MANY diabetics have to endure frequent, painful finger pricks to monitor their blood sugar levels. But soon just a single prick of the finger will be enough to calibrate a watch-like monitor that can measure blood sugar levels non-invasively throughout the day.
Called the GlucoWatch, the $300 device, which is close to achieving final approval by the US Food and Drug Administration, could be in production by the end of this year. Diabetes experts believe the watch will revolutionise the prospects for diabetics. Frequent blood sugar monitoring helps detect the excessively high or low blood sugar levels that lead to complications such as blindness, kidney failure and nerve damage. But many diabetics find it painful and inconvenient to check their blood sugar more than once or twice a day, so they are unaware of when they could be in danger.
The GlucoWatch, which was developed by Cygnus of Redwood City, California, sits on top of a disposable gel disc that contains the same enzyme used to measure glucose levels in home monitors. Instead of testing the blood directly, the watch draws glucose from the body into the disc using a tiny electric current flowing between two terminals beneath the watch body. As the current passes through the skin, charged molecules migrate towards the electrodes (see Diagram). Glucose molecules, although uncharged, get swept up by this ion flow and are dragged across the skin to the gel disc by the cathode.
After putting on the GlucoWatch you have to wait for three hours while a new gel pad hydrates and reaches equilibrium with the skin. After this "warm-up" period, you calibrate the device using a glucose level taken from a standard finger-prick test. After that, the watch measures glucose levels every 20 minutes for a 12-hour period. If levels go too low or too high, it sounds a warning beep.
"It's data that's never been available before," says Steven Edelman, a diabetes specialist at the School of Medicine at the University of California, San Diego. Edelman, a diabetic who has worn the GlucoWatch several times, says continuous monitoring revealed that his blood levels fell dangerously low at night while he slept. "I really learned a tremendous amount," he says.
Cygnus expects the FDA to approve the GlucoWatch as a supplement to current monitoring methods, and to advise users to perform a traditional finger-prick test before injecting insulin. Satish Garg of the University of Colorado Health Sciences Center in Denver says: "That's not real life." He worries that diabetics will base their insulin dose on the GlucoWatch alone.
Garg also fears that doctors may provide it to young children with diabetes, even though it has only been tested in adults. "This is a major concern," agrees Cygnus vice-president Neil Ackerman, who says the company wants to test the device in children as quickly as possible.
Author: Nell Boyce, Washington DC
New Scientist issue: 27th March 2000
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