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With diversion, lower blood culture contamination rates

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Anne Ford

July 2017—To stage magicians, diversion is a trick—a way to direct the audience’s attention to something irrelevant so they don’t notice what they shouldn’t see.

To those who perform blood cultures, diversion is also a trick, though there’s nothing deceptive about it—and the way it helps avoid contamination can seem like magic.

“The diversion method, simply stated, is a way to re-route potentially contaminated blood into a separate tube or pouch before filling the sterile blood culture bottles. It is a way to ‘flush the line,’ ” says Janis Atkinson, MD, laboratory medical director at Presence Saint Francis Hospital in Evanston, Ill. “Studies done in platelet procurement using the diversion method have shown that contamination rates can be reduced by as much as 50 percent, with an 85 percent reduction of contamination by skin flora. For that reason, diversion is standard operating procedure in blood bank protocols.”

Dr. Atkinson

Dr. Atkinson

Dr. Atkinson and colleagues recently implemented a protocol they designed in their lab that uses diversion to reduce blood culture contamination. “The protocol uses no special equipment,” Dr. Atkinson says, “and the design is simple: Change the order of the blood draw tubes so the culture bottles are not ‘up first in line.’ ”

Now, a new product from Magnolia Medical Technologies, the SteriPath initial specimen diversion device, makes it possible to reduce contamination of blood cultures by diverting, sequestering, and discarding the first 1.5 to 2 mL of blood.

Invented by Magnolia Medical Technologies founder and medical director Richard G. Patton, MD, the SteriPath device was the subject of a study published in April and conducted by Mark E. Rupp, MD, and others (Rupp ME, et al. Clin Infect Dis. April 3, 2017 Epub ahead of print. doi:1093/cid/cix304). Dr. Rupp is a professor and chief of the University of Nebraska Medical Center Division of Infectious Diseases and medical director of the Department of Infection Control and Epidemiology at Nebraska Medicine, Omaha.

Dr. Patton, former chief of pathology and medical director of clinical laboratories at Northwest Hospital, Seattle, gives a quick description of the device: “A venipuncture wheel allows flow of blood into the reservoir where the sequestered fragments of skin are captured, and once that reservoir is filled, there’s a trigger device that shunts the flow of blood into another channel where the blood culture bottle is present.”

In the study, which examined 1,808 blood cultures, trained phlebotomists drew two samples from each patient—one using a standard syringe and the other the SteriPath device. If coagulase-negative staphylococci, Propionibacterium sp., Micrococcus sp., viridans group streptococci, Corynebacterium sp., or Bacillus sp. were recovered from one of the paired cultures, the culture was considered contaminated. Slightly more than one percent of the blood cultures proved to be contaminated. The standard draw yielded a contamination rate of 1.78 percent, while the SteriPath device yielded a contamination rate of 0.22 percent. (The American Society for Microbiology sets the target rate for acceptable blood culture contamination at three percent.)

“When you’re talking about less than two percent contamination, most folks feel like that’s a pretty low number, and it doesn’t seem to be very significant,” Dr. Rupp says. “But when you understand that about 30 million blood cultures are done throughout the United States every year, two percent would be about 600,000 contamination events. There are a number of studies that show the amount of money that’s associated with a contamination event is thousands of dollars.”

Dr. Rupp

Dr. Rupp

One limitation to the study, he cautions, is that the researchers were required to obtain informed patient consent. “So, for instance, it excluded all the patients who had to have emergent procedures. It excludes everybody who was obtunded or couldn’t grant consent. Because you’re under a lot of time pressure in the emergency department, pretty much everybody who didn’t speak English was excluded because of the time it would take to get a translator and do the informed consent procedure,” he says. “So the phlebotomists had to bypass a lot of patients, and we had potentially a biased patient population.” In addition, the phlebotomists indicated they purposely avoided using the SteriPath device on combative patients or patients with small, fragile, or otherwise difficult-to-access veins.

One limitation of the device itself is that “you may not want to use it in somebody with a very low blood volume,” Dr. Rupp says. For instance, “in our neonatal ICU where they have very low blood volumes, every milliliter is precious, and so you wouldn’t want to draw off a couple of milliliters that you discard.”

There is also the environmental effect to consider, given that the SteriPath is a single-use device. “The packaging we have is as minimal as possible,” Dr. Patton says, “and we have the device set up so that it can be disposed of in a safe fashion, and I think that’s all we can do, environment-wise and safety-wise.” He adds that since blood culture contamination has been shown to result in unnecessary laboratory tests, imaging studies, and antibiotic use, as well as increased length of stay, “given the fact that contamination is near zero with SteriPath, there may be a big environmental improvement.”

Then, too, “In a paradigm shift, SteriPath is expected to obviate the need for a second venipuncture in the blood culture process.

“The advantage of diversion in the first venipuncture enables an even lower contamination rate in the second culture without a second venipuncture,” Dr. Patton says, pointing out that environmental improvement accrues as the second venipuncture, “with it’s paraphernalia and inconven­ience, becomes redundant.”

The Medical University of South Carolina’s emergency department began using SteriPath last year in an attempt to lower its contamination rate, which, despite many efforts, had for several years never dropped below four percent. Director of diagnostic microbiology Lisa Steed, PhD, calls the pre-2016 rate “unacceptably high.”

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