1088. Ultrasensitive Detection of C. difficile Toxins in Stool Using Single Molecule Counting Technology: A Multicenter Study for Evaluation of Clinical Performance
Session: Poster Abstract Session: Diarrhea Diagnostic Dilemmas
Friday, October 5, 2018
Room: S Poster Hall
Background: Commercially available tests for Clostridium difficile infection (CDI) make test selection by the laboratory difficult due to the following unsatisfactory characteristics: long turnaround time, poor sensitivity, and/or poor specificity. The Singulex Clarity® C. diff toxins A/B assay (in development) is a rapid and automated immunoassay for the detection of C. difficile toxins A and B in stool, with analytical limits of detection for toxins A and B at 2.0 and 0.7 pg/mL, respectively. In this multicenter study, the clinical performance of the Singulex Clarity C. diff toxins A/B assay was compared to standalone PCR, a multistep algorithm with enzyme immunoassay (EIA) and PCR, and cell cytotoxicity neutralization assay (CCNA).

Methods: Fresh samples from 267 subjects with suspected CDI were tested at two sites (Minneapolis Medical Research Foundation and TriCore Reference Laboratories) with the Singulex Clarity assay, PCR (Xpert® C. difficile), and EIA (C. Diff Quik Chek Complete®) for GDH and toxin testing. The performance of the assays and multistep algorithms were evaluated against CCNA (Microbiology Specialists, Inc.).

Results: The overall CDI prevalence was 15.7%. The Singulex Clarity C. diff toxins A/B assay had 90.5% sensitivity and 96.0% specificity, with a 98.2% negative predictive value when compared to CCNA, and the Clarity assay’s AuROC was 0.9534. PCR had 90.5% sensitivity and 91.1% specificity. Compared to CCNA, the toxin EIA had 47.6% sensitivity and 100% specificity. Testing with a multistep algorithm using EIA with discordant results reflexed to PCR resulted in 85.7% sensitivity and 94.7% specificity.

Conclusion: The ultrasensitive Singulex Clarity C. diff toxins A/B assay is equivalent to the sensitivity of PCR while providing higher specificity. Compared to a multistep algorithm, the Clarity assay provides higher sensitivity and specificity while providing faster time-to-result in a simpler-to-understand, one-step reporting structure, allowing for a standalone, single-step solution for detection of C. difficile toxins in patients with suspected CDI.

Stephen Young, Ph.D. , D(ABMM)1, Ray Mills, BS2, Christen Griego-Fullbright, BS(ASCP)2, Aaron Wagner, MS2, Emily Herding, MS3, Vickie Nordberg, MS4, Emily Friedland, PhD5, Amelita Bartolome, PhD5, Anna Almazan, BS5, Stanley Tam, MS5, Sheryl Biscocho, MS5, Salina Abusali, MS5, Johanna Sandlund, MD, PhD5, Joel Estis, MS5, Jeffrey Bishop, PhD5 and Glen Hansen, PhD4, (1)Research and Clinical Trials, TriCore Reference Laboratories, Albuquerque, NM, (2)TriCore Reference Laboratories, Albuquerque, NM, (3)Minneapolis Medical Research Foundation, Hennepin County Medical Center, Minneapolis, MN, (4)Microbiology, Hennepin County Medical Center, Minneapolis, MN, (5)Singulex, Inc., Alameda, CA

Disclosures:

S. Young, None

R. Mills, None

C. Griego-Fullbright, None

A. Wagner, None

E. Herding, None

V. Nordberg, None

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

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

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

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

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

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

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

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

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

G. Hansen, None

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