Bejel laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
Laboratory Findings
Syphilis Serology
Nontreponemal (reagin) Test
- Treponemal (specific) Test
- Rapid plasma reagin (RPR) test
- Venereal Disease Research Laboratory (VDRL) test
- Toluidine red unheated serum test (TRUST)
Treponemal (specific) Test
- Rapid plasma reagin (RPR) test
- Venereal Disease Research Laboratory (VDRL) test
- Toluidine red unheated serum test (TRUST)
- Fluorescent treponemal antibody-absorption (FTA-ABS) test
- Treponema pallidum immobilization (TPI) test
- Treponema pallidum particle agglutination assay (TPPA)
- Enzyme immune assay (EIA) or enzyme-linked immunosorbent assay (ELISA)
- Chemiluminescence immunoassay
- Chromatographic point of contact (POC) tests
Serologic tests for syphilis include screening tests that use nonspecific cardiolipin antigens and confirmatory tests that use specific T. pallidum antigens (Table 1). A nontreponemal test such as Venereal Disease Research Laboratory (VDRL), rapid plasma reagin (RPR) or an equivalent test may be used for screening. Positive results on these nontreponemal tests should be confirmed by using a treponemal test, such as fluorescent treponemal antibody absorption (FTA-ABS) or other treponemal test.
Screening tests such as the VDRL and RPR are relatively simple to perform and provide rapid results. However, interpretation of results demands trained personal. In addition, laboratory equipment and quality control can present challenges in non-U.S. settings. Both VDRL and RPR quantitative titer usually correlate with disease activity and are used to monitor the effect of treatment. If treatment is successful, the antibody titer gradually declines. A fourfold change in titer (e.g., from 1:16 to 1:4) is necessary to demonstrate a clinically significant difference between two nontreponemal tests. Sequential serologic tests in individuals should be performed by using the same testing method, because quantitative results from the two tests cannot be compared directly; RPR titers are frequently slightly higher than VDRL titers. The timing of follow-up testing is dictated by the clinical presentation and the stage of infection, as well as the HIV status of the refugee, and are detailed in the current treatment guidelines Unlike nontreponemal tests, treponemal tests (e.g., FTA) do not usually revert to nonreactivity after successful treatment of syphilis. Screening with treponemal tests (i.e., use of rapid syphilis tests) is not recommended in high-prevalence settings, because these tests will be reactive in persons with previous successful treatment as well as those with untreated or incompletely treated infection. Therefore, treatment of persons with treponemal positive tests, without previous positive nontreponemal testing (i.e. VDRL, RPR), may result in overtreatment.