Diagnostic Tests for

Influenza: the Tortoise and

the Hare

Arthur E. Crist, Jr., Ph.D.Director, Clinical MicrobiologyDirector, Clinical Microbiology

Ph. (717) 851-2393Ph. (717) 851-2393E-mail: acrist@wellspan.orgE-mail: acrist@wellspan.org

Influenza Virus - Schematic

17

Laboratory Diagnosis of Influenza

Retrospective, requires paired sera>2 weeksSerology

Widely available, requires little expertise15-30 minutesAntigen Detection

(Rapid EIA-like)

Requires reading expertise & IF microscope2-4 hoursAntigen Detection

(IF)

Becoming gold standard(?), requires expertise & expensive equipment

2-4 hoursMolecular(RT-PCR)

Still gold standard(?), requires expertise, provides virus for studies

1-10 daysCulture

CommentsTime to ResultsTestMethod

Conventional Cell CultureConventional Cell Culture– Inoculation of specimens into cell culture: Inoculation of specimens into cell culture:

Madin-Darby canine kidney cell line Madin-Darby canine kidney cell line (MDCK), primary rhesus monkey kidney (MDCK), primary rhesus monkey kidney cells (RMK), Vero cells, MRC-5 human cells (RMK), Vero cells, MRC-5 human diploid embryonic lung fibroblastsdiploid embryonic lung fibroblasts

– If CPE, hemadsorption (HAD) with 0.5% If CPE, hemadsorption (HAD) with 0.5% suspension guinea pig red blood cells suspension guinea pig red blood cells followed by DFA if positivefollowed by DFA if positive

– In the absence of CPE, “blind” (HAD) at In the absence of CPE, “blind” (HAD) at days 2 and 7 followed by FA if positivedays 2 and 7 followed by FA if positive

Cell CultureCell Culture

Will cell culture replace fertilized Will cell culture replace fertilized eggs?eggs?

Uninfected Infected

Cell Culture - CPECell Culture - CPE

Hemadsorption

Hemadsorption Hemadsorption +DFA+DFA

Shell Vial Cell CultureShell Vial Cell Culture

The use of shell vials for more rapid The use of shell vials for more rapid isolation and identification of Influenzaisolation and identification of InfluenzaMDCK, RMK, mink lung cells (Mv1Lu)MDCK, RMK, mink lung cells (Mv1Lu)R-Mix: Mv1Lu and A549 cellsR-Mix: Mv1Lu and A549 cellsCentrifugationCentrifugation– shell vials inoculated, incubated, and “blind” shell vials inoculated, incubated, and “blind”

stained at day 1 and 5 for Influenza A and B stained at day 1 and 5 for Influenza A and B

Fong, C.K.Y., et. al. 2000. J. Clin. Microbiolo. 38: 4660-4662

Huang, V.T., et al. 2000. J. Clin. Microbiol. 38: 422-423

Performance of RT-PCR, Shell Vial, Performance of RT-PCR, Shell Vial, and Tube Culture for Influenzaand Tube Culture for Influenza

Zitterkopf, N.L., et. al. 2006. J. Clin. Microbiol. 44: 3366-3367

Comparison of Culture, Serology and Comparison of Culture, Serology and PCR Diagnostic TestsPCR Diagnostic Tests

Concordance of positive results with three testConcordance of positive results with three testmethodsmethods

11

418 (43%)

116

41

97 428

Serology Serology (61%)(61%)

RT-PCR RT-PCR (70%)(70%)

Culture Culture (55%)(55%)

Direct and Indirect FA Tests:Direct and Indirect FA Tests:Direct Specimen Testing or Culture ConfirmationDirect Specimen Testing or Culture Confirmation

Bartels/IntracelBartels/Intracel

Monoclonal AntibodiesMonoclonal AntibodiesIndirect ProcedureIndirect Procedure– 11oo Antibody - 30 min Antibody - 30 min– Conjugate - 30 minConjugate - 30 minApproved for culture Approved for culture confirmation and direct confirmation and direct specimen detectionspecimen detection

ChemiconChemicon

Light DiagnosticsLight DiagnosticsMonoclonal AntibodiesMonoclonal AntibodiesDirect - 30 minDirect - 30 minApproved for culture Approved for culture confirmation and direct confirmation and direct specimen detectionspecimen detection

ChemiconChemicon

SimulFluorSimulFluorTMTM

Dual color fluorescence: Flu A Dual color fluorescence: Flu A and Flu B detection in one welland Flu B detection in one wellDirect - 30 minDirect - 30 minApproved for culture Approved for culture confirmation and direct confirmation and direct specimen detectionspecimen detection

DAKODAKO

ImagenImagenTMTM

Monoclonal AntibodiesMonoclonal AntibodiesDirect ProcedureDirect ProcedureConjugated Ab - 15 minConjugated Ab - 15 minApproved for culture Approved for culture confirmation and direct confirmation and direct specimen detectionspecimen detection

Flu B

Flu A

Diagnostic ProductsDiagnostic Products

Monoclonal AntibodiesMonoclonal AntibodiesDirect ProcedureDirect Procedure– 15 min - Package insert15 min - Package insert– 30 min works better30 min works betterApproved for direct Approved for direct specimen and culture specimen and culture confirmation testingconfirmation testing

FA - AdvantagesFA - Advantages

Relatively inexpensiveRelatively inexpensiveAmenable to batch testingAmenable to batch testingRapid (1-2 hrs)Rapid (1-2 hrs)Able to assess specimen qualityAble to assess specimen quality

FA - DisadvantagesFA - Disadvantages

Subjective readSubjective readHigh complexity testHigh complexity testFluorescent microscopeFluorescent microscopeHighly trained personnelHighly trained personnelLonger turnaround timesLonger turnaround times

Rapid Influenza AssaysRapid Influenza AssaysEnzyme Immunoassay (EIA)Enzyme Immunoassay (EIA) Directigen Flu A and Directigen Flu A+B Directigen Flu A and Directigen Flu A+B

(Becton Dickinson) (Becton Dickinson) Endogenous Viral-Encoded Assay (EVEA)Endogenous Viral-Encoded Assay (EVEA) ZstatFlu (ZymeTx)ZstatFlu (ZymeTx)

Optical Immunoassay (OIA)Optical Immunoassay (OIA) Flu OIA (Biostar)Flu OIA (Biostar)

Lateral-Flow Immunoassay (LFIA)Lateral-Flow Immunoassay (LFIA) QuickVue Influenza (Quidel)QuickVue Influenza (Quidel)

CLIA StatusCLIA Status

Moderate ComplexityModerate ComplexityDirectigen Flu ADirectigen Flu ADirectigen Flu A+BDirectigen Flu A+BFlu OIAFlu OIA

Waived StatusWaived StatusQuickVue InfluenzaQuickVue InfluenzaZstatFluZstatFlu

Test Specimen VTM? Swabs Directigen

Flu A NP wash/ aspirate (pref) NP & Throat swab, OK

OK Rayon or dacron. Can purchase separately

Directigen Flu A+B

NP wash/ aspirate (pref) NP, nasal, & throat swab OK

OK Rayon or dacron. Can purchase separately

ZstatFlu Throat swab No Foam-tipped. Included in kit

Flu OIA Nasal aspirate, NP swab, throat swab, sputum

No Included in kit. Can purchase separately

QuickVue Influenza

Nasal swab, wash, aspirate

No Foam tipped. Included in kit

Comparison of Rapid TestsComparison of Rapid Tests

Comparison of Rapid TestsComparison of Rapid Tests

Test Steps* Assay Time*

(minutes)

Hands Time*

(minutes)

Specimen Storage

Directigen Flu A 10 15-20 15-20 2-8C / No

defined limit Directigen Flu A+B 10 15-20 7 2-8C / No

defined limit

ZstatFlu 6 30 10 0-40C / 24 hr.

FLU OIA 10 35-40 10-15 2-8C / 24 hr. QuickVue Influenza 3 10-15 5 2-8C / 1 hr.

Directigen Flu A TestDirectigen Flu A Test Directigen Flu A+B Assay Directigen Flu A+B Assay

ZstatFluZstatFlu

ZstatFluZstatFlu

Biostar Flu OIABiostar Flu OIA

Biostar OIABiostar OIA

QuickVue InfluenzaQuickVue Influenza

Comparison of Rapid TestsComparison of Rapid Tests

Test

Sensitivity

Specificity Directigen

Flu A 67-92% 88-97%

Directigen Flu A+B

(A) 77-95%

(B) 71-88%

(A) 90-91%

(B) 98-100%

ZstatFlu 57-65% 98-100%

FLU OIA 62-88% 52-80% QuickVue Influenza 73-81% 96-99%

Prevalence rates were all >18%

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Laboratory Diagnosis of Influenza Rapid EIA-Like Tests

A & BNon-WaivedClearview Flu A/B

A & BNon-waivedDirectigen EZ Flu A + B

A & BNon-waivedFlu OIA A/B

A / BNon-waivedFlu OIA

A & BNon-waivedDirectigen Flu A & B

A & BWaivedBinaxNOW Influenza A & B

A & BWaived/Non-waivedNOW Flu A and NOW Flu B

ANon-waivedDirectigen Flu A

Antigen DetectedCLIA StatusTest

19

Laboratory Diagnosis of Influenza Rapid EIA-Like Tests (continued)

A & BNon-WaivedSAS Influenza A and Influenza B

A & BNon-waivedXpect Flu A & B

A & BWaivedQuickVue Influenza A + B

A / BWaivedQuickVue Influenza

A / BWaivedZstatFlu

Antigen DetectedCLIA StatusTest

Performance CharacteristicsPerformance CharacteristicsTestTest SensitivitySensitivity SpecificitySpecificity

Directigen Directigen Flu AFlu A

91% (A)91% (A) 95% (A)95% (A)

Directigen Directigen Flu A & BFlu A & B

86% (A) 81% (B)86% (A) 81% (B) 91% (A) 99.5% (B)91% (A) 99.5% (B)

Flu OIAFlu OIA 62-88% (A/B)62-88% (A/B) 52%-80% (A/B)52%-80% (A/B)

Flu OIA A/BFlu OIA A/B 62%-88% (A/B)62%-88% (A/B) 52%-80% (A/B)52%-80% (A/B)

NOW Flu A & BNOW Flu A & B 78%-82% (A)78%-82% (A)58-71% (B)58-71% (B)

92-94% (A) 97% (B)92-94% (A) 97% (B)

Performance CharacteristicsPerformance CharacteristicsTestTest SensitivitySensitivity SpecificitySpecificity

QuickVueQuickVue InfluenzaInfluenza

73-81% (A/B)73-81% (A/B) 95% (A)95% (A)

QuickVueQuickVue Influenza A&BInfluenza A&B

72-77% (A) 72-77% (A) 73-82% (B)73-82% (B)

91% (A)91% (A)99.5% (B)99.5% (B)

SAS InfluenzaSAS Influenza A A & Influenza B& Influenza B

76% (A)76% (A)91% (B)91% (B)

98% (A)98% (A)100% (B)100% (B)

Xpect Flu A &Xpect Flu A & BB 92% (A)92% (A)98% (B)98% (B)

100% (A)100% (A)100% (B)100% (B)

ZstatFluZstatFlu 58-65% (A/B)58-65% (A/B) 98-100% (A/B)98-100% (A/B)

Rapid (POC)Tests: AdvantagesRapid (POC)Tests: Advantages

Rapid turn around timeRapid turn around timeRapid outbreak identificationRapid outbreak identificationCost-effective (?)Cost-effective (?)Widespread testing availableWidespread testing availableLess expertise requiredLess expertise requiredOptimize antibiotic and antiviral usageOptimize antibiotic and antiviral usage

Rapid Tests: ConcernsRapid Tests: ConcernsSpecimen adequacySpecimen adequacyNo viral isolates available for further No viral isolates available for further characterizationcharacterizationLoss of surveillance dataLoss of surveillance dataLive, attenuated intranasal vaccine can Live, attenuated intranasal vaccine can produce positive results (culture positive produce positive results (culture positive too!)too!)Variable performance characteristicsVariable performance characteristicsResult interpretation- poor positive Result interpretation- poor positive predictive values during low prevalencepredictive values during low prevalence– Improper treatment choices Improper treatment choices

Percent Positive By Specimen TypePercent Positive By Specimen Type

Covalciuc, K.A., et al. 1999. J. Clin.Microbiol. 37: 3971-3974

Patient Age and Onset of TestingPatient Age and Onset of Testing

Steininger, C., et al. 2002. J. Clin. Microbiol. 40: 2051-2056

a No samples were in the category of 25 to 50 positive cells.

EIA resultNo. of samples with indicated no. of cells positive by DFAa

<5 5-10 11-25 50-100 >100 >1,000 Total

Negative 8 1 3 2 1 0 15

Positive 0 1 2 2 5 6 16

Total 8 2 5 4 6 6 31

Correlation between number of DFA-positive cells and EIA result

Predictive ValuePredictive ValueThe probability of the presence or The probability of the presence or absence of disease given the test resultabsence of disease given the test result– PPV is the probability of disease in a patient with PPV is the probability of disease in a patient with

a positive test resulta positive test result– NPV is the probability of not having disease when NPV is the probability of not having disease when

the test result is negative.the test result is negative.Determined by Determined by – sensitivity and specificity of the testsensitivity and specificity of the test– prevalence of disease in the population prevalence of disease in the population

being testedbeing tested

Hypothetical Influenza Test PerformanceHypothetical Influenza Test PerformancePrevalence = 1 in 5Prevalence = 1 in 5– Sensitivity = 95%Sensitivity = 95%– Specificity = 96%Specificity = 96%

– PPV = 85.6%PPV = 85.6%– NPV = 96%NPV = 96%

Prevalence = 1 in 100Prevalence = 1 in 100– Sensitivity = 95%Sensitivity = 95%– Specificity = 96%Specificity = 96%

– PPV = 19.2%PPV = 19.2%– NPV = 99.9%NPV = 99.9%

Which test is best? Know the test performance characteristics and the epidemiology of the disease

False Positive EIA’sFalse Positive EIA’s

Tampa, FL - 16 Flu A positives by EIA in Tampa, FL - 16 Flu A positives by EIA in the period from August to the end of the period from August to the end of October – none confirmedOctober – none confirmedNY State Dept. of Health (December NY State Dept. of Health (December 2006) 2006) 60 specimens that were flu EIA positive sent for confirmatory testing. Only one of them positive by RT-PCR

Rapid Tests: Optimizing UseRapid Tests: Optimizing Use

Educate clinicians on predictive values Educate clinicians on predictive values & limitations of test results& limitations of test resultsConfirm early, late and out-of-season Confirm early, late and out-of-season positivespositivesConfirm peak-season negatives, if Confirm peak-season negatives, if applicableapplicableUse prevalence indicators to decide:Use prevalence indicators to decide:– When to testWhen to test– When to qualify resultWhen to qualify result– When to confirm resultsWhen to confirm results

"Don't brag about your lightning pace, "Don't brag about your lightning pace, for Slow and Steady won the race!"for Slow and Steady won the race!"

A sculpture of the Tortoise and the Hare by Nancy A sculpture of the Tortoise and the Hare by Nancy Schön. Located at Copley Square, it represents the Schön. Located at Copley Square, it represents the

finish line of the Boston Marathonfinish line of the Boston Marathon