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48 Cards in this Set

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What agent causes syphilis?
Treponema pallidum
-species pallidum
What are the stages in syphilis?
1. Primary = chancre
2. Sedondy = Rash on trunk
3. Latent = rash may reappear
4. Tertiary= Cardiovascular, neuro, or gummas.
Why are we concerned with syphilis especially?
Can be passed to infants in birth/utero.
What is best diagnostic tool in:
-Primary syphilis
-Secondary syphilis
1' = darkfield microscopy
2' = serology
What is the sensitivity of darkfield microscopy?
app. 75%
What are 3 ways to do directly detect syphilis?
1. Darkfield microscopy
2. DFA
3. PCR
What are the 4 non-treponemal tests, and what are they for?
VDRL, RPR, USR, RST.
-For screening for syphilis during 2ndary stage.
What do all the non-trep tests detect?
IgG and IgM Reagin antibody
What is the antigen that reacts wtih reagin in the tests?
Beef cardiolipin
what are the 3 uses of the nontreponemal tests?
1. Screening for syphilis
2. monitoring treatment effect
3. Diagnose congenital syphilis
what is the preferred test method for congenital syphilis?
RPR
what can cause false pos on the nontrep tests?
1. Produce Ab to other lipid antigens, produced in injury.
2. cross react with other treponemal species.
What should be remembered re: the non-trep screening tests?
-They are qualitative
-Should followup with quantit.
-Prozone is common.
What size needle is used for delivering antigen to the non-treponomal tests?
18 guage
What is VDRL?
venereal disease research lab
what type of test is the VDRL?
what type of specimen?
what is the test good for?
-Flocculation test MICROSCOPIC
-Inactivated serum (csf)
-It's the only test for neurosyphilis, perform on CSF.
What is the principle of the VDRL?
-.5 mL serum + 1 drop antigen
-Rotate 180 RPM, 4 min
-Examine under 10x
what type of test is the RPR?
what type of specimen?
what is the test good for?
-Agglutination MACROSCOPIC
-Serum OR plasma
-Congenital syphilis diagnosis
How does antigen prep vary between the RPR and VDRL?
-No special prep needed for RPR; (VDRL needs immed before use)
What are 3 characteristics of the antigen in the RPR test?
-Choline Cl eliminates need for serum inactivation.
-EDTA stabilizes the Ag
-Charcoal increases visibility.
How does the RPR principle differ/compare to VDRL?
-Uses way less serum; .05 mL
-Both use 1 drop of antigen
-Rotate at 100 rpm only 8 min.
what are 2 other types of nontreponemal tests?
USR (unheated serum reagin test)
RST (Reagin screen test)
when are VDRL and RPR likely to be positive?
at 2ndary syphilic stage
what are 2 uses for Treponemal tests?
-Confirm R/WR screen tests
-Diagnose latent/tertiary syph.
What do treponemal tests detect?
-Detect spfc T. pallidum Abs
What ARE the 2 treponemal tests?
-Microhemagglutination
-FTA-abs
Which test is better during primary syphilis?
FTA-abs
How are the treponemal tests made specific for T. pallidum?
Use T. phagedensis to absorb out non-t. pallidum antibodies.
How does the FTA-abs work?
1. Heatfix dead T. pallidum on slide.
2. Overlay w/ inactive serum; incubate 30 min, 37'C. Rinse
3. Overaly w/ fluor. coomb's, incub 30 min, 37'C. Rinse
4. UV microscope
What are sources of error that alter the FTA-abs test for T. pallidum?
-Hemolysis/bacterial contamination
-Autoimmune disease, pregnancy, other treponomal disease - but few false pos.
What is the essence of microhemagglutination for T. pallidum, what is pos result?
-RBCs sensitz. w/ T. pall Ag.
-Pos = flat matt of agglutin'n across bottom of well.
What are unique requirements for testing for neurosyphilis?
-USE VDRL - only approved test.
-Use 22-23 guage needle.
-Concave slide
-180 rpm, 8 min rotator.
what is a biological false positive?
-caused by a biological disease or agent.
What are 5 causes of BFPs on syphilis tests?
SLE
infectious mono
infectious pneumonia
Pregnancy
Drug addicts
rheumatic fever
What 4 categories of lab methods are used to test for Chlamydia?
1. Cell culture
2. EIA/DFA
3. Serology
4. Nucleic acid testing
What molecules do the various EIA/DFA methods detect?
1. LPS chlamydial antigen
2. Major outer membrane protein (MOMP)
What are advantages of EIA/DFA?
What are disadvantages?
-Inexpensive
-PRetty sensitive - 85-95%
But....
-Specificity lower than NAAT
What serological methods are used for chlamydia?
-Compl. fixation
-Microimmunoflour.
-ELISA
what are advantages of using Nucleic acid probes for chlamydia?
What are disadvantages?
-Has high specificity and can transport stably.
BUt...
Can't use urine; low SENSITIV.
What is the best method for diagnosing chlamydia? Why?
NAAT; it has about 100% specif. and 95% or higher sensitivity.
When CAN'T NAAT be used?
-Within 4 weeks of diagnosis to test for cure, because even dead organisms will be positive.
-On children
What test method can be used for legal cases, and why?
only culture; it is the only one with 100% specificity.
What is the lab's role in diagnosing Herpes simplex 1/2?
Limited; culture would be the best test, but can only be done on unpopped vesicles.
What tests are used for vesicles no longer intact?
-ELISA
-Western blot
What disadvantage affects type-spcfc IgG testing for HSV?
Takes 12 weeks for detectable Ab to rise in primary infections.
what is HPV (papilloma) associated with?
Epithelial cancers of the genital tract.
How is the risk of developing epith cancer of genitalia evaluated?
By HPV serotyping, especially for 16 and 18.
What is the lab's role in diagnosing HPV?
-See dysplasia on pap smear
-Run PCR test called "HC2 hi-risk HPV DNA test.