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U.S. Food and
Drug Administration
FDA Consumer magazine
May-June 2001
Table of Contents
By Raymond Formanek Jr.
The Food and Drug Administration has approved a wristwatch-like device designed to continuously monitor blood glucose levels in adults with diabetes to detect trends, track patterns and improve care.
The device, called the GlucoWatch Biographer, made by Cygnus, Inc., of Redwood City, Calif., is intended to be used with existing monitoring devices that use blood obtained through finger pricks to measure blood glucose. It is available only by prescription for adults ages 18 and older.
Diabetes is a group of chronic diseases characterized by the body's inability to produce or properly use insulin, a hormone that helps maintain normal levels of sugar (glucose) in the blood. Insulin is needed to convert sugar, starches and other food into energy. The hormone acts as a key that unlocks cells to allow glucose to enter. In diabetes, glucose that cannot be utilized builds up in the blood.
There is no cure for diabetes, and blood glucose monitoring is a key component in diabetes treatment and management. Consistently high blood sugar levels can, over time, lead to health complications such as blindness, kidney disease, heart disease, and nerve damage.
Diabetes is a leading cause of death in the United States and complications linked to poor control of blood glucose levels result in nearly $100 billion in medical costs annually, according to the National Institute of Diabetes and Digestive and Kidney Diseases.
People with Type 1 diabetes, whose pancreases no longer produce insulin, must inject insulin to control the levels of glucose in the blood. Frequent tests (several times a day) using blood obtained from finger pricks are required to maintain good blood sugar control. Those with Type 2 diabetes, whose pancreases don't make enough insulin or whose bodies don't use insulin properly, often control their diabetes through medication, exercise, diet, and sometimes insulin injections. They also must test their glucose levels to ensure good blood sugar control. An estimated 90 percent to 95 percent of the 16 million people in the United States with diabetes have Type 2, which generally develops after age 40.
The GlucoWatch is worn much like a wristwatch. A small electrical current from the device works to extract a tiny amount of fluid through the skin. A thin plastic sensor on the back of the watch measures glucose levels using this fluid--instead of blood--every 20 minutes for 12 hours. The device sounds an alarm if a person's glucose reaches dangerously high or low levels.
"New technology for monitoring glucose levels in people with diabetes is moving ahead rapidly, and the FDA has been working with a number of companies to help bring it to market," says Bernard A. Schwetz, D.V.M., Ph.D., Acting Principal Deputy Commissioner of Food and Drugs. "The GlucoWatch is one of the first steps in developing new products that may one day completely eliminate the need for daily finger-prick tests."
Clinical studies conducted by the manufacturer indicated that GlucoWatch measurements generally were consistent with results from the traditional finger-prick blood tests. However, the results differed by more than 30 percent up to a quarter of the time. The GlucoWatch was less effective at detecting very low glucose levels (hypoglycemia) than it was at detecting very high levels (hyperglycemia). In addition, the device would not measure blood sugar at all if a person's arm was too sweaty. The device also caused mild to moderate skin irritation in at least 50 percent of those involved in the studies.
"This type of device is a significant first step in a new direction in the monitoring of blood glucose levels," says Christopher D. Saudek, M.D., director of the Comprehensive Diabetes Center at Johns Hopkins University and president-elect of the American Diabetes Association. "Continuous and extended monitoring of blood glucose levels allows physicians to see patterns that are unobtainable with single-test monitoring. It will be important to gain experience, however, to find out the accuracy and reliability of these new devices in everyday situations."
Because of the potential for error, physicians and people with diabetes should never use a single GlucoWatch reading alone to make changes in insulin dosages. Instead, GlucoWatch results should be interpreted with several sequential readings over time and always checked against a device that uses a finger prick to determine blood sugar levels before taking action.
The device, approved on March 22, was studied in adults 18 and older in both clinical and home settings. The studies generated 19,000 glucose readings from 1,400 devices over 25,000 hours of use. Some 129 patients participated in the home study, which most closely reflected real-life use. The device was not tested in children.
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