Dr. Halamka, who is chief information officer at Beth Israel Deaconess Medical Center (BIDMC) and Harvard Medical School, as well as an emergency room physician, has a radio frequency identification (RFID) chip implanted in his own arm that would allow anyone with a handheld RFID reader to scan his arm and obtain his 16-digit medical identifier.

The chip, which consists of several small components encased in an unbreakable glass capsule, was implanted in his arm in December 2004 with only a local anesthetic. Any authorized health care worker can visit a secure website hosted by the chip manufacturer and retrieve information about his identity and that of his primary care physician, who could provide medical-history details.

Hackers May Pose Threat

"For patients with Alzheimer’s disease who wander away from home, an identifier that enables caregivers to identify non-verbal or confused patients and determine their health care preferences could be very desirable," Dr. Halamka says.

But a number of significant legal, ethical and technological hurdles need to be overcome first.

"Since my chip contains only my medical identifier, unauthorized reading would not disclose health information," notes Dr. Halamka. "But nothing is simple," he adds. Technology similar to the "spyware" that infests computers after users visit certain Internet sites might be used to track him, he points out, in the absence of specific privacy measures.

There are also significant ethical questions about inserting chips in patients incapable of proving informed consent. Computer hackers continue to be one step ahead of developers and have shown the ability to break the encryption of existing chips used to purchase gasoline and provide automobile security, for example.

And the technology is not cheap: Each medical ID chip costs $200 and a reader costs $650, raising the question of whether it is a practical investment.

Marked Man?

Dr. Halamka reports his chip has resulted in no discomfort -- even as he has maintained an active lifestyle encountering extremes of temperature, wind and water while rock and ice climbing.

If he should wish to upgrade the chip, it would require minor surgery. Otherwise, it is expected to last at least 10 years, can safely undergo magnetic resonance imaging, and passes through airport security systems without incident.

But one of the greatest potential hurdles to widespread adoption may be psychological.

"It is clear there are philosophical consequences to having a lifelong implanted identifier," Dr. Halamka admits. "Friends and associates have commented that I am now 'marked' and lost my anonymity. Several colleagues find the notice of a device implanted under the skin to be dehumanizing. I have not investigated these or other moral, religious or political implications," he says.

"On the basis or my unscientific study with a sample of one, I conclude that there may be appropriate uses, that there are privacy concerns that must be accepted by the implantee, and that we need to establish standards that permit seamless, secure access to information," Dr. Halamka concludes.