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AMSTERDAM, June 24 -- The use of radio frequency identification technology, already introduced in some healthcare facilities, may cause medical equipment to malfunction, researchers found.

The technology -- familiarly used in security access cards, electronic toll collection systems, and antitheft tags in retail stores -- created 34 occurrences of electromagnetic interference out of 123 tests when it was placed near a variety of critical care equipment, Erik Jan van Lieshout, M.D., of the Academic Medical Center here, and colleagues reported in the June 25 issue of the Journal of the American Medical Association.

The majority of the incidents (22) were classified as hazardous, meaning that they had a direct physical influence on the patient -- completely stopping an infusion pump, for instance.

"Implementation of [radio frequency identification] in the ICU and other similar healthcare environments should require on-site [electromagnetic interference] tests in addition to updated international standards," the researchers said.

Radio frequency identification has been proposed as a method of improving patient safety and keeping track of medical equipment and devices, the researchers said, but data on the effects of electromagnetic interference on critical care equipment are lacking.

To explore the issue, the researchers evaluated the effect of two radio frequency ID systems -- one passive (868 MHz) and one active (125 kHz) -- when they were placed near 41 different medical devices, including infusion pumps, external pacemakers, mechanical ventilators, dialysis devices, intra-aortic balloon pumps, and defibrillators.

A passive radio frequency identification tag must be activated and powered by an electromagnetic field generated by a reader in order to transmit information by radio waves. An active tag is powered by batteries and can collect, store, and broadcast information without activation by a reader.

Out of 123 tests, there were 34 incidents of electromagnetic interference -- 22 of which were hazardous, two labeled significant (they influenced monitoring to a degree that caused distraction from patient care), and 10 defined as light (they influenced monitoring, but did not require a significant level of attention).

The passive system was more likely to induce interference than the active system (in 63% of tests compared with 20%; difference 44%, 95% CI 27% to 53%, P<0.001).

Likewise, the passive system created a significantly greater proportion of hazardous incidents (41% versus 12%; difference 27%, 95% CI 12% to 41%, P=0.007).

The median distance between the radio frequency identification reader and the medical device for all types of electromagnetic interference was 30 cm (range 0 to 600) and for hazardous incidents was 25 cm (range 5 to 400).

The authors acknowledged that the study was limited by the generalization of the incidents.

In addition, they said, the results only apply to the two systems evaluated.

And finally, they noted, the systems were tested at full power to evaluate worst-case scenarios.

In an accompanying editorial, Donald Berwick, M.D., president and CEO of the Institute for Healthcare Improvement in Cambridge, Mass., wrote that the study "is of urgent significance."

Although previously there were no studies on the safety of radio frequency identification in healthcare, the technology has already been introduced into many hospitals.

Radio frequency identification tags are found in remote monitoring equipment, as tiny chips that identify items in inventory, or on surgical sponges to keep track of them during an operation, wrote Dr. Berwick.

The two systems that were evaluated in the study are not much different from other systems, he wrote, "and attention must be paid to these disturbing findings."

Rather than implementing an outright ban on the technology, which would be an overreaction, he said, hospitals should become more vigilant in monitoring potential electromagnetic interference problems, particularly in critical care units.

Also, he said, regulatory agencies should determine if new guidelines on use of the technology are warranted, and manufacturers should be more careful in testing potentially harmful interactions with equipment other than their own and should seek designs to mitigate the effects.

Above all else, Dr. Berwick said, the results of the study reinforce the lesson that new technology almost always comes with unexpected problems.

"Healthcare is full of tightly coupled, hard-to-see systems, and the naive introduction of a change as apparently isolated as [radio frequency identification] tags on endoscope tubes might cause remote and dire consequences far away in space and time," he said.

The study was funded by the Dutch Ministry of Health, Welfare, and Sport, the Ministry of Economic Affairs, the Academic Medical Center, Capgemini, Geodan, Oracle, and Intel. The authors made no financial disclosures.

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