BacteriologyPerformance of TechLab C. DIFF QUIK CHEK™ and TechLab C. DIFFICILE TOX A/B II™ for the detection of Clostridium difficile in stool samples
Introduction
Clostridium difficile was first identified as the primary cause of pseudomembranous colitis in 1978. Since then, the organism is recognized as the leading cause of hospital-acquired diarrhea called C. difficile-associated diarrhea (CDAD).
In the United States alone, the estimated number of cases of CDAD exceeds 250 000 per year, causing an economic burden of over $1 billion to the health care system annually (Wilkins and Lyerle, 2003, Kyne et al., 2002). Previously, reports of C. difficile outbreaks have been restricted to a single hospital. Recently, however, there appears to be a wider distribution with increased mortality. Consequently, in some parts, the disease has become a serious public health concern. In one Canadian hospital, the incidence of C. difficile cases increased from 35.6 per 100 000 population in 1991 to 156.3 per 100 000 in 2003. In the same period, the proportion of complicated cases increased from 7.1% to 18.2% and 30 days mortality rate from 4.7% to 13.8% (Pėpin et al., 2004).
The diagnosis of C. difficile is based upon the clinical history of recent antibiotic use, diarrhea, and laboratory tests for C. difficile markers including isolation of C. difficile, determination of the presence of glutamate dehydrogenase (GDH), and toxins. TechLab, Blacksburg, VA, has recently marketed 2 membrane-bound enzyme immunoassays (EIAs), C. DIFF Quick CHEK (QC-GDH) and TOX A/B Quick CHEK (QC-toxinA/B), that detect GDH and toxins A/B, respectively.
The aim of this study was to evaluate and compare the 2TechLab assays (QC-toxinA/B and QC-GDH) with the Triage® C. difficile Panel membrane-bound immunoassay (Biosite Diagnostics, San Diego, CA), the culture isolation ofC. difficile from stool samples, and an in-house cytotoxin assay (CTA). The Triage® C. difficile Panel assay containsdetection zones for GDH (TR-GDH) and toxin A (TR-toxinA).
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Study protocol
All nonformed stools submitted from inpatients suspected of CDAD were included in the study. All tests (culture isolation, QC-toxinA/B, QC-GDH, TR-GDH, and TR-toxinA) were performed within 24 h of the arrival of specimens in the laboratory. A portion of the stool was frozen at −70 °C for further investigation if required. Samples positive for GDH or culture but negative for the presence of toxin/s by TR-toxinA and QC-toxinA/B were further tested by CTA. Also, samples on Triage panels that were
Statistical analysis
For the purpose of this study, the gold standard was considered a combination of several test results indicating a diagnostic positive for toxigenic C. difficile. A sample that was positive for either of the 2 screening methods (culture or GDH) and positive for toxin (toxin A, toxin A/B, or cytotoxic assay) was considered to be true positive for toxigenic C. difficile. This gold standard was used to calculate the sensitivities and specificities of the membrane-bound immunoassay tests. The
Assay results
In total, 401 specimens were processed during the study. All specimens were tested by the TechLab and Triage immunoassays and culture. Ten (2.5%) of 401 specimens could not be evaluated by the Triage® C. difficile panels because of discoloration of panels. Cytotoxic assay was performed on 54 specimens. Thirteen samples were excluded when analyzing performance of toxin assays because CTA was not performed in the face of positive culture or GDH but negative toxin immunoassay. For most of these
Discussion
At present, there is no sufficiently discriminatory or specific screening test for the diagnosis of CDAD; consequently, the Society for Healthcare Epidemiology of America has recommended that culture as well as a cytotoxic assay should be performed on stool specimens submitted for determination of CDAD (Gerding et al., 1995). The approach is problematic because both culture and CTA have slow turnaround times and require a minimum of 2 days to yield results.
Although CTA is the most sensitive
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Cited by (24)
Diagnostic Pitfalls in Clostridium difficile Infection
2015, Infectious Disease Clinics of North AmericaCitation Excerpt :As some C difficile strains do not produce toxin A, it is recommended that toxin immunoassays should detect both toxins A and B. Feces specimens may be kept at 4°C for days or weeks before being assayed for toxin, but freeze-thawing of samples reduces the sensitivity of these tests.55 Test sensitivities in earlier studies were reported to be 69% to 99%, with specificities of 94% to 100%,56–64 although these were relatively small (typically <500 samples). Recent reports have claimed sensitivities of toxEIAs to be less than 60%,65 although these studies compared EIA with CC.
Laboratory diagnosis of Clostridium difficile infection: Can molecular amplification methods move us out of uncertainty?
2011, Journal of Molecular DiagnosticsLack of effect of strain type on detection of toxigenic Clostridium difficile by glutamate dehydrogenase and polymerase chain reaction
2011, Diagnostic Microbiology and Infectious DiseaseThe role of glutamate dehydrogenase for the detection of Clostridium difficile in faecal samples: A meta-analysis
2011, Journal of Hospital InfectionStool Studies: Tried, True, and New
2010, Critical Care Nursing Clinics of North AmericaCitation Excerpt :The recommendation for conduction of three serial EIA tests when the initial test is positive has been shown to increase accuracy of detection by 10%.14 Use of anaerobic culture, real-time polymerase chain reaction, and common antigen testing can detect the presence of the organism but are incapable of identifying the difference between toxin- and nontoxin-producing strain.20 Real-time polymerase chain reaction tests allow for detection and quantification of the organism and, therefore, have higher sensitivity than the EIA and produce rapid results.
European Society of Clinical Microbiology and Infectious Diseases (ESCMID): Data review and recommendations for diagnosing Clostridium difficile-infection (CDI)
2009, Clinical Microbiology and InfectionCitation Excerpt :Blinding of investigators was reported in 12/43 studies. 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.