|Trends & Perspectives|
When it comes to blood glucose monitoring devices, manufacturers know that noninvasive sampling is the ultimate goal. The finger pricks associated with existing blood glucose testing technologies can be so painful that many patients do not use them as frequently as they should. "Noninvasive sampling is what the market is demanding," says Al Snitkof, chief technology officer at Hemadyne Inc. (White Plains, NY). The company that is first able to meet that market demand seems destined to achieve a commanding share of the $2-billion glucose monitoring market.
The race to develop and perfect noninvasive glucose monitoring technologies has been under way for years, but several companies now say that FDA product filings are either imminent or on the visible horizon. Cygnus (Redwood City, CA) recently announced the completion of a clinical study for its noninvasive blood glucose monitoring product, the GlucoWatch biographer. The company is now conducting two smaller follow-up studies, and intends to submit a premarket approval (PMA) application to FDA by June 1999. According to the company, FDA has indicated that its PMA is appropriate for an expedited review and may be approved within a year.
The GlucoWatch biographer is worn like a wristwatch and uses a disposable reverse iontophoresis pad to extract and measure glucose levels. After calibration with a standard blood glucose monitor, the device will sound an alarm if glucose levels get too high or too low. The device automatically takes up to three measurements per hour for 12 hours. It can store data for up to three months, and can be used to download previously collected data into a PC.
Prototype of the GlucoWatch biographer blood glucose monitoring system. Photo courtesy Cygnus.
Another emerging player in the race for a noninvasive monitor is Hemadyne, using a technology called real-time adaptive digital identification of optical chemical signatures, (RADIOCS). The company's system is designed to be painless, to require no supplies, and to have the ability to test multiple analytes. It scans a range of near-infrared (NIR) wavelengths to compare blood analytes with digitally stored reference samples. The device can collect 250,000 samples per second in a typical 6- to 9-second test.
Hemadyne's neural network is embedded on a chip. This system-on-chip (SOC) learns the optimal NIR wavelength needed to capture analyte signatures. "A feedback loop helps the unit adapt to any changes in blood and body chemistry from, for instance, food or drug metabolism during the measurement period. Device calibration is accomplished automatically within 2 seconds," says Snitkof.
Proprietary digital signal processing software and hardware allow the SOC to remove noise or artifacts from the optical chemical signatures of analytes being measured and to provide feedback to the neural network. Snitkof says Hemadyne's Hematrac monitor employing the RADIOCS technology is ready for clinical trials, and Hemadyne is awaiting FDA guidance on whether to file a 510(k) or a PMA.
SpectRx (Norcross, GA) also has a noninvasive blood glucose monitoring product in the R&D stages. According to SpectRx president and CEO Mark Samuels, the company's continous monitoring approach "offers the promise of providing glucose information without the pain associated with invasive penetration by needles, lancets, or implants."
Top: needle puncture versus fluid collection through laser-generated micropores.
Bottom: the SpectRx prototype.
Photo courtesy Spectrx
The SpectRx prototype works by collecting interstitial fluid (ISF) through micropores that are created by a laser in the dead surface layer of skin. ISF is the clear liquid found under the skin and contains concentrations of glucose similar to those found in blood. According to a study conducted by the company, glucose concentration in the ISF has a correlation to blood glucose readings of 92.5%. In the SpectRx study, that calibration remained consistent over a three-day period.
Despite the progress being made by these and other companies, however, it will be a while, before any such noninvasive technologies become commercially available. Even with the most optimistic of projections, FDA approval isn't expected for at least a year.
In the meantime, other companies are entering the lucrative diabetes-care market with their invasive, but reportedly less-painful monitors. Amira (Grass Valley, CA) recently won FDA approval for its Atlast device, a product that still uses a needle prick, but draws capillary blood from the forearm, leg, or other such area that has fewer and less-sensitive nerve endings than the finger. According to the company, Atlast was deemed painless by 90% of those who used it in clinical trials and product demonstrations. Karen Drexler, president of Amira, says the technology is "robust, real, and FDA approved. And we're entering the market with a feature that diabetic patients ask for most—painlessness."
Lasette from Cell Robotics International (Albuquerque) is a finger perforator that uses a laser beam to penetrate the skin and obtain a capillary blood sample, unlike traditional steel lancets that prick the skin. Patients experienced less immediate and residual pain using the Lasette, and the patients' fingers appeared to heal faster, according to Robert Bernstein, principal investigator for the Lasette clinical trial. FDA cleared the device for home use by prescription in December 1998.
While less painful than traditional finger-stick tests, these technologies are still invasive. Until the truly noninvasive devices are available, the companies that make them will benefit from the profitable diabetes-care market. How long they will be able to take advantage of this situation is up to the companies developing noninvasive sampling devices and FDA.