Guidelines for Laboratory Testing and Result Reporting for Antibody to Hepatitis C Virus Miriam J. Alter, Ph.D. Division of Viral Hepatitis Centers for Disease Control and Prevention BPAC September 18, 2003

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 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

6 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

7 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

8 Anti-HCV Testing Practices of State and Territorial Public Health and VA Medical Center Laboratories, 2002 Tests offered n=43n=67 Screening test65%100% RIBA38% 21% Qualitative NAT29% 75% Quantitative NAT13% 98% Supplemental testing performedn=29n=67 All screening-test-positive results35% 22% Low-positive screening-test results*10% 3% Only by physician request17% 75% None offered38% 0% * Signal to cut-off ratio below a specified value Source: Werner B, APHL, 2002; Dufour R, VA, 2002 Testing Practices Public health VAMC

9 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

10 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

11 Evaluation of Anti-HCV S/CO Ratios Screening tests –Ortho 3.0 enzyme immunoassay (EIA) (n=25,532) –Abbott 2.0 EIA (N=8,754) –Ortho VITROS enhanced chemiluminescent assay (CIA) (n=1326) More specific testing of screening-test positives –RIBA 3.0 –NAT (Amplicor, Procleix, Nested RT-PCR)

Study Groups for Evaluating EIA and CIA S/Co Ratios by Prevalence of HCV Infection 1187* * Number tested >

Proportion of Anti-HCV RR EIA Results Testing RIBA Positive by S/CO Ratio Source: MMWR 2003;52(No. RR-3):1-15. (N=231) (N=18)(N=21) (N=765) EIA S/CO Ratio _ 13

Proportion of Anti-HCV EIA* Screening-Test Positives Testing RIBA or NAT Positive by Average S/Co Ratio Source: MMWR 2003;52(No. RR-3):1-15. * EIA 2.0 or EIA 3.0 _ Group prevalence2%10%25% RIBA positive NAT positive 14

Proportion of Anti-HCV CIA* Screening Test Positives Testing RIBA Positive by S/Co Ratio Source: MMWR 2003;52(No. RR-3):1-15 * VITROS Anti-HCV assay Prevalence > 15

Proportion of Anti-HCV Screening Test Positives Requiring RIBA Based on Low S/Co Ratios by HCV Prevalence Source: MMWR 2003;52(No. RR-3):

17 Using Screening Test Positive S/Co Ratio to Determine Need For Additional Testing* Positives with high s/co ratios can be reported based on screening test results alone –>95% will be RIBA positive Only positives with low s/co ratios require additional testing (most falsely positive) –<20% will confirm positive Limits cost while improving accuracy of reported results –<5% of high risk persons require additional testing *Applies only to HCV EIA 2.0, HCV version 3.0 ELISA, and VITROS Anti-HCV

18 Implementation Determine reflex testing option to be used Revise SOP –Algorithm chosen –Procedure for reporting results –Provide interpretation of results with report Educate staff and customers Modify requisition form

19 Implications Patients and physicians can reliably interpret results –Further clinical evaluation limited to true positives –Limit unnecessary medical visits and 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

21 Interpretation of HCV Test Results Screening RIBA for NAT forAnti-HCVHCV Infection Test Anti-HCVHCV RNAStatusStatus - NA*NA-None * Not applicable +-NA-None ++Not done+Past/current ++/not done ++Current +Not done-UnknownUnknown † † Single negative HCV RNA result cannot determine infection status ++-+Past/current § § HCV RNA can be intermittent; repeat HCV RNA +Not doneNot doneUnknownUnknown