Syphilis (T. pallidum) IgG Antibody Confirmatory EIA
CAPTIA™ Syphilis (T. pallidum)-G is an enzyme immunoassay for the qualitative detection of IgG antibodies to T. pallidum in serum specimens, to be used in conjunction with non-treponemal testing to provide serological evidence of infection with T. pallidum (the agent of syphilis) CAPTIA™ Syphilis (T. pallidum)-G is also intended for testing of serum or plasma specimens to screen blood and/or plasma donors to exclude a history of syphilis.
Syphilis is a disease, usually sexually transmitted, caused by infection with the spirochete Treponema pallidum (T. pallidum). Infection is systemic from the outset and the disease is characterized by periods of latency, often in excess of twenty years. These features, together with the fact that T. pallidum cannot be isolated in culture mean that serological techniques play a major role in the diagnosis of syphilis and treatment follow-up.1
The procedures most commonly used to screen for antibodies to T. pallidum in clinical diagnostic laboratories are based upon their reaction with non-treponemal lipoidal antigens (the reagin tests). Reagin tests, such as the RPR or VDRL, can be used to test serial dilutions of the serum specimen. The end point values from sequentially obtained serum samples decline following successful treatment until after a period of several months the patient will usually become reagin test non-reactive.
Clinical diagnostic serum specimens which are reactive in reagin tests are typically confirmed using treponemal tests such as the Microhaemagglutination-T. pallidum (MHA-TP) or the Fluorescent Treponemal Antibody-Absorption (FTA-ABS) test. In contrast to the non-treponemal tests, treponemal test reactivity will persist following treatment in approximately 85% of the cases often for the life of the patient.2 Any sera giving reactive or equivocal results on initial treponemal based assays must be supplemented with a quantitative non-treponemal test (such as RPR or VDRL) to distinguish from active disease and assist in ruling out false positives.
Donors of blood and/or plasma for transfusion are screened for T. pallidum antibodies using either reagin or treponemal tests. The detection of T. pallidum antibodies is used to help identify donors who present an increased risk of transmitting blood-borne infections.
CAPTIA™ Syphilis-G is a treponemal test for T. pallidum IgG class antibodies.3,4 The enzyme immunoassay format allows use of a microplate reader which eliminates subjective interpretation of results and the test procedure can be automated for high-volume testing.
Microtitration wells coated with T. pallidum antigens are exposed to test specimens which may contain specific antibodies. After an incubation period, unbound components in the test sample are washed away. Specifically-bound IgG reacts with a conjugated horseradish peroxidase (HRP) monoclonal antibody (mAb) during a second incubation period. Following a second wash cycle, specifically-bound enzyme conjugate is detected by reaction with TMB (tetramethylbenzidine). The enzymatic reaction is stopped using 1 N Sulfuric acid. The assay is measured spectrophotometrically to indicate the presence or absence of IgG treponemal antibodies. Test performed by VRL Eurofins, 6933 S. Revere Parkway, Centennial, CO 80112. This test has been cleared or approved for diagnostic use by the U.S. Food and Drug Administration. See package insert for more information.