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CDC National Infertility Prevention Project CDC National Infertility Prevention Project

CDC National Infertility Prevention Project - PowerPoint Presentation

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CDC National Infertility Prevention Project - PPT Presentation

Laboratory Update Region I Wells Beach Maine June 13 2009 Richard Steece PhD DABMM DrRSteeceaolcom Chlamydia and Gonorrhea 102 Tests Old and New Test Performance Issues ID: 727663

x100 ppv test specificity ppv x100 specificity test 100 npv prevalence tests prevalencesensitivity 0095 specimens laboratory sensitivity acid large positive advantages amplified

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Slide1

CDC National Infertility Prevention ProjectLaboratory UpdateRegion IWells Beach, MaineJune 1-3, 2009

Richard

Steece

, Ph.D., D(ABMM)

DrRSteece@aol.comSlide2

Chlamydia and Gonorrhea “102”Tests - Old and NewTest Performance IssuesSensitivity/SpecificityPositive Predictive Value (PPV)Negative Predictive Value (NPV)Frequently Asked Questions (FAQ)Slide3

Chlamydia Laboratory MethodsCulture (Cell Culture) Slide4

Advantages/DisadvantagesCell CultureADVANTAGESUsed for many types of specimens, e.g. endocervical, urethral, rectal, ocular, etc.Meets medico-legal standards (specificity)Used for strain studies (DNA fingerprinting)Susceptibility testing possibleDISADVANTAGESComparatively expensiveMany variables involved, e.g. cell culture, medium, etc.

Technically more difficult than many non-culture tests

Delayed turn around time

Lack of sensitivity (compared to amplified tests)Slide5

Chlamydia Laboratory MethodsNon-cultureANTIGEN DETECTION Direct Fluorescent Antibody (DFA) Enzyme Immunoassay (EIA)NUCLEIC ACID DETECTION METHODS Nucleic Acid Probe (GenProbe) Hybrid Capture (Digene)Slide6

Advantages/Disadvantages Non-cultureADVANTAGESUsed for many types of specimens, e.g. endocervical, urethral, rectal, ocular, etc. (DFA)Effective for large scale screening (EIA/NAP)Viable organism not requiredEvaluate quality of specimens (DFA)InexpensiveRapid turn around timeDISADVANTAGES

Not suitable for large volume testing (DFA)

Lack of sensitivity (compared to amplified tests)

Not FDA cleared for alternate specimens, e.g. urine, etc.Slide7

Chlamydia Laboratory Methods Non-cultureNucleic Acid Amplification Tests (NAATs) Roche AMPLICOR® CT/NG Test (PCR)Roche COBAS AMPLICOR™ CT/NG Test (PCR)GenProbe APTIMA COMBO 2® (TMA) GenProbe APTIMA CT® (TMA)BD ProbeTec™ ET (SDA)BD

ProbeTec

Chlamydia

trachomatis

(CT)

Qx

Amplified DNA Assay (SDA)

Abbott

RealTime

CT/NG (PCR)Slide8

Advantages/DisadvantagesNAATsADVANTAGESMost sensitive and specific testsEffective for large scale screeningRapid turn around timeNAATs are FDA cleared for urine specimensMay be used with some alternate specimensDISADVANTAGESSome versions not suitable for large volume screeningHigh technical skill requiredSpecial facilities or clean area requiredExpensive Slide9

Chlamydia Rapid TestsPoint of Care Tests (POCTs)Wampole ClearviewQuidel Quickview - InvernessSlide10

Advantages/DisadvantagesPOCTsADVANTAGESRapid turn around timeAllows treatment of patient while in clinicDISADVANTAGESExpensiveNot suitable for large volume screeningPoor sensitivity with some POCTs Complexity non-waived Slide11

Gonorrhea Laboratory MethodsCultureThayer Martin, etc.Genetic transformation (Gonostat)Direct Microscopic ExamGram StainSlide12

Advantages/DisadvantagesBacterial CultureADVANTAGESAll types of specimens, e.g. endocervical, urethral, rectal, pharyngeal, ocular, etc.Meets medico-legal standards (specificity)Used for strain studies fingerprintingSusceptibility testing possibleDISADVANTAGESSome variables, e.g. various culture, media, etc.Delayed turn around timeLack of sensitivity (compared to amplified tests)Slide13

GonorrheaLaboratory MethodsNon-CultureNucleic acid detection methodNucleic Acid Probe (GenProbe)Hybrid Capture (Digene)Slide14

Advantages/DisadvantagesNAP and NAPSAADVANTAGESEffective for large scale screeningViable organism not requiredRapid turn around timeInexpensiveModerate technical skill requiredDISADVANTAGESLack of sensitivity (compared to amplified tests)Not FDA cleared for alternate specimens, e.g. urine, etc.Slide15

Gonorrhea Laboratory MethodsNucleic Acid Amplification Tests (NAATs) Roche AMPLICOR® CT/NG Test (PCR)Roche COBAS AMPLICOR™ CT/NG Test (PCR)GenProbe APTIMA COMBO 2® (TMA) GenProbe APTIMA GC® (TMA)BD ProbeTec™ ET (SDA)BD

ProbeTec

Neisseria

gonorrhoeae

(GC)

Qx

Amplified DNA Assay (SDA)

Abbott

RealTime

CT/NG (PCR)Slide16

Advantages/DisadvantagesNucleic Acid Amplified Tests (NAATs)ADVANTAGESMost sensitive and specific testsEffective for large scale screeningRapid turn around timeNAATs are FDA cleared for urine specimensMay be used with some alternate specimens DISADVANTAGESSome versions not suitable for large volume screeningHigh technical skill requiredSpecial facilities or clean area requiredExpensiveSlide17

Test Performance IssuesSensitivity – The ability of a test to detect patients who have the disease or condition for which they are being tested OR refers to the proportion of people with disease who have a positive test.Specificity – The ability of a test to identify patients who do not have the disease or condition for which they are being tested OR

refers to the proportion of people without disease who have negative test result.Slide18

Positive Predictive Value (PPV)The likelihood that an individual with a positive test has the disease.Negative Predictive Value (NPV)The likelihood that a person with a negative test does not have the disease.Slide19

Performance estimates1 of different tests to detect chlamydia and gonorrhea Sensitivity, % Specificity,%CT Culture 40-70 >99GC Culture 45-65 >99DFA 50-70 95-99EIA 60-70 95-99NAP/NAPSA 60-75 97-99NAATs

95-98

>99

1

Performance estimates vary widely due to differences in statistical analysisSlide20
Slide21

Example of NPV using PrevalenceSensitivity is 95%Specificity is 99%Prevalence is 20.0% NPV=(1-.20)(.99)/(1-.20)(.99)+(.20)(1-.95)x100NPV=.792/.792(.01)x100

NPV=.9875

x 100 =

NPV

of

99%Slide22

Example of NPV using PrevalenceSensitivity is 95%Specificity is 99%Prevalence is 20.0% NPV=(1-.20)(.99)/(1-.20)(.99)+(.20)(1-.95)x100NPV=.792/.792+(.01)x100

NPV=.9875

x 100 =

NPV

of

99%

Sensitivity is 85%

NPV=.9635 x 100 =

NPV of 96%Slide23

Graph Courtesy of Abbot LaboratoriesSlide24

Example of PPV using PrevalenceSensitivity is 95%Specificity is 99%Prevalence is 20.0% PPV=(.20)(.95)/(.20)(.95)+(1-.20)(1-.99)x100

PPV

=.19/.19+(.008)x100

PPV

=.9595

x 100 = PPV of

96%Slide25

Example of PPV using PrevalenceSensitivity is 95%Specificity is 99%Prevalence is 15.0% PPV=(.15)(.95)/(.15)(.95)+(1-.15)(1-.99)x100

PPV

=.1425/.1425+(.0085)x100

PPV

=.9437

x 100 = PPV of

94%Slide26

Example of PPV using PrevalenceSensitivity is 95%Specificity is 99%Prevalence is 10.0% PPV=(.10)(.95)/(.10)(.95)+(1-.10)(1-.99)x100

PPV=.

095/.095+(.009)x100

PPV

=.9134

x 100 = PPV of

91%Slide27

Example of PPV using PrevalenceSensitivity is 95%Specificity is 99%Prevalence is 5.0% PPV=(.05)(.95)/(.05)(.95)+(1-.05)(1-.99)x100

PPV=.

0475/.0475+(.0095)x100

PPV

=.8333

x 100 = PPV of

83%Slide28

Example of PPV using PrevalenceSensitivity is 95%Specificity is 99%Prevalence is 2.0% PPV=(.02)(.95)/(.02)(.95)+(1-.02)(1-.99)x100

PPV=.

019/.019+(.0098)x100

PPV

=.6597

x 100 = PPV of

66%Slide29

Example of PPV using PrevalenceSensitivity is 95%Specificity is 99%Prevalence is 1.0% PPV=(.01)(.95)/(.01)(.95)+(1-.01)(1-.99)x100

PPV=.

0095/.0095+(.0099)x100

PPV

=.4896

x 100 = PPV of

49%Slide30

Example of PPV using Prevalence(Effect of repeating positive specimens)1-(1-Spec.)2 = 1-(1-.99)2 = 1-(.0001) = 99.99%Sensitivity remains 95%Revised Specificity is 99.99% Prevalence is 1.0%PPV=(.01)(.95)/(.01)(.95)+(1-.01)(1-.9999) x 100

PPV=.

0095/.0095+(.000099)

x 100

PPV=.

9896

x 100 =

PPV of

99%

(49%)Slide31

Graph Courtesy of Abbot LaboratoriesSlide32

Example of PPV using PrevalenceSensitivity is 95%Specificity is 99.9%Prevalence is 1.0% PPV=(.01)(.95)/(.01)(.95)+(1-.01)(1-.999)x100

PPV=.

0095/.0095+(.00099)x100

PPV

=.9056

x 100 =

PPV of

91%Slide33

Example of PPV using PrevalenceSensitivity is 95%Specificity is 99.9%Prevalence is 1.0% PPV=(.01)(.95)/(.01)(.95)+(1-.01)(1-.999)x100

PPV=.

0095/.0095+(.00099)x100

PPV

=.9056

x 100 = PPV of

91%

Specificity is 99.99%, PPV of 99%Slide34

Question: How long after a patient has successfully completed appropriate antimicrobial therapy would you be able to detect antigen in their specimen (e.g. false positive) due to residual CT or GC DNA/RNA? Answer: The current

CDC Treatment (and

Laboratory

) Guidelines

state

that DNA or RNA may persist for up to 3 weeks after the successful completion of appropriate

antimicrobial therapy. At

the

recent laboratory guidelines meeting, the expert panel recommended

that this statement remain the same at this

time. However

, studies are being conducted to examine this with several "newer"

NAATs and

it

is possible this recommendation may change

in the

future based on new data.

Frequently Asked Questions (FAQ)Slide35

Question: How soon after a patient has unprotected sex would you be able to detect CT and/or GC with a nucleic acid amplification test (NAAT)? Answer: Depending on the antigen load (i.e. amount of CT or GC in the ejaculate), a patient’s specimen

could be positive very shortly after exposure (sex/rape/abuse), before actual infection,

from minutes to hours

after sex to

upwards of several days

.  If infection occurs there should be a latent or silent (undetectable) period for a

short time

.  Once again depending on antigen load, a positive (if the individual becomes infected) could be detected in some cases in as little as a week, looking at the life cycle of the organism.  However, the average time from actual infection to detectable shedding is more likely 2-4 weeks for CT, most likely a week sooner for GC. 

Frequently Asked Questions (FAQ)Slide36

Question: Is test-of-cure recommended as a routine procedure after therapy for CT or GC infection with first-line CDC-recommended treatment regimens?Answer: The

guidelines do not recommend a test of cure for CT or GC, with a few exceptions

Frequently Asked Questions (FAQ)Slide37

Lots of tearsThe End - QuestionsSlide38

Question: In the past our laboratory has given us the option of submitting urine or endocervical swabs on our patient/clients. Recently they have verified rectal swabs as an additional specimens. Is it possible to just send in rectal swabs instead of urine or endocervical?Answer: Rectal swabs are not recommended for patients unless they have participated in anal sex.

Frequently Asked Questions (FAQ)