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No differences in CDI-related complications between toxin-positive and NAAT-positive-only CDI
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Toxin-positive Clostridioides difficile infection, or CDI, tended to be more severe than CDI that was detected through nucleic acid amplification tests, but researchers found no differences in CDI-related complications or mortality rates between cases that were detected using either approach, according to a recent study.
The findings have potential implications for diagnostic stewardship, researchers said.
“CDI, a toxin-mediated disease, has increased in incidence over the past 2 decades to become the most common U.S. health care-associated infection, resulting in an estimated 453,000 infections in 2011. Between 2010 and 2014, CDI-related hospitalizations increased by 15.7%,” Alice Y. Guh, MPH, medical officer in the Division of Healthcare Quality Promotion at the CDC, and colleagues wrote. “Increased CDI incidence and severity may be largely explained by the epidemic strain, ribotype 027, that emerged in the early 2000s. Another virulent strain, ribotype 078, has been identified mostly in Europe and is associated with serious infections similar to ribotype 027.”
According to researchers, during the ribotype 027 epidemic, cases of severe CDI were missed by toxin assays, leading to the development of nucleic acid amplification tests (NAATs), which are highly sensitive for C. difficile toxin gene detection. Previous studies suggest that toxin-positive CDI is more severe and has worse outcomes than NAAT-positive-only CDI, suggesting that reliance on NAAT diagnostic testing might lead to the overdiagnosis of CDI and, potentially, the overuse of antibiotics. To fill knowledge gaps, researchers compared toxin-positive and NAAT-positive-only CDI in terms of CDI-related complications, recurrence and 30-day mortality between the groups.
Cases used for the study were detected from 2014 to 2015 through a testing algorithm and toxin enzyme immunoassays. Tests with mixed results were reflexed to NAAT and classified as toxin positive or NAAT positive only, according to the researchers.
Overall, 4,878 cases were identified, with 2,160 being toxin positive and 2,718 being NAAT positive only. Of these cases, more toxin-positive than NAAT-positive-only cases were found in patients aged 65 years and older, had instances of three or more unformed stools for longer than 1 day and had white blood cell counts greater than 15,000/µL. Additionally, after analysis, researchers determined that toxin positivity was associated with more virulent C. difficile strains and chances for recurrence but not with CDI-related complications or 30-day mortality.
“Although toxin [enzyme immunoassay] appears to capture more severe disease that is more likely to recur, at least as presently diagnosed, there were no differences in adjusted rates of CDI-related complications and mortality between toxin-positive and NAAT-positive-only CDI. In addition, the low rate of documented clinically significant diarrhea in this analysis suggests that inappropriate testing may be common, highlighting the need for better diagnostic stewardship practices,” the authors concluded. “CDI treatment is not without harm and can result in microbiome disruption; regardless of which test is used, the decision to test and treat should take into consideration the patient’s clinical presentation and risk factors. Further advances in CDI diagnostic assays are needed to help determine which patients are likely to experience net benefit from CDI treatment.” – by Caitlyn Stulpin
Disclosures: The authors report no relevant financial disclosures.
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