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Evaluation of a commercial latex agglutination assay for screening for Clostridium difficile-associated disease
1Washington Hospital, Pennsylvania, USA.
Objective:
To determine if the Clostridium difficile latex agglutination assay is an effective screening procedure for the diagnosis of C. difficile-associated disease (CDAD).
Design:
Convenience sample.
Setting:
The Washington Hospital, a 364-bed, secondary, acute-care center in Washington, Pennsylvania.
Participants:
A total of 321 women and 195 men aged 21 days to 100 years.
Interventions:
Diarrheal stool specimens from patients on antibiotic therapy were randomly tested for the presence of C. difficile-associated antigen by CULTURETTE brand latex agglutination assay (Beckton Dickinson Microbiology Systems, Cockeyesville, MD 21030). Latex-positive samples were confirmed or negated by cytotoxin assay using the Toxi-titer microtiter plate system (Baxter Healthcare Corp., Bartels Diagnostic Division, Issaquah, WA 98027).
Main Outcome Measures:
Comparative statistical analysis of the raw data to develop the sensitivity and specificity of the latex screening assay.
Results:
Stool specimens of 403 patients (78.1%) were negative for C. difficile-associated antigen. Of the latex-positive specimens, 70 (69.3%) were also cytotoxin-positive. Of the indeterminate latex specimens, four (33.3%) were cytotoxin-positive. A total of 70 specimens (13.6%) were positive by both methods and 74 patients (14.3%) were diagnosed with CDAD. Based on this data, the latex agglutination screening assay had a sensitivity of 77.1% and a specificity of 93.4%.
Conclusion:
Latex agglutination for C. difficile-associated antigen is a moderately sensitive screening test for a presumptive diagnosis of CDAD. However, it is not the best screening test for CDAD compared with the new enzyme-linked immunosorbent assay (ELISA) techniques for toxins A and B.