Syphilis and spirochetes Flashcards
In the former question, if the patient’s physician still suspects syphilis, what testing could best confirm
or rule out the diagnosis?
FTA-Abs on serum and a darkfield exam on the genital lesion
Which quality control data set represents acceptable results for the RPR test? (It may help to refer to
your upcoming Syphilis RPR lab)
Temp: 24 degrees C Rotation speed: 100 rpm/min Needle drops: 30 in 0.5 cc
Which of the following is true of reagin?
It is an antibody-like substance directed against cardiolipin
What is the principle of the methodology of the RPR tests?
Flocculation: Antigen is a carbon particle-cardiolipin which tests for non-specific reagin (antibody-like)
substance
In the fluorescent treponemal antibody absorption test (FTA-ABS), what is the purpose of absorption
with Reiter treponemes?
The Reiter strain is used as a sorbent to remove antibodies to nonpathological strains of treponeme
A syphilis test that does not detect specific treponemal antibodies is:
RPR
A baby is born to a mother who is in the latent stage of syphilis. The baby exhibits no symptoms of the
disease at birth, but a cord blood RPR and a total FTA-ABS is positive, IgM FTA-Abs is negative. How
should these results be handled?
Repeat tests over several month and look for a rise in titer of the RPR and FTA-Abs to determine if the
positivity is due to transplacental passage of mother’s antibodies or production of antibodies by the baby
Which of the following is true of treponemal tests for syphilis?
They should be used as confirmatory tests rather than for screening
An RPR test done on a 19-year old female as part of a prenatal work-up seemed negative but exhibited a rough appearance.
What, if anything, is (are) the BEST next step(s) you should take? (Select all that apply)
If in question, send off for confirmatory testing
Check to make sure prozone is not occurring
A “rough” (less than minimally reactive but still not negative) reaction may be an indication of
prozone and a very high titer; it may also be an indicator of a false positive. Most labs dilute
the sample first. If the results do not show evidence of prozone, then the sample should be
evaluated by an alternative method
From which sample can a + darkfield exam be performed on a newborn to assist with the diagnosis of congenital syphilis
genital lesion
skin rash
nasopharynx in newborn babies with syphilis
Which serum antibody response usually characterizes the primary (early) stage of syphilis?
Detected 1-4 weeks after the appearance of the primary chancre
An RPR card test performed on a spinal fluid sample was non-reactive. The physician was skeptical
and asked for a repeat test on the spinal fluid. The RPR result was reactive at a 1:1 dilution. The
result:
Is unreportable; the RPR card test should not be performed on spinal fluid
What is the most likely interpretation of the following syphilis serology restults?
RPR : Reactive
VDRL: Reactive
FTA-Abs: Neg
EIA Test: Neg
Darkfield Exam: Neg
Biological false positive
Cholesterol is added to the antigen used in flocculation tests for syphilis to
increase sensitivity of the antigen
A 21 year old female suffering from systemic lupus erythermatosus (SLE) and an ear infection is
tested for syphilis using the RPR card test. The result is reactive. The patient denies any sexual
activity. A repeat test 8 month later is still reactive although the ear infection has resolved. The most
likely explanation for these results and a test that can confirm the presence of syphilis are:
chronic biological false positive due to SLE FTA-Abs
The RPR test is often considered to be an improvement over the VDRL because of the following:
charcoal has been added to help visualization of the reaction
choline chloride has been added to destroy complement thus eliminating the need to heat inactivate
A VDRL serum sample is heat inactivated then placed in a refrigerator for overnight storage. Before
being tested, the serum must be:
reheated to 56 degrees C for 10 minutes
Flocculation tests for syphilis detect the presence of:
reagin
Cause of syphilis
Treponema pallidum
T. pallidum can survive in what hosts?
humans and footpads of armadillos
spread of syphilis is
direct contact
Can T. pallidum breach skin?
yes
Treponomes are destroyed by
heat, cold, drying
what percentage of individuals exposed to a primary lesion contact syphilis?
30-50%
