Syphilis, venous pH, WNV, drug monioring Flashcards
What are the several Syphilis tests available?
What are they used for?
Several tests available:
Venereal Disease Research Laboratory (VDRL)
Rapid Plasma Reagin (RPR)
Fluorescent Treponemal Antibody (FTA)
Used to diagnose and document successful treatment of syphilis
What is Syphilis caused by?
What do the immunologic tests detect?
Syphilis is caused by the spirochete
Treponema pallidum and has four stages – acute, secondary, latent, and tertiary.
The immunologic tests detect antibodies to the bacteria.
There are two groups of antibodies
There are two groups of tests for syphilis, what does each group detect?
The first group of tests (VDRL and RPR) detects the presence of a nontreponemal antibody called reagin, which reacts to phospholipids in the body.
The second group of tests (FTA) detects antibodies directed directly against the Treponema organism itself.
What are the nontreponemal antibody tests?
Specificity?
The first group (nontreponemal antibody tests) are screening tests and are nonspecific and include VDRL and RPR.
The antibodies are detected using the VDRL test.
More sensitive test is the RPR test.
Both these tests, since they test for a nonspecific antibody, have a high false positive rate.
When does VDRL become positive?
VDRL becomes positive 2 weeks after inoculation with bacteria and returns to normal after adequate treatment.
VDRL is positive in almost all primary and secondary stages and in 2/3 of tertiary syphilis
If the VDRL and RPR are positive, what must be done?
If VDRL or RPR is positive, the diagnosis must be confirmed by the more specific FTA test which reacts to a specific treponemal antibody and is more accurate than VDRL or RPR
When does the FTA become positive?
FTA becomes positive 4-6 weeks after inoculation. The FTA test is required before the diagnosis of syphilis can be made with certainty
What must be considered if the VDRL or RPR test positive and the FTA is negative?
If the VDRL or RPR test is positive and the FTA is negative, other diseases that can cause positive results on screening tests must be considered.
Gersten said to NOT memorize these. (malaria, typhus, cat scratch fever, hepatitis, mononucleosis, SLE, acute viral or bacterial infections, lymphogranuloma venereum, hypersensitivity reactions, mycoplasma pneumonia, or recent vaccinations).
For a prenatal checkup, what syphilis tests are done?
Syphilis screening usually is done at the first prenatal checkup of pregnant women with the VDRL test.
If syphilis is a concern then an FTA is performed
If untreated, syphilis can cause abortion, stillbirth, or premature labor as well as CNS damage, hearing loss, or death to the fetus
When does the syphilis test return to normal?
Test returns to normal after successful treatment.
The earlier treatment is done the sooner the tests return to normal.
In primary stage the tests may become negative in 2-4 months, in later stages it may take longer than a year, and in tertiary stage it may never convert to negative.
When is venous pH used? Normal value?
May use venous pH instead of arterial if only concerned about pH and not concerned about oxygen or carbon dioxide. Ex. DKA
Normal Findings: 7.31-7.41
When is testing for West Nile Virus (WNV) indicated?
Most common peak season?
Testing for WNV is indicated when flu-like symptoms occur in an area where the virus exists.
Most common during peak mosquito season (July – October)
What is WNV? How transmitted?
WNV is an RNA virus of the Flavivirus family whose vector is the mosquito.
It is not transmitted from human to human
What does the initial WNV test measure?
When can a diagnosis of WNV be made?
Initial testing measures IgM antibodies to Flaviviruses and is not specific to WNV.
Antibodies are detectable about 10 days after symptoms onset.
If IgM is positive and symptoms meet CDC criteria, the diagnosis of WNV can be made, especially if the person lives in or has traveled to an area than has WNV.
What are the confirmatory tests for WNV that may be used?
Confirmatory tests are the following:
A second IgM test on convalescing serum 3-4 weeks later – should see a four fold increase in level.
Direct detection of WNV RNA
