evaluation or management

34
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