With the support of the Program of Hospital Epidemiology, as of Friday, December 11th, 2020 the order of testing in the “C. difficile toxin screen” (Epic LAB8239) will be reversed, with C. difficile PCR preceding reflex testing with C. difficile toxin antigen testing. This will increase turnaround time in the laboratory to two hours or less in total, and will simplify resulting and interpretation as follows:

1. Negative for toxin genes by PCR: C. difficile not detected, no further testing to follow.
2. Positive for toxin genes by PCR AND negative for C. difficile toxin antigen: C. difficile colonization is most likely but infection is possible.
3. Positive for toxin genes by PCR and positive for C. difficile toxin antigen: consistent with active C. difficile infection.

The order itself, sample type (raw stool), sample rejection criteria, and interpretive comments will remain the same.

Because sensitivity for both colonization and infection will remain high under this new algorithm, the Program of Hospital Epidemiology (PHE) continues to recommend the following measures to identify patients with the highest likelihood of having C. difficile infection (CDI).

• Only send a C. diff test on patient with new unexplained onset diarrhea.
• Rule out recent laxative administration in the past 48 hours.
• Only unformed or watery stool samples sent for testing will be analyzed, except in rare cases of ileus; prior authorization from the lab is needed in these cases.
• Do not send multiple samples for testing to diagnose CDI (in the past 14 days for a previous positive test or within 7 days of a negative test).
• Do not test for cure.
• Isolation precautions may be discontinued 48 hours following last diarrhea symptom without a need to retest.

Questions concerning this broadcast can be directed to Bradley Ford, MD, PhD, Medical Director of Microbiology; (ext. 6-2990, bradley-ford@uiowa.edu), or or Dan Diekema, MD, MS, Associate Hospital Epidemiologist ; (ext. 4-5626, daniel-diekema@uiowa.edu).