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New C. diff guidelines hone testing, prevention
Approaches vary widely on isolation duration
Editor's note: In this issue we conclude our two-part series on the national epidemic of Clostridium difficile (C. diff) with a look at current issues and controversies surrounding testing, discontinuing isolation and environmental cleaning.
Honing strategies against an epidemic of Clostridium difficle, the Society of Healthcare Epidemiology of America (SHEA) has issued new guideline that touch on the critical areas of diagnosis, infection control and environmental cleaning to eradicate a pathogen that is both resilient and deadly.
According to the latest data from the Centers for Diseases Control and Prevention, an epidemic of C. diff driven by the highly virulent NAP1 strain is causing some 25,000 deaths annually in hospitals and nursing homes. Developed in conjunction with the Infectious Disease Society of America, the SHEA guidelines seek in particular to sort out the confusing issues surrounding testing for C. diff. While designed primarily to guide treatment, improved diagnostics will also focus the infection control response by informing contact isolation decisions.
"It makes sense that if you have a more accurate diagnosis you will probably have better infection control also," said L. Clifford McDonald, MD, FACP, a co-author of the SHEA guidelines and an epidemiologist in the CDC's division of healthcare quality promotion.
Indeed, accurate diagnosis is crucial to the overall management of this nosocomial infection, the SHEA guidelines emphasize. Empirical therapy without diagnostic testing is inappropriate if diagnostic tests are available, because even in an epidemic environment, only some 30% of hospitalized patients who have antibiotic-associated diarrhea will have C. diff infection, the guidelines state.1
Though widely used in hospitals, the enzyme immunoassay (EIA) tests of C. diff toxin A and B which are more rapid but less sensitive than a cell cytotoxin assay are "a suboptimal alternative" approach for diagnosis, SHEA notes. The tests have been adopted by more than 90% of laboratories in the United States because of their ease of use and lower labor costs, compared with the cell cytotoxin assay. However, when compared with diagnostic criteria that included a clinical definition of diarrhea and laboratory testing that included cytotoxin and culture, the sensitivity of the EIA tests is only 63%–94%, with a specificity of 75%–100%, reports SHEA.
"The clinical community knows [the EIA] is not that sensitive. There is a psychology in the person ordering the test that, "Even if it's negative I'm going to go ahead and treat them,'" McDonald told Hospital Infection Control & Prevention. "It doesn't always link with isolation either. Someone is actually getting treated for C. diff [though] the C. diff test is negative but they're not on isolation because it's negative. Some people are being treated empirically, still others are going untreated for just a little while until they get another test and it turns out to be positive. But some of that repeat positive testing is leading to false positives. It's just bad testing, and from an infection control standpoint it leads to some delayed diagnosis that results in transmission."
Seeking a more precise gun
One potential strategy to overcome the problem is a two-step method that uses EIA detection of glutamate dehydrogenase (GDH) as initial screening and then uses the cell cytotoxicity assay or toxigenic culture as the confirmatory test for GDH-positive stool specimens only, the SHEA guidelines suggest in an "interim" recommendation. In addition, polymerase chain reaction [PCR] testing is rapid, sensitive and specific, but "more data on [PCR] utility are necessary before this methodology can be recommended for routine testing," SHEA reasoned.
"We tried to leave [the PCR option] open," McDonald said. "The two-step algorithm where people use antigen tests it is an EIA but it's not for the toxin, it's for the antigen. It's touted as being highly sensitive but not as specific, so if you had a positive antigen then you would follow it up with some other test to confirm that it was positive. There has been some back and forth in the literature about whether that could be as sensitive and specific as a PCR. We wanted to get the message across that the current modus operandi with EIA is not good enough. We need to get to something better."
Improved diagnostics and communication with the hospital lab were among the many C. diff topics discussed recently in Atlanta at the Fifth Decennial International Conference on Healthcare-Associated infections. "Dialogue with the people in the laboratory and ask if you can move toward a more [sensitive] testing methodology or paradigm," McDonald said at the meeting. "Also, at the same time restrict this testing only to unformed stool."
Focus testing on patients with more than three unformed stools within 24 hours, he advised. "The whole idea is to get a more precise gun and pull the trigger selectively," he said. Some audience members at the meeting suggested that nurses be given the green light to order testing, particularly because they have long been rumored to know C. diff by its distinctive smell.
"I wonder if one of your interventions shouldn't be automated nurse driven C. difficile toxin assay ordering," said Bryan Simmons, MD, epidemiologist at Methodist hospital in Memphis. "I see that in fact it's happening in my practice. The nurses are starting to do it. They say there was a bowel movement at 3 a.m., it smelled bad and they order the C. diff [test]. Bingo we have the diagnosis. If you wait for the [physician] to finally discover the diarrhea you will wait three or four extra days."
McDonald responded, "I do think that nursing picks up on it and it's not just 'smell.' There's a lot more going in to it. First of all [the nurse] has actually talked to the patient. Often times it is the "first" stool they've had in the facility but they've actually had three more but didn't tell anyone. A lot of that is the nurses taking a history."
Episodes of diarrhea may also trigger contact precautions for the patient, but there is considerable discussion about exactly when that isolation should end. The SHEA guidelines recommend maintaining contact isolation for the duration of diarrhea for C. diff patients. However, like anything else with C. diff, there are a variety of approaches being tried, and a lot of them depend on the situation an individual facility is facing.
"Some feel that precautions can end as soon as the diarrhea is gone some don't," said Ruth Carrico, PhD, RN, CIC, a veteran IP and assistant professor of health promotion and behavioral sciences at the University of Louisville (KY). "This is due to the shedding issues. You may continue that for 48 hours and some may elect to continue to discharge. You [may even] have conflicting written orders. How does staff understand what they are supposed to do? Are they supposed to contact someone in infection prevention? Are they supposed to disregard the physician order? Are they in a position where they are going to challenge an order? So you have to think about how you are going to apply these [recommendations] not only how you should apply them intellectually but [within] the culture of your particular environment."
The threat of asymptomatic carriers
As a supplemental infection control measure, extending use of contact precautions beyond duration of diarrhea (e.g., 48 hours) may prevent transmission from asymptomatic C. diff carriers, McDonald noted.
"We know that people remain colonized after they have recovered for some period of time probably for several weeks," he said. "So there is a subset of these asymptomatic carriers. There are others also that never had C. diff diarrhea but became colonized. [Extending isolation] addresses a subgroup of asymptomatic carriers that are more likely to develop diarrhea at some point. That's another reason to continue [isolation], because not only are they asymptomatically colonized and their environment likely contaminated, but they are also likely at any point to come back with some explosive diarrhea and really contaminate the environment in a big way."
In an informal poll at a decennial C. diff session, the audience was split across the spectrum, with roughly a third isolating for the duration of diarrhea, a third some period beyond that, and a third until hospital discharge. "Some of this is also because sometimes it is just hard practically to determine if the diarrhea is over," McDonald said. "We say in our [CDC] isolation guidelines to isolate for the duration of diarrhea, but we don't go into how to define when diarrhea has stopped."
By the same token, if you are placing all patients with diarrhea under contact precautions, remember again that only about a third of those will have C. diff, he reminded. "There is a lot of diarrhea in hospitalized patients. If you define diarrhea as simply one loose stool there is an awful lot and C. diff accounts for only 30% to 40% of that. Isolating everyone with diarrhea until you get results back might not be feasible depending on [test] turn-around time."
Even though most hospital patients with diarrhea will probably not have C. diff, Carrico recommended implementing isolation measures and sorting out the pathogens later. "We know that any time a patient can't be responsible with their body fluids then we have to figure out a way to prevent the potential transmission of whatever is causing that," she said.
Directly observe cleaning practices
A key part of blocking transmission to other patients is keeping the C. diff patient environment clean, and again there are a variety of approaches being undertaken in this regard. SHEA recommends the use of chlorine-containing cleaning agents or other sporicidal agents to address environmental contamination in areas associated with increased rates of C. diff infections. However, just as with extending duration of isolation precautions, some IPs are going well beyond this recommendation and casting a wide, wet net of bleach all over the hospital.
"There is no conclusive recommendation on these [approaches]," said Dale Gerding, MD, lead author of the SHEA guidelines and associate chief of staff for research at the Hines VA Hospital in Chicago. "As an added step if you are having a problem with C diff infections or having an outbreak then extending isolation to discharge is one way to deal with it. But that's an optional recommendation. That's not a standard recommendation. It's reserved for places that are having problems so is bleaching. Bleach can be used as an environmental cleaning product. It is an adjunct approach to infection control if you are having problems. Now many hospitals have just gone to bleach automatically and use it all the time. There housekeepers are using bleach all over the hospital, but there are not clear data as to whether it has been effective to do it that way."
The SHEA guidelines add a caveat regarding bleach, warning that "use of chlorine-containing cleaning products presents health and safety concerns, as well as compatibility challenges that need to be assessed for risk. However, current evidence supports the use of chlorine-containing cleaning agents (with at least 1,000 ppm available chlorine), particularly to address environmental contamination in areas associated with endemic or epidemic CDI." The whole issue of C. diff in the environment seems to have reached critical mass, as a wide variety of disinfection and removal products were discussed at the decennial conference.
"What is apparent is that a lot of vendors are interested in trying new methods, whether that is going to be successful and practical remains to be seen," Gerding said. "Because some of [the cleaning systems] could occupy room time for considerable periods and that's a significant factor when you are trying to turn over beds in hospitals."
That said, it is becoming increasingly clear that the environment is a significant source of C. diff, and many infection preventionists are targeting interventions accordingly. According to the SHEA guideline, C. diff spores can survive in the environment "for months or years and can be found on multiple surfaces in the healthcare setting." Furthermore, there are several reports that interventions to reduce environmental contamination by C. diff have decreased the incidence of infection.
"You can never sort out whether the patient themselves is the source of the organism or whether it is the environment," Gerding said. "The patient can have C. diff spores on their skin and pick it up that way. But the environment can be contaminated and they can pick it up just by touching the environment. It's not real clear, but there are some data that bleaching in the environment does reduce rates when they are high. Now when rates are low or not particularly high then bleaching didn't do anything. That's probably because they were just bleaching the rooms of patients with C. diff. If you have a low rate that means you aren't bleaching many rooms."
In that regard, it is important to assess the adequacy of your cleaning regimens rather than focusing solely on the product or solution, McDonald said. And it's not just missing areas, but the cleaning protocol itself that should be scrutinized, Carrico advised.
"I observed practice [at a hospital] and they were excellent at cleaning, but their process was to do the bathroom first and then come out to the rest of room," she said. "That may not be the right order you want to teach your environmental services. You may want to save the most grossly contaminated area for last, and really look at practices like returning cleaning cloths to buckets. I can't overemphasize the need to really know what's happening by observing practice. "