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Journal of Clinical Microbiology, September 1999, p. 3044-3047, Vol. 37, No. 9
Microbiology Service, Clinical Pathology
Department, Warren Grant Magnuson Clinical Center, National
Institutes of Health, Bethesda, Maryland 20892,1
and Department of Clinical Pathology, Suburban Hospital,
Bethesda, Maryland 208142
Received 10 February 1999/Returned for modification 29 March
1999/Accepted 25 May 1999
Rapid laboratory diagnosis of Clostridium
difficile-associated diarrhea (CDAD) is highly desirable in the
setting of hospital cost containment. We tested 654 stool specimens to
compare the performance of two assays for rapid detection of toxin A,
the Immunocard Toxin A test (Meridian Diagnostics, Inc.) and the
Culturette Brand Toxin CD enzyme immunoassay (EIA) (Becton Dickinson
Microbiology Systems), with a cytotoxin assay (Cytotoxi Test; Advanced
Clinical Diagnostics) and culture on cycloserine-cefoxitin-fructose
agar followed by determination of the production of toxins A and B. A
chart review was performed for patients whose stool specimens provided
positive results on one to three of the assays. With the "gold
standard" of all four assays positive or chart review evidence of
CDAD, 97 (14.8%) stool specimens were positive by one or more assays
and 557 (85.2%) were negative by all methods. Total agreement for all
assays was 90.5% (592 of 654). The sensitivity, specificity, positive
predictive value, and negative predictive value for toxigenic culture
were 94.7, 98.6, 87.1, and 99.5%, respectively, for toxigenic culture;
87.7, 98.6, 86.2, and 98.8%, respectively, for the cytotoxin assay;
71.9, 99.3, 91.1, and 97.3%, respectively, for the Immunocard; and
68.4, 99.1, 88.6, and 96.9%, respectively, for the Culturette EIA.
While easy to perform and highly specific, these rapid assays do not
appear to be sufficient for accurate diagnosis of CDAD.
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Evaluation of Two Rapid Assays for Detection of
Clostridium difficile Toxin A in Stool Specimens

*
Corresponding author. Mailing address: National
Institutes of Health, Microbiology Service, CPD, Building 10, Room
2C385, 10 Center Dr. MSC 1508, Bethesda, MD 20892-1508. Phone: (301) 496-4433. Fax: (301) 402-1886. E-mail: dfedorko{at}nih.gov.
Present address: MRL Reference Laboratory, Cypress, CA 90630.
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