Enzyme immunoassay (EIA) for toxins A and B: This method is typically used as a rapid test for C diff toxins. Most C diff strains produce both A and B toxins, although some strains may produce only toxin B. Testing for both toxins by EIA gives a higher sensitivity than testing for only toxin B. Although the test can be performed rapidly, rapid EIA tends to have an overall low sensitivity (about 75%) and produces a high false negative rate. To improve upon its sensitivity, the EIA toxin A & B test is often performed in conjunction with the GDH antigen EIA test.
Enzyme Immunoassay (EIA) for GDH antigen: GDH (glutamate dehydrogenase) antigen is an essential enzyme produced by all C diff strains. It is an indicator of active growth of cells and is produced by both toxigenic and nontoxigenic cells. Performing EIA testing for the GDH antigen produced by C diff bacteria cannot distinguish between toxigenic and nontoxigenic strains. Therefore, EIA testing for the GDH antigen is mainly used as an initial screening step and typically requires subsequent testing using more specific assays, such as the EIA for toxins A and B.
The EIA GDH test is considered a rapid assay with good sensitivity capable of accurately ruling out the presence of C diff in stool samples.
