Dec. 6, 1999 (Washington) -- An advisory panel to the FDA unanimously recommended for approval a wristwatch-like device that measures a diabetic's blood sugar without requiring as many frequent, painful fingersticks. The GlucoWatch, as it's called, offers continuous glucose monitoring with a visual readout and a distinctive beep in case a patient's blood sugar rises or falls to a dangerous level.
However, the Clinical Chemistry and Toxicology Devices Panel also said on Monday the FDA should require an extensive patient education program with the device as well as post-market studies about its use as a detection tool for blood sugar fluctuations. GlucoWatch is meant to improve glucose control by detecting trends and patterns, but not replace blood sugar measurements obtained from traditional fingersticks.
Panelist Arlan Rosenbloom, MD, of the University of Florida, tells WebMD he finds the novel technology exciting, and a possible step toward an "automatic pancreas," which would only be possible with a continuous monitoring system. "It's a new tool with new information, and we just have to learn a lot more about it," says Rosenbloom. Currently, the device is indicated for those aged 18 and above, but a number of individuals testified at the meeting that GlucoWatch could and should be used for children, including an 11-year old diabetic who said he had invested in the company making the device.
Manufactured by Cygnus Inc. of Redwood City, Calif., the GlucoWatch was compared to the traditional needlestick measurements in 473 diabetic patients -- two-thirds with type 1, or the juvenile form of the disease, and the rest suffering from type 2, or adult-onset diabetes. The patients wore the wristwatch-like device at home for five days, and in four studies Cygnus collected 13,000 "paired data points" to evaluate the GlucoWatch vs. the fingerstick.
Also known as a "biographer," the noninvasive GlucoWatch is intended to provide automatic readings at the rate of three per hour for up to 12 hours. However, a three-hour warm-up period is required to acclimatize the device to a person's skin, followed by a single stick to calibrate the system. The GlucoWatch is paired with a sensing device that is taped on the wrist. The sensor contains discs with the enzyme glucose oxidase.
As glucose from the skin touches the discs, hydrogen peroxide is produced, releasing electricity in the process. A sensor picks up that minute electric current and compares it to the glucose measure previously established. The basic process is called reverse iontophoresis.
According to Russell Potts, PhD, one of the company researchers, 94% of the data collected fell within the acceptable accuracy ranges for determining blood sugar, although there was a variation in the numbers up to 21%.
Overall, hypoglycemia was detected about two-thirds of the time. As a safety measure, the device is set to register an alarm when a patient's blood sugar is still at a relatively high level to prevent a person from sinking into a dangerous episode of hypoglycemia.
Cygnus hopes the GlucoWatch will be particularly effective at measuring peaks or valleys in blood sugar that may not show up on an individual stick test -- for example, when a patient's blood sugar "crashes" during sleep.
Studies from the National Institutes of Health indicate that better control of glucose levels could have a major impact on diabetes-related complications including blindness, amputations, or kidney failure. It's estimated 16 million Americans suffer from the insulin-producing defect that interferes with a person's ability to metabolize sugar.
If approved, GlucoWatch would be available by prescription, and Cygnus promises to carry on an extensive provider and patient education effort, including an individual use plan as well as a video. Another diabetes self-monitoring device, the MiniMed, was approved in June, but it's considered more invasive.
FDA reviewers raised several concerns about the device, including its tendency to shut off early or fail to calibrate, as well as how precisely one could measure GlucoWatch's effectiveness given that about one-quarter of the readings were missing in a key study, according to the FDA's Kristen Meier, PhD.
The FDA's Jean Fourcroy, MD, also says the device has a "significant skin irritant effect," and about half of those in the study had some inflammatory reaction. The manufacturer advises shaving to prepare the skin better before using the GlucoWatch, and a company researcher says patients are unconcerned about the side effect.
While Cygnus has yet to set a price, the company says the watch itself could cost about $250, and the sensing device about $4. It would have to be replaced after 12 hours, and the watch could last up to five years. The FDA usually, but not always, follows the recommendations of its advisory panels.