Blood Glucose Monitoring Devices

For millions of Americans with diabetes, regular home testing of blood glucose levels is critical in controlling their disease.

"The most near-normal glucose patterns you can get will have a terrific long-term impact on how well people with diabetes do," says Steven Gutman, M.D., director of the division of clinical laboratory devices in FDA's Office of Device Evaluation. But he adds, "Tight control isn't easy because it requires multiple glucose measurements."

For many years, diabetics relied on home urine glucose testing to monitor blood sugar levels. But the method was not without drawbacks. Monitoring glucose levels via the urine is problematic for several reasons: First, blood glucose concentrations above which glucose appears in the urine vary widely among individuals, so the tests are not very reliable. Second, factors such as fluid or vitamin C intakes can influence test results. And third, negative tests can't distinguish between normal, low, and moderately high blood sugar levels.

By the late 1960s, manufacturers began introducing home blood glucose monitoring kits. These kits allowed diabetics to detect blood sugar levels by looking at color changes on a chemical test strip using a single drop of blood from a pricked finger. Portable meters that could electronically read the strip and provide immediate results came along in the late 1970s.

Although today's monitors are small, easier to use than early ones, and reasonably priced at between $50 and $100, they all require users to prick their fingers to provide a blood sample for testing. So diabetics were understandably enthusiastic when a noninvasive glucose sensor monitoring device was developed. It doesn't require a finger prick but instead uses infrared technology to measure blood glucose. But after reviewing data from the device's manufacturer, the Clinical Chemistry and Clinical Toxicology Devices Advisory Panel of FDA's Medical Devices Advisory Committee decided more data were needed to ensure the device's safety and effectiveness.

"The idea of being able to test yourself without a painful prick is very attractive. It would probably increase compliance because some patients simply don't want to prick their fingers," Gutman says. "It's a very promising technology. But you have to balance technology against performance."

Gutman said the criteria the company chose to deem the device successful--that 50 percent of readings agree with 20 percent of readings from the patient's finger-prick device--was not an appropriate target. The panel agreed that success should be defined as having 80 to 90 percent of values correlating to values obtained with finger-prick tests. So, the FDA advisory committee also recommended that the sponsor conduct more studies, doing them at multiple sites and involving more women who develop diabetes while pregnant and more children. Also, the committee suggested that the sponsor base the studies on specific study objectives related to performance claims, with the data sufficient to ensure safety and effectiveness.

Julio V. Santiago, M.D., an internist specializing in diabetes and a former member of FDA's Endocrine Advisory Committee, says, "It's an exciting new technology that diabetics could benefit from, so we were rooting for the company. But they failed to demonstrate that the device worked long term for home use."

Santiago says that current invasive finger-prick devices are very reliable, with accuracy within 15 percent of real measurements 80 to 90 percent of the time. Their biggest disadvantage is cost, since each test strip costs 50 cents, and several are often used in one day. A spokesman for Boehringer Mannheim Corp., Rick Naples, says the cost of test strips and lancets needed to perform self blood-glucose monitoring can average between $600 and $1,000 a year.

FDA Recognizes Need for Non-invasive Glucose Monitors

Gutman says FDA appreciates the need for noninvasive glucose monitors and is anxious to work with companies early in the development of these devices. The Center for Devices and Radiological Health has implemented an expedited review program for devices like noninvasive glucose monitors so items that may be in the interest of public health can be made available in an expedited way without compromising the devices' safety and effectiveness, he says. "Such expedited reviews are given precedence over routine reviews."

Gutman is optimistic about future approval of a noninvasive blood glucose monitoring kit for diabetics. "I'd be very disappointed if we don't eventually see a noninvasive model in the future," he says.

--A.H.

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