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A New Rapid Combination Test for Clostridium difficile Antigen and Toxins A and B in Feces –
Evaluation of the C. DIFF QUIK CHEK COMPLETE™
Authors: M. Goodykoontz, J.T. Boone, D. Link, and D. M. Lyerly1, C. R. Hill2, L. R. Henry2;
TECHLAB®, Inc.
2001 Kraft Drive, Blacksburg, VA, 24060
1TECHLAB, Inc., Blacksburg, VA, 2Carilion Consolidated Laboratories, Roanoke, VA 540-953-1664, [email protected],
[email protected]
ABSTRACT
DISCUSSION
C. difficile causes antibiotic associated diarrhea (AAD) and colitis, with estimates Interpretation of C. DIFF QUIK CHEK COMPLETE™: After the 10 minute incubation period,
The diagnosis of C. difficile disease has become more challenging. More samples are approaching 500,000 cases annually in the U.S. Timely and accurate detection of this the “Ag” reaction was examined for a blue vertical line on the “Ag” side of the Reaction Window, being tested at earlier stages in the disease when levels of antigen and toxin are very opportunistic pathogen is a priority for improved patient healthcare. The gold standard indicating a positive test. If the “Ag” was positive, the “Tox” reaction was examined visually for a low. Many samples are from patients who have already started metronidazole or methods, which include bacterial culture for the organism and tissue culture assay for vertical blue line on the “Tox” side of the Reaction Window, indicating a positive test. A positive vancomycin treatment, which rapidly reduce antigen and toxin levels, possibly affecting toxin, are labor intensive and require 48-72 hours for results. Additionally, the isolation “C” reaction, indicated by a vertical dotted blue line under the “C” portion of the Reaction test performance. In addition to inpatients, many samples are from outpatients and of the organism does not assure that the strain is toxigenic. Recently, an algorithm has Window, confirmed the test performed properly.
nursing home patients, and it still is unclear how diagnostic tests perform in different been proposed to screen specimens for glutamate dehydrogenase (GDH), a marker patient populations. This may be especially confusing with PCR testing, since there are for the organism, with confirmation by toxin testing. The C. DIFF QUIK CHEK Test results:
large numbers of asymptomatic carriers in hospitals and because the presence of the COMPLETE™, a new rapid immunoassay test, utilizes this approach by detecting •Antigen-negative, toxin-negative – C. difficile is not present organism does not always indicate disease.
GDH and toxins A and B in a single device. The C. DIFF QUIK CHEK COMPLETE™ •Antigen-positive, toxin-negative – C. difficile is present test was compared to bacterial culture on cycloserine-cefoxitin-fructose agar and to We developed a new in vitro rapid immunoassay that detects both antigen and toxins •Antigen-positive, toxin-positive – toxin-producing C. difficile is present tissue culture assay using HFF cells. The test was performed according to the package A/B, thus utilizing an algorithm approach to provide the physician with more information •Antigen-negative, toxin-positive – Not observed in our studies insert, with results for antigen, toxins A and B, and an internal dotted control line on the presence of C. difficile and whether it is toxigenic, all in under 30 minutes. Our obtained in under 30 minutes. The study was conducted using samples (n= 460) results showed that the antigen portion of the C. DIFF QUIK CHEK COMPLETE™ assay submitted for routine C. difficile testing at a large hospital with a regional reference correlated well with bacterial culture. In addition, the antigen portion detected >97% of all laboratory. Specimens were from hospital inpatients (57%), nursing home patients tissue culture-positive samples. The toxin portion correlated well with the tissue culture (12%), and outpatients (31%). Patient ages ranged from young children to elderly, assay, and detected typical and atypical toxigenic strains, including the 027 ribotype with the majority of samples from patients >60 years of age. The antigen portion of Negative result
Positive for Antigen only
Positive for Antigen and Toxin
the test exhibited a sensitivity and specificity of 92.1% and 92.5%, respectively, Based on its performance, our results showed that the C. DIFF QUIK CHEK compared to bacterial culture, and detected 97.6% of the samples positive by tissue Performance characteristics: The antigen
BACTERIAL CULT
COMPLETE™ is suitable for use as a stand-alone test and as an accurate screen for culture assay. The toxin portion of the test had a sensitivity and specificity of 85.9% portion of the test exhibited a sensitivity and labs that may consider more time-consuming or expensive tests such as toxigenic culture and 99.5%, respectively, compared to the tissue culture assay.
specificity of 92.1% and 92.5%, respectively, COMPLETE GDH pos 93 27
This is the first commercial test to provide a single assay for the detection of antigen COMPLETE GDH neg
and both toxins A and B. The test is simpler to perform than a stepwise algorithm, offers a rapid turnaround time, and provides more definitive results than single assay CONCLUSIONS
Specificity 92.5% (95% CI 89.1-94.9%)Pred Pos Val 77.5% (95% CI 68.1-84.4%) The C. DIFF QUIK CHEK COMPLETE™ is a rapid immunoassay for the simultaneous detection of C. difficile antigen and toxins A and B in fecal specimens, with results in MATERIALS AND METHODS
TISSUE CULT
Specimens: Four hundred sixty specimens that were submitted to a regional
The antigen portion detected 97.6% of the The test exhibits an excellent correlation with bacterial culture and the tissue culture reference laboratory were included in this study. Specimens were from hospital samples positive by tissue culture assay. COMPLETE GDH pos 83 37
inpatients (57%), nursing home patients (12%), and outpatients (31%). Patient ages COMPLETE GDH neg
ranged from young children to elderly, with the majority of samples from patients the COMPLETE detects the presence of The test is suitable as a stand-alone test for clinical labs and an accurate cost-effective both toxigenic and nontoxigenic strains, screen in labs that pursue additional testing.
whereas tissue culture detects toxigenic Specificity 90.1% (95% CI 86.5-92.9%)Pred Pos Val 69.2% (95% CI 60.0-77.1%) C. DIFF QUIK CHEK COMPLETE™: 750 ul Diluent and 1 drop Conjugate were added to
Excludes >90% of samples from further testing with 99% certainty.
a tube, followed by the addition of 25 ul sample. The contents were mixed well, and 500 ul of the mixture was added to the Sample Well. After 15 minutes at room temp, 300 ul of Wash Solution was added to the Reaction Window, allowed to soak in, and 2 drops of TISSUE CULT
Substrate were added. Reactions were read after 10 minutes.
The toxin portion of the test had a sensitivity COMPLETE TOXIN pos
Tissue culture assay: The tissue culture assay was performed with the TOX-B TEST
COMPLETE TOXIN neg
respectively, compared to the tissue culture using HFF (human foreskin fibroblast) cells.
Sensitivity 85.9% (95% CI 76.2- 92.2%)Specificity 99.5% (95% CI 97.9–99.9%) Bacterial Culture: Bacterial culture was performed using cycloserine-cefoxitin-fructose
agar (CCFA). Cultures were incubated for 72 hours under anaerobic conditions. C. difficile colonies were identified by their typical ground glass appearance on CCFA, and verified using an antigen (GDH) EIA test.

Source: http://www.techlab.com/docs/posters/c_diff_complete_asm2009_1.pdf