Medical devices Inspector Gadget would love

Washington -- Patients with diabetes who test their glucose levels using credit card-size devices represent just the tip of the iceberg when it comes to the potential of small and powerful medical diagnostics.

How about using sensor arrays, also called electronic noses because they are based loosely on the principles of the olfactory system, to "sniff" out lung cancer? Such arrays could move out of the lab soon.

Tiny and potent devices are already allowing physicians to monitor patients' chronic conditions without the necessity of an office visit and the more slight in size these devices get, the more muscle they seem to have.

"We are moving toward a time in the not-too-distant future when we really will be able to conduct thousands or hundred of thousands of tests in a small, inexpensive device," said David R. Walt, PhD, Robinson Professor of Chemistry at Tufts University, Medford, Mass., in an interview. These tools are already part of a trend toward bringing medical diagnostic services closer to the patient, he writes in the article "Miniature Analytical Methods for Medical Diagnostics" in the April 8 issue of Science.

And their use in the future promises a much different scenario for ordering tests and making diagnoses. While tests today are ordered one by one and are based on external criteria, such as a fever, rash or sore throat, "in the future we will be able to measure everything all of the time because it won't make any sense to measure one thing when you can measure all things for the same price," Dr. Walt said.

These forthcoming tests could shake up some long-held practices in the way medical care is delivered. For example, these relatively inexpensive and painless tests might be preformed at home or, perhaps on a weekly basis, at the pharmacy using a small sample of saliva, urine or fluid extracted from the skin, Dr. Walt said. "You could get a complete diagnostic profile before even going to the doctor. So this is a pretty disruptive approach to things."

Obstacles in the path

But regulatory issues could step in the way of technology's headlong race toward the little and mighty. Liability might become a concern if a diagnosis is missed -- perhaps overlooked among the thousands of results picked up by a single, wide-ranging test.

How physicians handle the enormous amount of health data produced by a single test will have to be considered, as will payment methods. The current model of physicians' ordering a specific test for a specific diagnosis and being reimbursed will have to change, Dr. Walt said.

"I think the most dramatic impact that we'll see in the next few years will have to do with technologies that move care closer to the patient," said Joseph C. Kvedar, MD, director of Partners Telemedicine in Boston and vice chair of dermatology at Harvard Medical School.

"One of the reasons we can even talk that way is because of devices that are more and more powerful but less and less expensive and smaller and smaller," he said.

These devices employ different technologies, Dr. Walt points out. Electrochemical glucose biosensors are already being incorporated in wristwatch-like gadgets used by people with diabetes to monitor glucose levels. The device generates electrical stimulation that causes fluid to pass through the skin for measurement.

Another glucose biosensor requires only a submicroliter blood sample that can be obtained virtually painlessly from many areas of the body.

Although they still are found primarily in labs, array analyses are "unequaled" in sorting through multiple substances or patterns simultaneously, Dr. Walt said, and the trend will be to bring them closer to patients. DNA microarrays are already commercially available that contain all the known genes in the human genome.

Self-contained microelectromechanical systems, called MEMS, already are in use. One example is the capsule colonoscopy, Dr. Kvedar said. The capsule, which can locate bleeding in the gastrointestinal tract, is swallowed by the patient and then transmits photos of its journey.

More patients will be given tools and feedback mechanisms so they can more effectively manage their own disease, Dr. Kvedar predicted. And because of the dramatic growth in the numbers of chronically ill people and the fact that there might not be enough health care professionals available to care for them, providing patients the ability to monitor their own well-being makes some sense, he noted.

Even providing a "smart" pedometer to help people with weight-control problems monitor their activity levels could be helpful. "There is good evidence that if patients have a reminder in their environment of what their activity level is supposed to be, they will boost it to match that level and be more effective at losing weight."

Stephen Oesterle, MD, senior vice president of management and technology for the medical technology company Medtronic, made the following prediction: "Within the next five to 10 years, it will be quite likely that the care of large populations of patients can be coordinated and managed through the use of implanted sensors speaking wirelessly through the Internet."