Evaluation of Methods for Detection of Toxins in Specimens of Feces Submitted for Diagnosis of Clostridium difficile - Associated Diarrhea

Abstract

Clostridium difficile is the principal pathogen associated with hospital-acquired acute diarrheal disease. We have evaluated the performances of six approaches for diagnosis of C. difficile-associated diarrhea (CDAD). Consecutive stool specimens (n ‫؍‬ 200) from 133 patients were examined by cytotoxin assay, by culture of C. difficile on cycloserine-cefoxitin-fructose agar, and by toxin detection using four rapid immunoassay systems (Oxoid Toxin A test, ImmunoCard Toxin A test, TechLab Tox A/B II test, and Premier Toxins A&B test). A diagnosis of CDAD was established for 35 (27%) patients (representing 29% of specimens). The adjusted sensitivity and specificity of the methods were, respectively, 98 and 99% for the cytotoxin assay, 54 and 99% for ImmunoCard, 50 and 98% for Oxoid, 79 and 98% for TechLab, 80 and 98% for Premier, and 57 and 100% for culture. The TechLab and Premier assays are acceptable tests for diagnosis of CDAD but are not equivalent to the cytotoxin assay.Nosocomial infection with Clostridium difficile increases morbidity and mortality among hospitalized patients and places a significant economic burden on health services (3,7,18). Early diagnosis is associated with better prognosis (12); therefore; rapid laboratory diagnosis is highly desirable.The diagnosis of C. difficile-associated diarrhea (CDAD) is usually based on clinical features and detection of C. difficile toxin. Tissue culture assay is considered the "gold standard" for the demonstration of C. difficile toxins in specimens of feces. The technical complexity, slow turnaround time (24 to 48 h), and lack of standardization of the cytotoxin assay are significant limiting factors (11). As a result, a number of commercial products for rapid immunological detection of toxin have been developed. Some products are based on detection of only C. difficile toxin A, while others detect both toxin A and toxin B. The practical importance of detection of both toxins is unclear (4, 7). The impetus to detect both toxins may be supported if the suggestion that toxin A Ϫ B ϩ strains of C. difficile are emerging as significant pathogens is validated (1, 13).In this study, four rapid immunoassays were evaluated for the detection of C. difficile toxins in stool specimens and their performances were compared with that of the cytotoxin assay. The rapid assays consisted of two microwell-based enzyme immunoassays that detected both toxin A and toxin B and two chromatographic cassette-based immunoassays that detected toxin A only. The performances of six assay methods (the four immunoassays, the cytotoxin assay, and bacteriological culture) were evaluated with reference to clinical and biological criteria for diagnosis of CDAD. MATERIALS AND METHODSTwo hundred consecutive stool specimens (from 133 adult patients) received in the laboratory for routine investigation of C. difficile infection were included in the study. Stool specimens were cultured on the day of receipt. The study included specimens that were transported by routine road transport at room temper...

A comparison of Clostridium difficile diagnostic methods for identification of local strains in a South African centre

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A Superior Test for Diagnosis of Clostridium difficile-Associated Diarrhea in Resource-Limited Settings

“…The reported prevalence of CDI differs across hospitals and depends on detection methods (3). In Thailand, the reported prevalence of Clostridium difficile-associated diarrhea (CDAD) has varied from 5z to 25z (4)(5)(6)(7).…”

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