Laboratory diagnosis of Clostridium difficile-associated gastrointestinal disease: comparison of a monoclonal antibody enzyme immunoassay for toxins A and B with a monoclonal antibody enzyme immunoassay for toxin A only and two cytotoxicity assays

Abstract

A total of 320 stool specimens obtained from 262 patients suspected of having Clostridium diffciIe-associated gastrointestinal disease were examined with two cytotoxicity assays (CTAs) and two commercially available enzyme immunoassays (EIAs). The CTAs were an in-house-developed procedure (University of Massachusetts Medical Center [UMMC], Worcester, Mass.) and a commercial test (Bartels CTA; Baxter Healthcare Corp., West Sacramento, Calif.). One EIA was a monoclonal antibody-based assay for C. difficile toxins A and B (Cambridge Biotech Corp. [CBCJ, Worcester, Mass.). The other EIA employed monoclonal antibodies directed against only toxin A (Meridian Diagnostics, Cincinnati, Ohio). True-positive and true-negative results were defined on the basis of the results of the four assays, clinical assessments of patients, and the results of other laboratory tests. The sensitivities of the four assays were as follows: Bartels CTA, 100%o; UMMC CTA, 97.2%; CBC EIA, 84.5%; and Meridian EIA, 69.0%o. The Bartels CTA demonstrated a specificity of 99.2%. The other three assays had a specificity of 100%o.

European Society of Clinical Microbiology and Infectious Diseases (ESCMID): Data review and recommendations for diagnosing Clostridium difficile-infection (CDI)

“…Of the 71 potentially relevant papers retrieved for more detailed assessment, 28 were excluded from further analysis: 15 studies investigated tests that were no longer commercially available; three studies did not test all samples with the reference test; three studies used an inappropriate reference standard; two studies comprised non‐clinical human stool samples; two studies did not report sufficient information to allow us to calculate sensitivity and specificity; one study using CCA did not report if neutralization of the cytopathic effect was executed; and for two studies, full text articles were not available. Therefore, a total of 43 studies was included in this systematic review [6–10,12–15,21–23,23–54].…”

“…Repeated testing of samples with an initial intermediate result was performed in nine studies. Of these, eight studies reported results only after repeated testing [31,33,43–46,53,54] and one study reported the results of both initial and repeated testing [48]. In one study, samples with intermediate results after repeated testing were called negative [53].…”

Rapid detection of Clostridium difficile toxin A in stool specimens

“…They can be performed in approximately 2 h and have generally shown good specificity. Nevertheless, their sensitivity varies from 53% to 100% according to different studies [9–11,13–18], with discrepancies explained by the criteria used for the diagnosis of CDAD. In the present study, the sensitivity of the ToxA test was estimated to be 77.4%, which is lower than the 84.6% reported by Schué et al [16] using the the same clinical criteria for diagnosis of CDAD.…”

“…Laboratory diagnosis relies on culture of the microorganism and/or detection of the toxins in stool specimens [8]. Many immunoenzymatic assays that detect either toxin A or toxins A+B have become commercially available in the 5 last years [9–18]. They represent good alternatives to cytotoxicity assays for laboratories without cell‐culture facilities.…”

Pathophysiology, Diagnosis and Treatment of Clostridium difficile Infection.

“…Neutralization of cell rounding by using specific anti-toxin B sera confers specificity to the assay. 34 The test is generally reported as positive or negative, as there is no direct correlation between toxin B levels in the stool and severity of the disease. Stool culture for C. difficile is a less specific method for establishing a diagnosis, since non-toxigenic strains of C. difficile can also be isolated with this approach.…”