With its latest rapid test, R-Biopharm is now able to offer a complete solution for the immunological diagnosis of Clostridium difficile in compliance with the new international guidelines of various professional societies (ESCMID, SHEA/ISDA).
The currently recommended two-step algorithm can be consistently used, regardless of whether testing a large series of samples by ELISA or small series of samples or single samples using a rapid test. In the first step, the very sensitive test for Clostridium difficile-specific glutamate dehydrogenase (GDH) determines whether patients with clinical suspicion of Clostridium difficile infection (CDI) require additional testing. This is the case only if the specific GDH test is positive. Statistically and depending on prevalence, the test is positive in only about 15 to 35 % of test samples from patients with suspected CDI. Therefore, 65 to 85 % of all samples tested by this method are GDH-negative, so CDI can be excluded with high probability. The negative predictive value of the GDH assay is 98 to 100 percent. Asymptomatic carriers have very low levels of Clostridium difficile and, thus, very low levels of GDH. These very low levels have no clinical significance unless there is a risk that the spores might be transferred via the fecal-oral route to immunocompromise patients or to hospital or nursing home patients undergoing antibiotic therapy.
If the GDH test is positive, Clostridium difficile toxins A and/or B must be detected which, in accordance with the guidelines, proves the presence of C. difficile infection. Detection of the toxin genes by PCR alone is not conclusive but merely indicative. The gold standard assays for detection of C. difficile toxins are the cytotoxin assay (CTA) and toxigenic culture, which require initial 48-hour culture enrichment of C. difficile from stool samples. In both cases, a filtrate of stool sample (CTA) or a culture filtrate is added to the toxin-sensitive cell culture and observed for about 1 to 2 days for any typical pathogenic effects (TPE) that might occur. Both methods are very time-consuming and poorly standardized and are therefore used by only a few laboratories.
It is easier and faster to detect C. difficile toxins immunologically using an ELISA kit (such as RIDASCREEN®Clostridium difficile Toxin A/B) or an appropriate rapid test (such as RIDA®QUICK Clostridium difficile Toxin A/B).