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Journal of Clinical Microbiology, January 1998, p. 184-190, Vol. 36, No. 1
TechLab, Inc., Corporate Research Center,
Blacksburg, Virginia 240601;
Anaerobe
Laboratory, Indiana University Hospital, Indianapolis, Indiana
462022;
Clinical Pathology, Hershey
Medical Center, Hershey, Pennsylvania
170333;
Department of Microbiology,
PinnacleHealth System, Harrisburg, Pennsylvania
17105-87004; and
Department of Medical
and Research Technology, School of Medicine, University of
Maryland, Baltimore, Maryland 21201-10825
Received 3 July 1997/Returned for modification 8 September
1997/Accepted 8 October 1997
Clostridium difficile, the primary cause of nosocomial
diarrhea in the United States and many other industrialized countries, is recognized as a major health concern because of its ability to cause
severe intestinal disease leading to complications such as relapses and
infections due to vancomycin-resistant enterococci. The disease results
from two toxins, toxins A and B, produced by this pathogen. In this
study, we evaluated the TOX A/B TEST, a new 1-h enzyme immunoassay
(EIA) that detects toxins A and B. We compared the test with the tissue
culture assay, which is recognized as the "gold standard" for
C. difficile testing. Evaluations were performed
in-house at TechLab, Inc. (Blacksburg, Va.) and off-site at four
clinical laboratories. Of 1,152 specimens tested, 165 were positive by
the TOX A/B TEST and tissue culture and 973 were negative by both
tests. The sensitivity and specificity were 92.2 and 100%,
respectively. The positive and negative predictive values were 100 and
98.6%, respectively, and the correlation of the TOX A/B TEST with
tissue culture was 98.8%. When discrepant samples were resolved by
culture, the sensitivity and specificity were 93.2 and 98.9%,
respectively. The positive and negative predictive values were 100 and
98.8%, respectively, with a correlation of 99.0%. There were no
specimens that were positive by the TOX A/B TEST and negative by tissue
culture. Fourteen specimens were negative by the TOX A/B TEST but
positive by tissue culture. Of these, two were negative by toxigenic
culture, five were positive by toxigenic culture, and seven were not
available for further testing. There were no indeterminate results,
since the test does not have an indeterminant zone. In a separate
study, 102 specimens that were positive by tissue culture and the TOX
A/B TEST were examined in toxin A-specific EIAs. Two specimens that
presumptively contained toxin A-negative, toxin B-positive
(toxA
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Multicenter Evaluation of the Clostridium difficile
TOX A/B TEST
/toxB+) isolates were identified. One specimen was from a
patient with a clinical history consistent with C. difficile infection. Isolates obtained from these specimens by
selective culture on solid media and in broth tested
toxA
/toxB+ when grown in brain heart infusion dialysis flasks,
which stimulate in vitro production of both toxins. Our findings show
that the TOX A/B TEST is suitable as a diagnostic aid for C. difficile disease because it correlates well with tissue culture
and detects isolates that may be missed with toxin A-specific EIAs.
*
Corresponding author. Mailing address: TechLab, Inc.,
1861 Pratt Dr., Corporate Research Center, Blacksburg, VA 24060. Phone: (540) 231-3943. Fax: (540) 231-3942. E-mail:
techlab{at}bev.net.
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