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Influenza Surveillance Viral Isolation Laboratory TX DSHS July 23, 2008

Explore the various laboratory diagnostic testing methods for influenza, such as viral isolation, rapid EIA kits, real-time RT-PCR, and more. Learn about their advantages, limitations, and implications for patient management.

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Influenza Surveillance Viral Isolation Laboratory TX DSHS July 23, 2008

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  1. Martha Thompson, MPHViral Isolation Team LeaderMedical Virology GroupLaboratory Services SectionTX DSHS Influenza Surveillance Viral Isolation Laboratory TX DSHSJuly 23, 2008

  2. Viral Isolation • 2007-2008 Season • Laboratory Diagnostics: Influenza • Influenza testing: Viral Isolation Lab • Cell Culture • Immunofluorescence • Hemagglutination/HA Inhibition • Levels of Identification • Specimen rejection criteria • Summary of isolates sent to CDC

  3. Influenza A specimens not subtyped (2) • B strains identified as B/Shanghai/361/2002-like (B/Yamagata) by the viral isolation laboratory

  4. Laboratory Diagnostic Testing: Influenza

  5. Rapid EIA Kits • Advantages • Rapid and on-site testing • Impact patient management • Simple • CLIA waved

  6. Limitations • Typing/Results • Flu + only • A or B • No subtyping • Variation between kits • Storage conditions • Acceptable specimens (includes type and time of collection) • Must follow manufacturer instructions • Less sensitive than viral culture or molecular • False negatives • PPV and prevalence in the community affect test performance

  7. These limitations affect test performance • Patient management • Use positive and negative predictive values to assess test performance • PPV: Probability of disease in a patient with a positive test result • PNV: Probability of no disease in a patient with a negative test result

  8. Test Performance Disease Test Result Sensitivity = TP/TP+FN Specificity = TN/TN+FP PPV= TP/TP+FP PVN = TN/TN+FN

  9. Positive predictive value: Prevalence=20% Disease Test Result Predictive Value Positive = TP/TP + FP = 380/380+64 = 85.6%

  10. Positive predictive value: Prevalence = 1% Disease Test Result Predictive Value Positive= TP/TP + FP = 19/19+80 = 19.1%

  11. Conclusion • When prevalence is low, the PPV is low and chance of getting a false positive increases • Confirm with culture during off season

  12. Other Methods • DFA • Quick TAT • No culture available for further studies • Serology • Positive results can be obtained even after viral shedding has stopped • Acute/convelescent serum required—delay in diagnosis • No culture available for further studies

  13. Advantages Rapid: Sensitive/Specific* High throughput can be obtained Identification of highly pathogenic strains of avian influenza possible Disadvantages Costly Risk of cross contamination Variability among protocols means variability among sensitivity/specificity rates No isolate available for further studies Real Time RT-PCR

  14. Cell Culture • Confirm virus is infectious • Antigenic characterization • Vaccine Studies • Antiviral resistance testing • Important for surveillance • Slower TAT • 2-10 days

  15. Immunofluorescence (IFA) • Indirect test • Antibody to Flu A and B antigens • Fluorescent tag • A, B, or Neg • If positive – continue with subtyping • Reagents in WHO kit

  16. Hemagglutination/HA Inhibition • Antisera to neutralize antigens • Blood as an indicator, agglutinates to antigen • Antigenic characterization

  17. Antisera Level of identification A(H3) A(H1) B/Shanghai/361/2002-like B/Malaysia/2506/2004-like Isolates to CDC Beginning, middle, and late season Patients who received vaccine Anything unusual Unable to subtype 2007-2008 WHO Influenza Reagent Kit

  18. WHO Summary: Weeks Ending Oct 6, 2008 – May 17, 2008

  19. Vaccine Strains • 2007-2008 Vaccine Strains • A/Solomon Islands/3/2006 (H1N1)-like • A/Wisconsin/67/2005 (H3N2)-like • B/Malaysia/2506/2004-like (B/Victoria) • A/Brisbane/10/2007 is a variant form of A/Wisconsin/67/2005 strain • All B strains identified by VI lab were B/Shanghai/361/2002-like (B/Yamagata)

  20. Specimen Rejection Criteria • Meet regulatory standards • Optimal specimen for testing • Expired transport media • Wooden sticks/Calcium alginate • Inhibitors to virus: preservatives • Cotton swabs • First AND Last name: on specimen AND submission form • 1 Specimen = 1 Submission form • DATE of COLLECTION

  21. Contact Information martha.thompson@dshs.state.tx.us Phone 512-458-7594 Fax 512-458-7293 Viral Isolation Laboratory 512-458-7111 x2452

  22. Useful Links Resource Manual for Seasonal and Pandemic Influenza http://www.dshs.state.tx.us/comprep/pandemic/flu%20outreach%20manual%2012-28-2007.pdf Laboratory Services Section http://www.dshs.state.tx.us/lab/

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