Ultra-sensitive assay for Clostridium difficile toxin AB in development

A new ultra-sensitive assay for Clostridium difficile toxin A/B for use on the Sgx Clarity system, a fully automated, in vitro diagnostic platform powered by Single Molecule Counting technology (Singulex), demonstrated excellent sensitivity and a turn-around time of 1 hour or less, according to results from pilot studies presented recently at the American Society for Microbiology (ASM) Microbe 2017 conference.

In these initial pilot studies, researchers found that the Sgx Clarity C. difficile assay could detect toxin A/B levels at concentrations that were up to 100 times lower than other commercially available immunoassays. Thus, the sensitivity of the Single Molecule Counting-based C. difficile toxin A and B assay rivals that of molecular methods. In addition, turn-around time was less than 1 hour.

“Having an ultra-sensitive C difficile toxin immunoassay would be a game changer,” said Christopher Polage, MD, associate professor of pathology and infectious diseases, University of California, Davis School of Medicine.

Currently, C. difficile infection (CDI) is the leading cause of gastroenteritis-associated death, and the most common cause of health care-association infections in US hospitals, almost 500,000 infections, according to the Centers for Disease Control and Prevention. In 2011, CDI was also associated with roughly 29,000 deaths.

“Our experience shows the importance of toxin testing to identify patients with infection and minimize over-diagnosis but there’s still a lot of anxiety in the field. Labs worry about missing individual CDI cases but hospitals are facing huge financial pressures to reduce CDI and blaming labs for using tests that don’t distinguish between infected and colonized patients. Having an ultra-sensitive toxin test would allow labs to give physicians a toxin result to help maximize the accuracy of CDI diagnosis without the worry of missing cases. This would improve patient care and allow hospitals to reduce CDI rates and avoid financial penalties, representing a ‘win-win’ for everyone,” added Dr. Polage.

In clinical studies in over 130,000 subjects, results with the Singulex proprietary Single Molecule Counting technology have been validated, and the company plans on submitting these data this year for regulatory clearance of the system in the US in 2018.