Comparison of Immuno Card Toxins A&B and the New Semiautomated Vidas Clostridium difficile Toxin A&B Tests for Diagnosis of C. difficile Infection

Abstract

ᰔWe recently showed the ImmunoCard Toxins A&B test (ImmunoCard) (Meridian) to be as specific as and more sensitive than two widely used immunochromatographic tests to diagnose Clostridium difficile infection (CDI) (1). The Vidas C. difficile Toxin A&B test (Vidas-AB) (bioMérieux) is a new enzyme-linked fluorescent immunoassay (ELFA) that detects toxins A and B. As it is automated, it reduces the workload compared to traditional enzyme-linked immunosorbent assays. Our objectives were to evaluate the performance of Vidas-AB and to compare it with that of ImmunoCard for the diagnosis of CDI in stool specimens.(This study was presented at the 48th Interscience Conference on Antimicrobial Agents and Chemotherapy [ICAAC], Washington, DC, 25 to 28 October 2008.) The combination of the direct cytotoxicity assay from stool specimens and the cytotoxicity assay from isolates was considered the gold standard, so a true positive result was defined as positive by direct cytotoxicity assay or negative by direct cytotoxicity assay and positive by cytotoxic culture (1-3). ImmunoCard and Vidas-AB were performed according to the manufacturers' instructions. Due to the relatively long test time of Vidas-AB, a one-test-per-sample approach was adopted, and the equivocal values obtained with Vidas-AB were considered negative results.During the study period, a total of 487 stool specimens from 412 patients were tested. Toxigenic C. difficile was detected using the gold standard in 62 stool specimens (12.7%) from 53 patients. The sensitivity of the direct cytotoxicity assay was 69.4%. The greater specificity of Vidas-AB compared with that of ImmunoCard was statistically significant (P ϭ 0.019), although there were no statistically significant differences between sensitivities and predictive values (Table 1). Vidas-AB gave 13 equivocal results (2.7% of all results). These were for 2 specimens with toxigenic C. difficile and 11 specimens with negative results. ImmunoCard was the quickest technique: the median time to test 5 stool specimens was 24 min and 10 s using ImmunoCard, whereas Vidas-AB took 80 min and 25 s (P Ͻ 0.0001; twotailed Wilcoxon test for paired samples). The hands-on times for both methods were very similar.To our knowledge, two groups have published evaluations of Vidas-AB (4-6, 8). In the most complete evaluation of Vidas-AB in the three papers published by Shin et al., the sensitivity (63.3%) and specificity (96.7%) values (compared with toxigenic culture and PCR results for tcdA and tcdB as standards) were similar to those obtained in our study (4-6). Terhes et al. (8) compared Vidas-AB with the BD GeneOhm Cdiff assay, a real-time PCR test based on the detection of the tcdB gene of C. difficile, and achieved sensitivity and specificity values for Vidas-AB of 34.5% and 98.5%, respectively. Only two studies have evaluated ImmunoCard using toxigenic culture with or without the cytotoxicity assay as the gold standard (1, 7). In the previous evaluation of ImmunoCard performed in our laboratory (1), the sensitivity (66.7%...

Outcomes and Risk Factors Associated withClostridium difficileDiarrhea in Hospitalized Adult Patients

“…Selection bias is always a possibility in case-control studies, because the selection of controls is often challenging. We used a diagnostic tool with high specificity (98%) and only moderate sensitivity (69.4%) for CDI [ 14 ]; consequently, it is probable that our sample failed to include less severe cases of CDI. Nevertheless, our strategy of selecting appropriate controls with non- C. difficile -related hospital-acquired diarrhea and matching them to our study subjects was designed to minimize the possibility of selection bias by ensuring that the distributions of possible confounders did not differ substantially between cases and controls [ 25 ].…”

“…In this study, all samples of stool in the hospital's microbiology laboratory electronic database between January 2010 and July 2012 were identified. These samples were analyzed for the presence of toxins A and B of C. difficile using an enzyme-linked fluorescent immunoassay (Vidas A & B, BioMérieux, Durham, NC, USA) [ 14 ] according to the manufacturer's instructions.…”

Recommendations for the diagnosis and treatment of Clostridioides difficile infection: An official clinical practice guideline of the Spanish Society of Chemotherapy (SEQ), Spaish Society of Internal Medicine (SEMI) and the working group of Postoperative Infection of the Spanish Society of Anesthesia and Reanimation (SEDAR)

“…At first, laboratories used EIAs that detected only toxin A but, with the dissemination and higher frequency of strains toxin A-/toxin B+ producing CDI, these were replaced by EIAs capable of detecting both toxins [80][81][82][83]. Some comparative studies have shown that EIAs have sensitivity values of 40-60% when compared with toxigenic cultures [84][85][86][87][88][89][90]. On the other hand, the specificity of most of these tests is higher than 90%.…”

Diagnostic yield of repeat sampling with immunoassay, real-time PCR, and toxigenic culture for the detection of toxigenic Clostridium difficile in an epidemic and a non-epidemic setting

“…Immunoassays are directed to either an enzyme carried by C. difficile (glutamate dehydrogenase) or toxins produced by C. difficile (TcdA and TcdB). These immunoassays are more rapid diagnostic tests, but it is well known that direct immunoassay testing of stool samples lacks adequate sensitivity for the detection of toxigenic C. difficile , with a sensitivity of 60–70 % [ 1 – 3 ]. Real-time polymerase chain reaction (PCR)-based diagnosis has proved to be highly sensitive and has become more widely available [ 1 , 4 ].…”