Syphilis Serology II Flashcards
FTA-abs:
- what does the name stand for
Fluorescent Treponemal Antibody - Absorbed
FTA-abs:
- definition of “sorbent”
an extract of nonpathogenic treponemes
FTA-abs:
- Why is sorbent used in this test?
It was found that people can have antibodies against nonpathogenic treponemes (people with bad oral hygiene) were causing the test to be falsely positive. So the sorbent is used to absorb out those antibodies and leave the antibodies to pathogenic treponemes
FTA-abs:
- Principle
indirect immunofluorescence
FTA-abs:
- Procedure
Absorption step is performed first. Then Patients antibodies added to a microscope slide with smear of pathogenic treponemes. Ag/Ab binding, then fluorescein-labeled antiseptics globulin is added and you see fluorescence.
FTA-abs:
- Which antigen is used
pathogenic treponemes fixed on a microscope slide
FTA-abs:
- Which form is the antigen in for testing?
either whole organisms or as extracts
FTA-abs:
- what antibody is detected
Treponemal antibodies
FTA-abs:
- appearance of a positive result (antibody present)
green fluorescence (could be 1+ to 4+)
FTA-abs:
- appearance of a negative (antibody absent) result
no fluorescence
FTA-abs:
- Clinical conditions in which a falsely positive result might me anticipated
Other diseases
FTA-abs:
- true positive staining v.s. false positive staining
False positive staining due to antinuclear antibodies that produce a beaded fluorescence, this is NOT a positive result
Serodia TP-PA:
- principle
Passive Agglutination Method
Serodia TP-PA:
- procedure
Extract of pathogenic treponemes is coated on gelatin carrier particles. If treponema antibodies are present, coated gelatin particles will be agglutinated. (also tested against both antigen-uncoated gelatin particles)
Serodia TP-PA:
- antigen used
extract of pathogenic treponemes
Serodia TP-PA:
- antibody detected
Treponemal antibodies
Serodia TP-PA:
- how an absorption step is included in this assay
Patient’s samples are diluted in a buffer containing sorbent with absorbs antibodies against nonpathogenic treponemes.
Serodia TP-PA:
- appearance of a positive (antibody present)
agglutination appears as a layer of cells covering the bottom of the well
Serodia TP-PA:
- appearance of a negative (antibody absent)
No agglutination appears as a button of particles in the center of the well
Multiplex Bead T. pallidum Antibody Testing:
- describe antigen on the bead
Cloned antigens of T. palladium are affixed to microbeads
Multiplex Bead T. pallidum Antibody Testing:
- why is an absorption step not included in the procedure?
because only determinants of pathogenic treponemes are attached to the beads
Traditional Sequence Algorithms
- overview
Screen with Non-treponema Test (usually RPR) (if negative stop)
- if positive -> quantitate RPR -> confirm with treponema test -> if positive then syphilis/ if negative then biological false positive
Traditional Sequence Algorithms
- advantages
Cost effective, useful in monitoring therapy
Traditional Sequence Algorithms
- disadvantages
Too sensitive; negative in early stages
Reverse Sequence Algorithms \
- overview
- Screen with Treponema Test
- Neg = stop; Positive = Non-Treponemal Test (RPR)
- Positive = quantitate and its syphilis (current); Neg= Confirm with Treponema Test
- If pos = syphilis (past/latent); if Neg = False Positive Screening Test
Reverse Sequence Algorithms
- advantages
Diagnostic
- should detect ALL syphilis cases and past infections
- provides results of complete algorithm together rather than awaiting confimatory testing
Technical
- Automated
- Interfaced with LIS computer
Reverse Sequence Algorithms
- disadvantages
Not useful in monitoring treatment or determining re-infection because treponemal antibodies persist forever
At what stages of syphilis are treponema tests positive?
ALL OF THEM!
What serologic tests for syphilis are first to become positive in untreated syphilis?
Treponemal tests
What two infections are related to other treponemes that will cause positive results in the treponema antibody tests
Yaws caused by Treponema pertenue and Pinta caused by Treponema carateum
Can treponemal tests be used to monitor treatment or confirming reinfection of syphilis? why or why not?
No because teponemal antibodies persist forever following syphilis
What one diagnostic test is useful in diagnosing neurosyphilis?
Reagin antibodies detected in CSF by VDRL
- positive result indicates CNS involvement because serum antibodies do not cross into CSF
Congenital syphilis:
- Why must traditional tests for syphilis be interpreted with caution
Treponemes cross placenta to infect fetus, so may be due to moms antibodies; use IgM specific testing or zigzag serologies to confirm infection
Congenital syphilis:
- what test can be done to diagnose?
IgM-specific testing or sequential IgG serologies needed to confirm infant infection
