1089. Analytical Performance of an Ultrasensitive Immunoassay for Detection of Clostridium difficile Toxins in Stool
Session: Poster Abstract Session: Diarrhea Diagnostic Dilemmas
Friday, October 5, 2018
Room: S Poster Hall
  • 1089_IDWPOSTER.pdf (359.2 kB)
  • Background: Clostridium difficile infection (CDI) is the main cause for nosocomial diarrhea. Currently available assays for the diagnosis of CDI show deficits in sensitivity, specificity, and/or turnaround time. The Singulex Clarity® C. diff toxins A/B assay, in development for the Singulex Clarity® system, was designed to provide an accurate and automated detection of C. difficile toxins A (TcdA) and B (TcdB) in stool. Here, the analytical performance of the assay is reported.

    Methods: Limits of detection (LoD) for TcdA and TcdB in stool and buffer was determined, and a preliminary cutoff, as compared to cell cytotoxicity neutralization assay (CCNA), was established. Analytical reactivity against 38 toxigenic and non-toxigenic C. difficile strains of eight different toxinotypes was determined. Cross-reactivity against 53 other gastrointestinal pathogens and potential interference by 11 endogenous and exogenous substances were determined. Reproducibility was tested with triplicate samples (n=85), and stability was evaluated in samples stored at room temperature, refrigerated, and frozen conditions, and subjected to three freeze-thaw cycles.

    Results: The LoDs for TcdA and TcdB were 0.8 and 0.3 pg/mL in buffer, and 2.0 and 0.7 pg/mL in stool, respectively. Using a preliminary cutoff, the assay demonstrated 96.3% sensitivity and 96.1% specificity compared to CCNA. The Singulex Clarity® C. diff toxins A/B assay detected toxins from all tested strains and toxinotypes. No cross-reactivity or interference were detected. The repeatability was 99%, and samples for C. difficile toxin testing were stable up to eight hours in room temperature, one week in 2–8 °C, six months in -70 °C, and up to three freeze-thaw cycles.

    Conclusion: The Singulex Clarity C. diff toxins A/B assay (in development), can detect TcdA and TcdB at very low concentrations and it has high sensitivity and specificity compared to CCNA. The assay demonstrates reactivity to common C. difficile strains, does not show cross-reactivity to common gastrointestinal pathogens, is robust against common interferents, allows for toxin detection in both fresh and frozen stool samples and up to three freeze-thaw cycles, and provides results with high reproducibility.

    Amelita Bartolome, PhD, Anna Almazan, BS, Salina Abusali, MS, Stanley Tam, MS, Eric Lee, BS, Amogh Changavi, BS, Wendy Trinh, BS, Kent Chau, BS, Joel Estis, MS, Brian Noland, PhD and Jeffrey Bishop, PhD, Singulex, Inc., Alameda, CA


    A. Bartolome, Singulex, Inc.: Employee , Salary .

    A. Almazan, Singulex, Inc.: Employee , Salary .

    S. Abusali, Singulex, Inc.: Employee , Salary .

    S. Tam, Singulex, Inc.: Employee , Salary .

    E. Lee, Singulex, Inc.: Employee , Salary .

    A. Changavi, Singulex, Inc.: Employee , Salary .

    W. Trinh, Singulex, Inc.: Employee , Salary .

    K. Chau, Singulex, Inc.: Employee , Salary .

    J. Estis, Singulex, Inc.: Employee , Salary .

    B. Noland, Singulex, Inc.: Employee , Salary .

    J. Bishop, Singulex, Inc.: Employee , Salary .

    Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 3rd with the exception of research findings presented at the IDWeek press conferences.