1092. Tuning Down Clostridioides difficile PCR Sensitivity Reduces Treatment for C. difficile Infection in Toxin-Negative Patients with No Increase in Adverse Outcomes
Session: Poster Abstract Session: Diarrhea Diagnostic Dilemmas
Friday, October 5, 2018
Room: S Poster Hall
  • IDWeek2018_HitchcockPoster_final.pdf (345.1 kB)
  • Background:

    Studies have shown that toxin detection identifies those who require treatment for C. difficile infection (CDI) and free toxin can be predicted with high negative predictive value from PCR cycle threshold (CT). CT-toxin was introduced at our institution in two phases: from Oct. 2016 to Oct. 2017, CT-toxin was reported with the PCR result (split reporting) and CDI therapy was discouraged if CT-toxin was negative (PCR+/CTtox-). Interim analysis showed that CDI treatment had no effect on outcomes in these CTtox- patients, so starting Nov. 2017, only CT-toxin was reported. Outcomes in PCR+/CTtox- patients treated during split reporting and untreated during the toxin-only period are detailed here.


    Patients tested from Oct. 2016 to Feb. 2018 with a positive Xpert tcdB PCR (Cepheid, Sunnyvale, CA) and CTtox- result were included. Clinical data were collected by retrospective chart review in the split reporting period and prospective review in the toxin-only period and analyzed using SPSS at α=0.01.


    Of 186 unique PCR+/CTtox- patients during split reporting, 99 (53%) were treated, compared to 6 (12%, n=51) in the toxin-only period (p<0.001). In comparing treated patients during split reporting to untreated patients during toxin-only reporting (n=45), there were no significant differences in age, sex, prior antibiotic use, CDI in the previous 6 months, Charlson Comorbidity Index, patient location, immune status, or data at testing, including WBC count, creatinine, albumin, and stools/day. There were no cases of fulminant CDI in either group and no difference in outcomes (Table).


    Reporting of CT-toxin alone significantly reduced treatment for CDI compared to split reporting in CTtox- patients with no increase in adverse outcomes in short-term follow-up. Further study is needed to confirm these findings in a larger cohort.

    Table. Outcomes in patients with PCR+/CTtox- result by treatment status and reporting period. Categorical variables are denoted as n (%) and continuous variables as mean [standard deviation].


    Split Reporting

    Treated (n=99)

    CT-Toxin Only Reporting

    Untreated (n=45)


    Days to Diarrhea Resolution

    (<3 stools/day)

    2.8 [1.9]

    2.2 [2.1]


    CTtox+ CDI within 8 Weeks

    8 (8.1)

    4 (8.9)


    30-day All-Cause Mortality

    9 (9.1)

    3 (6.7)


    Matthew Hitchcock, MD, MPH1, Marisa Holubar, MD, MS1, Lucy Tompkins, MD, PhD1 and Niaz Banaei, MD1,2,3, (1)Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University School of Medicine, Stanford, CA, (2)Department of Pathology, Stanford University School of Medicine, Stanford, CA, (3)Clinical Microbiology Laboratory, Stanford University Medical Center, Palo Alto, CA


    M. Hitchcock, None

    M. Holubar, None

    L. Tompkins, None

    N. Banaei, None

    Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 3rd with the exception of research findings presented at the IDWeek press conferences.