The Xpect® C Difficile Toxin A/B Test, manufactured by Remel of Lenexa, Kansas, is a diagnostic test kit system for the rapid identification of CDI. The test detects C diff toxins A and B in fecal samples.
The following is an overview of the Xpect® C Difficile test:
- The test uses a lateral flow immunochromatographic assay to qualitatively detect the toxins A and B of the C diff bacterium.
- The first step is diluting the stool specimen with a diluent to help solubilize the toxins. A portion of the diluted sample is then mixed with a volume of Conjugate 1 which contains antibodies to toxins A and B coupled to colored blue-black microparticles plus a volume of Conjugate 2 containing biotinylated antibodies to toxins A and B.
- A volume of this mixture is transferred to a test device (cassette) which has immobilized streptavidin as a “test line” and goat anti-immunoglobulin antibody as a “control line.”
- The toxins in the volume of mixture react with the conjugated antibodies to form immunocomplexes as the mixture flows across the test line. The immobilized antibodies react with the color-labeled antigen complex at the test line region producing a visible line. If no antigens (toxins A or B) are present, then the visible line will not appear.
- Excess colored conjugates form a visible band as they cross the control line to document that the test is functioning properly. In this control region, the immobilized antibodies will react with the color-labeled antibodies whether antigen (toxins A or B) is present or not and produce a visible control line.
- The Xpect® test is rapid with test results typically available within 20 minutes. It is simple to use with less than one minute hands-on time.
