Syphilis Serology II

Question 1

FTA-abs:

- what does the name stand for

Answer 1

Fluorescent Treponemal Antibody - Absorbed

Question 2

FTA-abs:

- definition of “sorbent”

Answer 2

an extract of nonpathogenic treponemes

Question 3

FTA-abs:

- Why is sorbent used in this test?

Answer 3

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

Question 4

FTA-abs:

- Principle

Answer 4

indirect immunofluorescence

Question 5

FTA-abs:

- Procedure

Answer 5

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.

Question 6

FTA-abs:

- Which antigen is used

Answer 6

pathogenic treponemes fixed on a microscope slide

Question 7

FTA-abs:

- Which form is the antigen in for testing?

Answer 7

either whole organisms or as extracts

Question 8

FTA-abs:

- what antibody is detected

Answer 8

Treponemal antibodies

Question 9

FTA-abs:

- appearance of a positive result (antibody present)

Answer 9

green fluorescence (could be 1+ to 4+)

Question 10

FTA-abs:

- appearance of a negative (antibody absent) result

Answer 10

no fluorescence

Question 11

FTA-abs:

- Clinical conditions in which a falsely positive result might me anticipated

Answer 11

Other diseases

Question 12

FTA-abs:

- true positive staining v.s. false positive staining

Answer 12

False positive staining due to antinuclear antibodies that produce a beaded fluorescence, this is NOT a positive result

Question 13

Serodia TP-PA:

- principle

Answer 13

Passive Agglutination Method

Question 14

Serodia TP-PA:

- procedure

Answer 14

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)

Question 15

Serodia TP-PA:

- antigen used

Answer 15

extract of pathogenic treponemes

Question 16

Serodia TP-PA:

- antibody detected

Answer 16

Treponemal antibodies

Question 17

Serodia TP-PA:

- how an absorption step is included in this assay

Answer 17

Patient’s samples are diluted in a buffer containing sorbent with absorbs antibodies against nonpathogenic treponemes.

Question 18

Serodia TP-PA:

- appearance of a positive (antibody present)

Answer 18

agglutination appears as a layer of cells covering the bottom of the well

Question 19

Serodia TP-PA:

- appearance of a negative (antibody absent)

Answer 19

No agglutination appears as a button of particles in the center of the well

Question 20

Multiplex Bead T. pallidum Antibody Testing:

- describe antigen on the bead

Answer 20

Cloned antigens of T. palladium are affixed to microbeads

Question 21

Multiplex Bead T. pallidum Antibody Testing:

- why is an absorption step not included in the procedure?

Answer 21

because only determinants of pathogenic treponemes are attached to the beads

Question 22

Traditional Sequence Algorithms

- overview

Answer 22

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

Question 23

Traditional Sequence Algorithms

- advantages

Answer 23

Cost effective, useful in monitoring therapy

Question 24

Traditional Sequence Algorithms

- disadvantages

Answer 24

Too sensitive; negative in early stages

Question 25

Reverse Sequence Algorithms \

- overview

Answer 25

1. Screen with Treponema Test
2. Neg = stop; Positive = Non-Treponemal Test (RPR)
3. Positive = quantitate and its syphilis (current); Neg= Confirm with Treponema Test
4. If pos = syphilis (past/latent); if Neg = False Positive Screening Test

Question 26

Reverse Sequence Algorithms

- advantages

Answer 26

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

Question 27

Reverse Sequence Algorithms

- disadvantages

Answer 27

Not useful in monitoring treatment or determining re-infection because treponemal antibodies persist forever

Question 28

At what stages of syphilis are treponema tests positive?

Answer 28

ALL OF THEM!

Question 29

What serologic tests for syphilis are first to become positive in untreated syphilis?

Answer 29

Treponemal tests

Question 30

What two infections are related to other treponemes that will cause positive results in the treponema antibody tests

Answer 30

Yaws caused by Treponema pertenue and Pinta caused by Treponema carateum

Question 31

Can treponemal tests be used to monitor treatment or confirming reinfection of syphilis? why or why not?

Answer 31

No because teponemal antibodies persist forever following syphilis

Question 32

What one diagnostic test is useful in diagnosing neurosyphilis?

Answer 32

Reagin antibodies detected in CSF by VDRL

- positive result indicates CNS involvement because serum antibodies do not cross into CSF

Question 33

Congenital syphilis:

- Why must traditional tests for syphilis be interpreted with caution

Answer 33

Treponemes cross placenta to infect fetus, so may be due to moms antibodies; use IgM specific testing or zigzag serologies to confirm infection

Question 34

Congenital syphilis:

- what test can be done to diagnose?

Answer 34

IgM-specific testing or sequential IgG serologies needed to confirm infant infection