In this episode, I’ll discuss whether recent laxative use should preclude testing for C diff.
The recently updated IDSA C Diff guidelines make the following recommendation:
Patients with unexplained and new-onset ≥3 unformed stools in 24 hours are the preferred target population for testing for CDI (weak recommendation, very low quality of evidence).
In the details that support this recommendation, the guideline authors make the following statement:
Clinicians can improve laboratory test relevance by only testing patients likely to have C. difficile disease. This includes not routinely performing testing on stool from a patient who has received a laxative within the previous 48 hours.
This statement is based on a single-center retrospective study of 150 patients looking at the specificity of various C diff tests in comparison with clinical symptoms.
Such a recommendation, even though it is labeled as weak and based on very low-quality evidence is likely to make its way into hospital protocol in the form of automatically discontinuing a C diff test for a patient with recent laxative use.
A group of authors sought to add to the sparse amount of data available on this topic by conducting a retrospective study of 209 patients with new-onset diarrhea and a positive C diff test.
About one-third of the patients in the study had received a laxative within the previous 48 hours. The authors found there were no significant differences in the proportion of patients meeting severe C diff infection criteria in patients receiving versus not receiving laxatives. This finding was consistent across 4 different methods used to assess disease severity.
In addition, there was no difference in the rates of serious C diff infection-related outcomes such as death, ICU admission, and colectomy in patients receiving versus not receiving laxatives.
The authors conclude that
Precluding recent laxative users from CDI testing, as proposed by the IDSA-SHEA guideline, carries a potential for harm due to delayed diagnosis and treatment.
I tend to agree that this guideline recommendation does have the potential to increase the risk of harm, especially if automatic discontinuation of C diff testing for patients with recent laxative use is implemented. A policy like this would be attractive as it is seen as having the potential to reduce the number of asymptomatic colonizers of C diff that are counted in a hospital’s quality data when tracking inpatient C diff rates. Such an automatic policy is often opaque to clinicians, and days may go by with everyone “waiting on the test results” before it is discovered the test was auto-canceled.
One reason for the lack of difference in C diff infection severity between groups may be the arbitrary cut-off of 48 hours for previous laxative use which makes little sense when compared to the pharmacodynamics of common laxatives.
Miralax: Onset of 24 to 96 hours
Dulcolax: Onset of 6 to 12 hours
Senna: Onset of 6 to 24 hours
Given that there is now as much evidence against as there is for withholding C diff testing in a patient with recent laxative use, consideration should be given to re-wording this section of the guidelines until more conclusive data is available.
Members of my Hospital Pharmacy Academy have access to practical trainings on C. diff, including the Pharmacist’s Role in Preventing C. diff Infection in the ICU and pearls on treatment and prevention strategies. To learn more, go to pharmacyjoe.com/Academy.
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