Saturday, July 8, 2017

Treponemal and nontreponemal tests for syphilis (notes + mnemonic)

Nontreponemal tests include:

Rapid plasma reagin (RPR)
Venereal Disease Research Laboratory (VDRL)
Toluidine Red Unheated Serum Test (TRUST) 

Mnemonic:
Do not trust VDRL rapidly.

Features of non treponemal tests:

They are based upon the reactivity of serum from infected patients to a cardiolipin-cholesterol-lecithin antigen. 

Used for initial syphilis screening due to their relatively low cost, ease of performance, and ability to be quantified for the purpose of following response to therapy.

Specific treponemal tests include:

Fluorescent treponemal antibody absorption (FTA-ABS)
Microhemagglutination test for antibodies to T. pallidum (MHA-TP)
T. pallidum particle agglutination assay (TPPA)
T. pallidum enzyme immunoassay (TP-EIA)
Chemiluminescence immunoassay (CIA)

Features of treponemal tests:

Treponemal tests have been more complex and expensive to perform than nontreponemal tests. Thus, they have traditionally been used as confirmatory tests for syphilis when the nontreponemal tests are reactive.

Treponemal tests are qualitative only and are reported as "reactive" or "nonreactive" 

Once a patient has a positive treponemal test, this test usually remains positive for life. Thus, these tests are generally not useful for confirming a diagnosis of syphilis in a patient with prior treated disease.

That's all!
-IkaN

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