American College of Gastroenterology Annual Meeting
American College of Gastroenterology Annual Meeting
Perspective from Gautam Mankaney, MD
October 28, 2019
2 min read

Repeat PCR testing ‘should not be used’ to predict recurrent C. difficile infection

Perspective from Gautam Mankaney, MD
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Srishti Saha
Srishti Saha

SAN ANTONIO — The median time to a first negative stool polymerase chain reaction test after the treatment of Clostridioides difficile infection was 9 days, which helped to indicate when physicians can expect to see a negative test, according to data presented at the American College of Gastroenterology Annual Meeting

“The results from our study provide a time frame within which physicians can expect stool PCR for C. difficile to become negative,” Srishti Saha, MBBS, MD, a postdoctoral research fellow at Mayo Clinic in Rochester, Minnesota, told Healio Gastroenterology and Liver Disease. “This is valuable in interpreting results of a repeat test in patients who have persistent or recurrent diarrhea post-CDI treatment.”

Saha and colleagues conducted a prospective study of 50 patients (median age, 51 years; 66% female) with CDI at the Mayo Clinic from October 2009 to May 2017.

Twenty-four percent had prior CDI.

Time to first negative PCR test from the start of treatment served as the primary endpoint.

An additional endpoint included time to first negative PCR by treatment received – metronidazole vs. vancomycin.

Half of the patients received metronidazole, while 44% received vancomycin. The remaining patients received combination of metronidazole and vancomycin (n = 2) and fidaxomicin (n = 1).

Clostridioides difficile infection is the most common health care associated infection in the United States, with several tests available for its diagnosis,” Saha said in an interview. “PCR, one of the most commonly used tests, is highly sensitive but can remain positive after appropriate treatment of CDI. Often, patients continue to have diarrhea after their CDI episode. Repeat testing with PCR in such a scenario presents a clinical conundrum, as it can represent recurrence of CDI, or persistent colonization with the bacteria.”

As a result, Saha noted that it raises many questions as to how long a PCR remains positive after CDI treatment, as well as does the type of antibiotic treatment impact the time to a negative PCR.

“We found that PCR became negative a median 9 days after treatment initiation,” she said. “This was not affected by antibiotic treatment received. Patients who had a positive PCR during treatment tended to have a higher risk of recurrence within 56 days of treatment, though this was not statistically significant. Patients with a positive PCR after treatment completion did not have higher risk of recurrence.”

Saha noted that this study is one of few looking at repeat PCR testing in CDI and its implications.

“The results are promising and indicate that PCR positivity may have a role in recurrence prediction, though this would need to be confirmed in a larger study,” she said. “Our results also suggest that at present, repeat PCR testing should not be used to predict recurrence.” – by Ryan McDonald


Saha S, et al. Abstract 5. Presented at: American College of Gastroenterology Annual Scientific Meeting; Oct. 25-30; San Antonio.

Disclosures: The researchers report no relevant financial disclosures.