Intended Use

TREP-SURE™ EIA is a qualitative enzyme immunoassay for the in vitro diagnostic detection of Treponema pallidum (syphilis) antibodies in human serum or EDTA and citrated plasma. This product can be used as an initial screening test or as a confirmatory diagnostic test, but is not cleared (approved) by the U.S. Food and Drug Administration (FDA) for use in screening blood or plasma donors.

Warning: A positive result is not useful for establishing a diagnosis of syphilis. In most situations, such a result may reflect a prior treated infection; a negative result can exclude a diagnosis of syphilis except for incubating or early primary disease.

Summary and Explanation

In response to Treponema pallidum subsp. pallidum, the causative agent of syphilis, two types of antibody responses normally result: non-specific (anti-cardiolipin) and specific (anti-treponemal). While non-specific antibodies occur in the majority of infectees, many other conditions can give rise to false positive results, yielding an overall specificity of about 50% in the general population.

One of the major reasons for the continued use of non-specific tests (RPR, VDRL, and Wasserman etc.) is based on the observation that in response to appropriate (antibiotic) treatment, a significant decrease in titer usually takes place, which is taken as the criterion of adequate treatment.

Treponemal specific tests are based on the use of treponemal antigens in the assay. Prior to the HIV era, treponemal tests were largely used to confirm positive results obtained by non-specific screen tests. Although older treponemal tests (such as MHA-TP and FTA-Abs) are generally considered reliable for past and current infection (regardless of treatment), their specificity is limited due to the presence of non-specific antigens in preparations of in vivo cultivated T. pallidum. The use of recombinant treponemal antigens in TREP-SURE™ results in increased sensitivity and specificity. Unless applied during early primary syphilis, treatment does not significantly affect the treponemal antibody status; hence no assumptions about efficacy of treatment or staging of disease can be made.

The assay methods described above all require visual interpretation and are limited to subjective interpretation by the operator. The use of the more specific Enzyme ImmunoAssay (EIA) has received wide spread acceptance due to the colorimetric results in a 96 well microplate format that can be automated and read photometrically. The TREP-SURE™ Syphilis EIA assay uses recombinant antigens in an enzyme immunoassay format to yield a more specific result with objective reading of absorbencies compared to a Cut-off Calibrator.

Principle of the Test

Specific recombinant treponemal antigens are immobilized on the microplate wells. Patient samples and controls are added to the wells. Anti-treponemal antibodies, if present in the patient's serum or plasma, will specifically bind to the immobilized antigens; all non-bound proteins are removed during the washing step. The antigen-antibody complex is subsequently reacted with Horseradish Peroxidase (HRPO) conjugated treponemal antigens. After a second wash, which removes the unbound conjugates, a chromogenic reaction takes place on the plate as a result of addition of TMB, a substrate for the peroxidase. The resulting color is measured spectrophotometrically (450 nm) after adding stop solution. Color intensity is proportional to the amount of antibody present in the patient's sample.

Please refer to the complete Package Insert for more information.