Commercially-Available Tests: The Xpect C Difficile Test

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Commercially-Available Tests: The Xpect C Difficile Test

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.