Rapid detection of Clostridium difficile toxin A in stool specimens

107

The laboratory diagnosis of Clostridium difficile-associated disease (CDAD) is based on culture and toxin detection in fecal specimens. Culture is performed on a commercially available selective media. C. difficile colony morphology is typical when viewed under a dissecting microscope. Definitive identification is best obtained by gas liquid chromatography. Culture is very sensitive but, when used alone without toxin testing, it leads to low specificity and misdiagnosis of CDAD when high rates of asymptomatic carriage exist. Toxin detection by a tissue culture cytotoxin assay followed by neutralisation with specific antiserum is often considered the standard. However, this approach lacks sensitivity and has not detected up to 30% of patients with confirmed CDAD. Multiple enzyme immunoassays (EIAs) have been introduced by various manufacturers for the detection of toxin A alone or for both toxins A and B. Some of these are designed to give results in less than 1 h. Comparative studies of EIA kits reported that the sensitivity and specificity are slightly lower than cytotoxin assays. Toxigenic culture tests C. difficile isolates for toxin production: colonies isolated on selective media are tested for in-vitro toxin production either by a cytotoxicity assay or by direct EIA. It has higher sensitivity than the cytotoxicity assay and equivalent specificity. In the routine laboratory, culture and toxin detection should be performed on every specimen and, in culture-positive and fecal toxin-negative cases, toxigenic cultures should be performed on isolated colonies.

Section: Toxin Detectionsupporting

confidence: 75%

Laboratory diagnosis of Clostridium difficile disease

Delmée

2001

107

“…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].…”

Section: Resultsmentioning

confidence: 99%

“…Intermediate test results (i.e. not interpretable, difficult to interpret, invalid or weak positive results) were reported in 17/43 studies (40%), including four membrane‐type EIAs (six studies using the Triage assay [13,14,30,31], the ColorPac Toxin A assay [31], and/or the Immunocard C. difficile assay [39,54]). Repeated testing of samples with an initial intermediate result was performed in nine studies.…”

Section: Resultsmentioning

confidence: 99%

“…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].…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

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

Crobach

Dekkers

Wilcox

et al. 2009

366

298

The aim of the present systematic review was to evaluate the available evidence on laboratory diagnosis of CDI and to formulate recommendations to optimize CDI testing. In comparison with cell culture cytotoxicity assay (CCA) and toxigenic culture (TC) of stools, we analyzed the test characteristics of 13 commercial available enzyme immunoasssays (EIA) detecting toxins A and/or B, 4 EIAs detecting Clostridium difficile glutamate dehydrogenase (GDH), and a real-time PCR for C. difficile toxin B gene. In comparison with CCA and TCA and assuming a prevalence of CDI of 5%, PPV and NPV varied between 0.28-0.77, 0.12-0.65 and 0.98-1.00, 0.97-1.00, respectively. Only if the tests were performed in a population with a CDI prevalence of 50 percent, would PPVs be acceptable (ranging from 0.71 to 1.00).To overcome the problem of a low PPV, we propose a two step approach, with a second test or a reference method in case of a positive first test. Further reducing the number of false negative results would require either retesting of all subjects with a negative first test, or re-testing all subjects with a negative second test, after an initially positive test. This approach resulted in non-significant improvements, and emphasizes the need for better diagnostic tests. Further studies to validate the applicability of two-step testing, including assessment of clinical features, are required.

“…These tests include faecal culture on selective media, detection of a nonspecific antigen (glutamate dehydrogenase, GDH) and direct detection of toxins A and/or B from stools. This latter method can be performed either by the cytotoxicity assay or by a direct enzyme immunoassay (EIA) [11–22]. The cytotoxicity assay is considered by many authors as the standard because of its great sensitivity for the detection of toxin B [23].…”

Section: Introductionmentioning

confidence: 99%

A European survey of diagnostic methods and testing protocols for Clostridium difficile

Barbut

Delmée

Brazier

et al. 2003

106

The results of this study suggest marked discrepancies between laboratories and also between countries regarding the criteria by which C. difficile is investigated for, and the methods and the strategies that are used for the diagnosis of C. difficile. These discrepancies could be explained by the lack of clear guidelines for C. difficile diagnosis in each country, and by the importance that physicians attach to C. difficile. Precise guidelines for C. difficile diagnosis would be the first step to make possible accurate comparison of the incidence and the epidemiology of CDAD from one hospital to another or from one country to another.