High Agreement Between an Ultrasensitive Clostridioides difficile Toxin Assay and a C. difficile Laboratory Algorithm Utilizing GDH-and-Toxin Enzyme Immunoassays and Cytotoxin Testing

Marie L Landry; Jeffrey E Topal; Joel Estis; Phoebe Katzenbach; Niamh Nolan; Johanna Sandlund

doi:10.1128/JCM.01629-19

High Agreement Between an Ultrasensitive Clostridioides difficile Toxin Assay and a C. difficile Laboratory Algorithm Utilizing GDH-and-Toxin Enzyme Immunoassays and Cytotoxin Testing

J Clin Microbiol. 2020 Jan 28;58(2):e01629-19. doi: 10.1128/JCM.01629-19. Print 2020 Jan 28.

Authors

Marie L Landry^{1

2

3}, Jeffrey E Topal^{3

4}, Joel Estis⁵, Phoebe Katzenbach⁵, Niamh Nolan⁵, Johanna Sandlund⁵

Affiliations

¹ Department of Laboratory Medicine, Yale University School of Medicine, New Haven, Connecticut, USA marie.landry@yale.edu.
² Clinical Virology Laboratory, Yale New Haven Hospital, New Haven, Connecticut, USA.
³ Section of Infectious Diseases, Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut, USA.
⁴ Department of Pharmacy Services, Yale New Haven Hospital, New Haven, Connecticut, USA.
⁵ Singulex, Inc., Alameda, California, USA.

Abstract

The Singulex Clarity C. diff toxins A/B (Clarity) assay is an automated, ultrasensitive immunoassay for the detection of Clostridioides difficile toxins in stool. In this study, the performance of the Clarity assay was compared to that of a multistep algorithm using an enzyme immunoassay (EIA) for detection of glutamate dehydrogenase (GDH) and toxins A and B arbitrated by a semiquantitative cell cytotoxicity neutralization assay (CCNA). The performance of the assay was evaluated using 211 residual deidentified stool samples tested with a GDH-and-toxin EIA (C. Diff Quik Chek Complete; Techlab), with GDH-and-toxin discordant samples tested with CCNA. The stool samples were stored at -80°C before being tested with the Clarity assay. For samples discordant between Clarity and the standard-of-care algorithm, the samples were tested with PCR (Xpert C. difficile; Cepheid), and chart review was performed. The testing algorithm resulted in 34 GDH⁺/toxin⁺, 53 GDH^-/toxin^-, and 124 GDH⁺/toxin^- samples, of which 39 were CCNA⁺ and 85 were CCNA^- Clarity had 96.2% negative agreement with GDH^-/toxin^- samples, 100% positive agreement with GDH⁺/toxin⁺ samples, and 95.3% agreement with GDH⁺/toxin^-/CCNA^- samples. The Clarity result was invalid for one sample. Clarity agreed with 61.5% of GDH⁺/toxin^-/CCNA⁺ samples, 90.0% of GDH⁺/toxin^-/CCNA⁺ (high-positive) samples, and 31.6% of GDH⁺/toxin^-/CCNA⁺ (low-positive) samples. The Singulex Clarity C. diff toxins A/B assay demonstrated high agreement with a testing algorithm utilizing a GDH-and-toxin EIA and CCNA. This novel automated assay may offer an accurate, stand-alone solution for C. difficile infection (CDI) diagnostics, and further prospective clinical studies are merited.

Keywords: C. difficile; C. difficile EIA; C. difficile PCR; CDI; cytotoxin; single-molecule counting; toxin; ultrasensitive.

Publication types

Comparative Study

MeSH terms

Adult
Algorithms
Automation, Laboratory
Bacterial Proteins / analysis*
Bacterial Toxins / analysis*
Clostridioides difficile / chemistry*
Clostridioides difficile / enzymology*
Clostridium Infections / diagnosis
Enterotoxins / analysis*
Feces / chemistry
Female
Glutamate Dehydrogenase / analysis*
Humans
Immunoenzyme Techniques / standards*
Male
Sensitivity and Specificity

Substances

Bacterial Proteins
Bacterial Toxins
Enterotoxins
tcdA protein, Clostridium difficile
toxB protein, Clostridium difficile
Glutamate Dehydrogenase

Grants and funding

UL1 TR001863/TR/NCATS NIH HHS/United States