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

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.

rRNA Analysis Based on Long-Read High-Throughput Sequencing Reveals a More Accurate Diagnostic for the Bacterial Infection of Ascites

“…C. difficile produces metabolically inactive endospores, making it is resistant to gastric acid and most kinds of antibiotics [21]. C. difficile can produce two toxins: enterotoxin A and cytotoxin B [22]. The pathogenicity of C. difficile is based on the fact that at least one of the two toxins acts as a glycosyltransferase to modify guanosine triphosphatases in intestinal epithelial cells and cause the disruption of the actin cytoskeleton [23].…”

The future of Clostridioides difficile diagnostics

“…Using the same toxin cutoff as in the Hansen article, the study demonstrated high agreement with the testing algorithm [55 ▪ ]. The authors concluded that the Singulex Clarity assay is a stand-alone testing solution for the diagnosis of C. difficile [55 ▪ ]. Unfortunately, the company decided not to pursue commercial application of the Clarity assay.…”

“…In a multicenter study evaluating the Clarity automated assay using the manufacturers’ toxin cutoff of 12 pg/ml of stool, Hansen et al [54] demonstrated a positive percent agreement after discrepant analysis of 96.3% and a negative percent agreement of 93.3% compared with CCNA as the reference method. In a recent single center study by Landry et al [55 ▪ ] the authors compared the Clarity assay with a standard of care testing algorithm using GDH and toxin EIA arbitrated by CCNA. Using the same toxin cutoff as in the Hansen article, the study demonstrated high agreement with the testing algorithm [55 ▪ ].…”

“…In a recent single center study by Landry et al [55 ▪ ] the authors compared the Clarity assay with a standard of care testing algorithm using GDH and toxin EIA arbitrated by CCNA. Using the same toxin cutoff as in the Hansen article, the study demonstrated high agreement with the testing algorithm [55 ▪ ]. The authors concluded that the Singulex Clarity assay is a stand-alone testing solution for the diagnosis of C. difficile [55 ▪ ].…”

Clostridioides difficile Diarrhea: An Emerging Problem in a South Indian Tertiary Care Hospital

“…Recently, an automated ultrasensitive toxin assay was approved by US Food and Drug Administration, which showed comparable sensitivity with the testing algorithm utilizing a GDH-and-toxin EIA and cell cytotoxicity neutralization assay. 11 A study was conducted for comparing the C. difficile toxin concentration in adults with symptomatic infection and asymptomatic carriage using the ultrasensitive quantitative immunoassay, which failed to yield any difference. 12 The GeneXpert, however, in our study did not detect any hypervirulent ribotype 027 strain.…”