Clostridium difficile infection is one of the most common healthcare-associated infections in adults in the United States. Older Americans are especially vulnerable to CDI,2 and this infection has been increasingly recognized as a significant burden in community and nursing home settings.

A major challenge in C. difficile testing is that no single test currently available has high enough sensitivity and specificity to identify true CDI. Molecular methods offer sensitivity without specificity, while toxin options are specific but lack sensitivity. As a result, the Infectious Diseases Society of America and the European Society of Clinical Microbiology and Infectious Diseases recommend using complex, multistep testing algorithms for CDI diagnosis.

Data from three studies reported at the European Congress of Clinical Microbiology and Infectious Diseases in April and the American Society of Microbiology this month indicate that a single-test solution which meets current guidelines for identifying CDI may soon be available from Singulex, Inc. The Singulex Clarity C. diff toxins A/B assay was shown to be as sensitive as PCR-based methods and more specific than traditional immunoassays.

One study conducted with Niaz Banaei, M.D., at Stanford University Medical Center, demonstrated the Singulex Clarity C. diff toxins A/B assay yielded 98% sensitivity and 100% specificity compared to multistep PCR-and-toxin testing.  It was concluded that the assay is ultrasensitive and highly specific and may offer a standalone solution for the rapid detection and quantitation of free toxins in stool.

A second study evaluated the analytical performance of the Singulex Clarity C. diff toxins A/B assay and showed that the assay can detect C. difficile toxins at concentrations lower than commercially available toxin assays and that it had high sensitivity and specificity compared to CCNA. The Singulex Clarity C. diff toxins A/B assay demonstrated reactivity to common C. difficile strains, did not show cross-reactivity to common gastrointestinal pathogens, was robust against common interferents at relevant concentrations, allowed for detection of toxins in both fresh and frozen stool samples and up to three freeze-thaw cycles, and provided results with high reproducibility.

In an additional study, the clinical performance of the Singulex Clarity C. diff toxins A/B assay compared to CCNA and relative to current C. difficile testing options was determined in a study together with TriCore Reference Laboratories in Albuquerque, New Mexico, USA. When assessing sensitivity and specificity compared to CCNA, the Singulex Clarity C. diff toxins A/B assay outperformed PCR, EIA, and two multistep algorithms.

CDI presents challenges to hospital infectious disease specialists, clinicians, nurses, administrators, laboratorians, as well as to patients and families. A single test that offers high sensitivity, high specificity, and faster turnaround times could greatly improve CDI diagnosis and patient management. Singulex anticipates FDA registration for the Singulex Clarity C. diff toxin A/B assay by the end of 2018.

Niamh Nolan is Director of Clinical Research and Medical Affairs at Singulex