The Factors that Matter in C. Difficile Screening
MAY 02, 2018
MD Magazine Staff
Peter Salgo, MD: I want to discuss some of the diagnostic methods that we’ve got for making this diagnosis. Somebody with diarrhea, outside of the hospital, inside the hospital, it’s a different kettle of fish, I suspect? What are the potential causes of diarrhea?
Darrell S. Pardi, MD: There are a dozen potential causes of diarrhea that we have to think through. As Dale said, Clostridium difficile [C. diff] is the most common nosocomial infection. But a minority of patients with diarrhea, even in the hospital, are still C. diff-positive. The diarrhea is due to C. diff. There are also many other things: medications, being very common, and other infections, tube feeding, other gastrointestinal disorders, other causes of colitis, etc., malabsorption. It’s a long list.
Peter Salgo, MD: Diarrhea is not C. diff until proven otherwise?
Darrell S. Pardi, MD: Correct.
Peter Salgo, MD: Diarrhea is a spectrum, if I hear you correctly?
Darrell S. Pardi, MD: Yes.
Peter Salgo, MD: Now, that’s in the hospital. What about in the outpatient setting? Is it the same? Is it more common? Less common? What do you think?
Darrell S. Pardi, MD: It’s probably less common, if you control for things like age and comorbidities. An older person with comorbidities and antibiotic exposure would be at risk in the hospital or in the community. The interesting thing is, when you look at community-acquired C. diff, many of those patients have not had a recent hospitalization or antibiotic exposure. So, it’s present in the community. It has to be thought of, but it’s less common than in a hospitalized patient.
Peter Salgo, MD: I have pity for the poor primary care physician. Here’s somebody, coming to that person, who says, “I’ve never had” or “I haven’t had antibiotics in years. I’ve never had a diarrheal illness. No one in my family has had a diarrheal illness. Nobody that I know of, who is in the hospital, has diarrhea. Yet, you’re telling me it could still be C. diff? Why?”
Darrell S. Pardi, MD: We don’t know.
Peter Salgo, MD: Well, there’s a refreshing answer. We don’t know.
Darrell S. Pardi, MD: We did a study on community-acquired C. diff at the Mayo Clinic. We found that 40% of the C. diff in our county was community acquired. But if you think about our county, a large proportion of patients work in the hospital or in the doctor’s office. So, you don’t have to be a patient. You just need exposure to a healthcare environment.
Peter Salgo, MD: What about pediatricians versus adult doctors or primary care physicians who have a practice which covers this waterfront? Are kids with diarrhea different from adults with diarrhea?
Dale N. Gerding, MD: Absolutely.
Peter Salgo, MD: How so?
Dale N. Gerding, MD: Kids, for one thing, often are colonized with C. diff in the stool asymptomatically. For infants, in particular, the pediatric recommendation is now to not test up to the age of 1 year. And if you’re dealing with toddlers in the 1- to 2-year age group, look for other things first. Do not test them frequently.
Peter Salgo, MD: I’ve got little kids. If you were to test for it every time any one of my little kids had diarrhea, I think we’d be at the doctor’s office every day with one or the other. So, when you’re screening patients for C. diff, what are the factors that you have to rule in, or rule out, before you start?
Darrell S. Pardi, MD: This goes back to Yoav’s earlier comment about appropriate testing, and this gets back to the notion of pre-test probability. If someone is on laxatives or another medication that is known to cause diarrhea, such as lactulose, for example, which is commonly used in the hospital….
Peter Salgo, MD: It’s almost guaranteed to cause diarrhea, as a direct effect.
Darrell S. Pardi, MD: That’s how they work. So you should probably stop that medication and see how they do before you test for C. diff. This gets into the notion of C. diff carriage. We don’t have good tests to distinguish between carriage and true infection. So we have to do the testing in the appropriate patient.
Peter Salgo, MD: You said 3 out of 4 stools in 24 hours?
Yoav Golan, MD: Well, yes. Three will be the minimum definition. Most people with C. diff will actually have a higher frequency. But when it comes to determining who to test, the most important thing is that when you test, you try to answer a question. That question should be, does the patient have unexplained diarrhea? If you can explain the diarrhea by taking medications, by getting tube feeds, or just by getting an oral contrast for a CAT scan, which is so common in hospitals, that will open up anyone, even the most constipated person…. So, it has to be unexplained diarrhea. Or there needs to be a feature of the diarrhea that makes you specifically suspect it.
Peter Salgo, MD: You’re not recommending contrast media as a treatment for constipation? Just to put that on the table.
Yoav Golan, MD: No. Maybe we should study that.
Transcript edited for clarity.