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Originally published January, 1998

IVD Technology News

Will next-generation glucose monitors achieve potential?

Biosensors that promise to measure blood glucose easily—and painlessly—are the holy grail of insulin-dependent diabetics. Diabetics might gain relief from the finger stabs necessary to draw blood for glucose tests and, in so doing, achieve longer and better-quality lives.

The successful developer of such a monitor stands to reap a financial windfall. The worldwide market for glucose-monitoring products exceeds $2 billion and is growing annually by double digits. More than half of this total comes from sales in the United States—and about 90% is from the disposable glucose reagent strips used in finger-stab monitoring. Painless monitors would grab an enormous chunk of this market.

There are several front-runners in this race. Cygnus, Inc. (Redwood City, CA), is developing a wrist-worn monitor called the GlucoWatch, which would use electro-osmosis to draw glucose molecules from the skin into a dermal patch for measurement. SpectRx (Norcross, GA) and Integ (St. Paul, MN) are fabricating devices that would sample interstitial fluids. The SpectRx device would use off-the-shelf glucose strip chemistry to test the fluid; Integ's LifeGuide would rely on an infrared photometer to measure glucose in the sample. Another company, Biocontrol Technologies (Pittsburgh), is developing an infrared-based device, the Diasensor 1000.

The engineering efforts by these companies have attracted the attention of several big guns in the IVD industry. Becton Dickinson (BD; Franklin Lakes, NJ) and Yamanouchi Pharmaceutical (Tokyo) are partnering with Cygnus to market the GlucoWatch—Yamanouchi in Japan and Korea, BD in the rest of the world. Meanwhile, Abbott Laboratories (Abbott Park, IL) has purchased exclusive worldwide rights to the SpectRx technology except in Singapore and the Netherlands, where the company has coexclusive rights.

The problem is that many companies are having a tough time getting their technologies to work. Biocontrol has had more than its share of problems. The company's tabletop spectrophotometer is designed to recognize a person's glucose patterns through the use of a light beam that passes through the skin of the forearm into the blood and is then reflected back to a sensor. A microprocessor is intended to interpret the data and calculate the blood glucose level.

Less than two years ago hopes were high that the company would soon get the device approved by FDA, but in February 1996 an advisory panel recommended against approval. At the meeting, the company produced successful data on only 8 patients out of the 85 enrolled in its clinical trials. The big problem was calibration. One possible reason may be that optical "signatures" of glucose levels may be as specific to patients as their fingerprints.

But according to Biocontrol spokesperson Susan Taylor, calibration was not a serious problem in a home clinical study completed late last year. "We had significantly better results from the calibration process done in the home study than in the laboratory setting," Taylor says.

The advance of such noninvasive monitors may benefit from a "sense of Congress" statement written into the FDA Modernization Act of 1997, which was signed into law in November by President Clinton. The act states that the "availability of a safe, effective, noninvasive blood glucose meter would greatly enhance the health and well-being of all people with diabetes across America and the world."

A. Paul Harding, vice president for sales and marketing at Integ, believes the statement is the result of lobbying. "That wording probably got put in at the behest of companies that are developing true noninvasive systems, a field where they're having tremendous difficulty achieving any sort of reasonable accuracy or precision."

Neither the SpectRx nor the Integ device is truly noninvasive—but both do promise to be painless. SpectRx fires a laser into the outer layer of the skin, creating micropores about 80 µm across and 20 µm deep. Integ uses a needle to penetrate the same part of the skin; there is no pain because this outer layer has very few nerve endings or capillaries.

With the SpectRx device, interstitial fluid flows into the micropore, is sampled, and is then passed to Abbott's MediSense test-strip technology, which is currently available for conventional finger-stab blood glucose testing. Integ's LifeGuide system uses light radiation rather than test strips to analyze the fluid.

Integ was hoping to be in FDA review by now but ran into problems about mid-1997. "Over the past four months we've been focusing on identifying sources of error in the system," says Harding. When the company will submit a product approval application to FDA, however, is not known. "We're basically building up a new set of instruments, and until we test them and know their performance it's impossible to predict when we'll go to FDA."

SpectRx hopes to makes its submission to FDA sometime in 1999. "We anticipate this will be a 510(k) submission, where we will just have to show substantial equivalence to predicate devices," says company spokesperson Bill Wells. "We've published data that show a very high correlation between our device and the finger-stick test."

At this point, Cygnus appears to be best positioned to commercialize its technology. The company advocates a noninvasive approach that uses low-level electrical energy to pull interstitial fluid out of the skin to a small disposable pad located between the GlucoWatch hardware and skin. The presence of glucose molecules in the fluid triggers an electrochemical reaction with a reagent in the pad, generating an electric current that is measured by an application-specific integrated circuit.

The company recently completed its first set of clinical trials and is now preparing to begin the second and final round. The studies, which involve subjects with diabetes, are being conducted by independent clinical investigators. According to Cygnus spokesperson Susan Snyder, the trials are expected to last at least through the first half of this year.—G.F.