Commercially-Available Tests: Overview

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Commercially-Available Tests: Overview

Many in vitro diagnostic tests are currently available commercially to identify CDI. Many of these commercial tests tend to detect three types of analytes: 1) the genes for toxins A and B (tcdB and tcdA); 2) the GDH antigen, a metabolic enzyme produced in high amounts by actively growing C diff organisms; and 3) toxins A and B, which cause CDI. Unfortunately, not all of these commercial tests perform equally well. There can be differences in purity, specificity, and affinity for the C diff antigens or toxins. In addition, and as previously indicated, using fecal specimens can be challenging because of the stability and impurities existing with these specimens.

Most health care facilities seek to detect CDI as early as possible so that treatment and other measures can be quickly initiated. Therefore, the emphasis on using commercially-available testing for CDI currently favors the employment of a rapid, technologically simple, and low-cost assay. There are a number of such tests commercially available, especially EIA’s for C diff toxins A and B, as well as the GDH antigen. In the following sections, this course will review two such tests; the XpectTM C Difficile Toxin A/B test and the C Diff Quik Chek Complete® test.