Advances in IBD
Advances in IBD
December 19, 2019
2 min read

All C. difficile tests not created equal, especially among patients with IBD

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Jessica Allegretti

ORLANDO — Identifying Clostridioides difficile infection among patients with inflammatory bowel disease can be a particularly tricky task, according to Jessica Allegretti, MD, MPH, of the Brigham and Women’s Hospital Crohn’s and Colitis Center. Since both are diarrhea-predominant, there is a lot of symptoms overlap.

“Distinguishing between C. diff and IBD is very challenging,” Allegretti told Healio Gastroenterology and Liver Disease in an interview. “So how do you do that appropriately?

“I cannot stress this enough. Not all C. difficile tests are created equal, especially when you’re dealing with a patient population where the symptoms are not telling you the whole story. You have to know what test you’re using, what that test is telling you and how to act on it appropriately.”

Allegretti said many medical centers across the country are still using polymerase chain reaction (PCR)-only testing, which does not have the ability to distinguish between active colonization and infection. She urged physicians working in those institutions to understand that distinction.

“If you’re asking yourself, ‘Why is this patient not responding to vancomycin? Why are they not responding to medical therapy?’ It’s probably because they don’t have C. difficile,” she said. “They’re colonized and their IBD is really what’s driving most of their symptoms, and you need to treat the IBD appropriately.”

Often, Allegretti said, patients with consistent positive PCR results are lumped into C. difficile and not enough attention is given to the IBD.

“They’re only treated for that, and they’re continually getting worse because their IBD is being ignored,” she said. “There is inherent fear of immunosuppression in the setting of potential C. difficile.”

Rather than ignore the IBD, Allegretti said any concerned physicians who only have PCR testing at their disposal to get their patient on C. difficile therapy, and after 48 hours to escalate therapy for IBD.

“It’s appropriate to treat their IBD aggressively because the C. difficile inherently revs up the IBD as well. So, you have to treat both,” she said. “If you see that the antibiotics on board are acting, then you can feel totally comfortable that you’ve gotten that aspect at least under control. Now you need to match the aggressiveness of your C. difficile therapy with your IBD therapy.”


Allegretti J. C. diff and IBD. Presented at: Advances in Inflammatory Bowel Disease; Dec. 12-14, 2019; Orlando.

Disclosure: Allegretti reports consulting for and receiving research support from Finch Therapeutics and Merck. She also reports being an unpaid scientific adviser for OpenBiome.