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Imagine shining a light on a patient's forearm and, within a minute, detecting the presence of type 2 diabetes. The prospect may sound improbable, but a new technology may make it possible. Fluorescence spectroscopy works by identifying the presence of unusually high concentrations of advanced glycation end products (AGEs)—diabetes-related biomarkers—on the skin surface.
In early clinical trials, a 4.5-kg (10-lb) experimental device that employs fluorescence spectroscopy—the Scout DS—appears to more successfully diagnose diabetes based on AGEs than the existing screening methods of testing fasting plasma glucose (FPG) and glycated hemoglobin (A1C). And, perhaps just as significant, the Scout DS is more convenient for patients.
"There is a great need for a screening device that is noninvasive and can be used easily," says nurse practitioner Geralyn R. Spollett, MSN, ANP, CDE, associate director at Yale Diabetes Center at Yale School of Medicine in New Haven, Conn. "Even when given lab requests [for off-site blood draws], patients will not always follow through." That's likely because blood draws mean needles, and often fasting and additional appointments. Not so with the Scout DS.
VeraLight plans to submit data from its experiments with the device to the Food and Drug Administration (FDA) by the end of 2007, and anticipates a ruling by mid-2008. The company believes the product has applications beyond screening, such as assessing the risk of complications, but it hasn't carried out research in those areas yet.
But the device may have limitations. Some observers question the Scout DS's apparent inability to capture accurate readings for the entire patient population, particularly those with very dark pigmentation—a potential problem given the disproportionately high percentage of African-American adults with diabetes. Though the device's price has not been set, cost could be another stumbling block, particularly for small physician practices that would only use the device sporadically.
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PROMISING RESULTS
Of course, existing diagnostic tools are not perfect—as revealed when researchers led by John Maynard, MS, of VeraLight, and including Mark Robert Rohrscheib, MD, of University of New Mexico School of Medicine in Albuquerque, recently compared the screening effectiveness of the Scout DS with that of FPG and A1C among 351 participants. FPG's sensitivity was 58%; A1C's sensitivity came in at 63.8%; and sensitivity of the Scout DS was 74.7%.1
This is not the first time FPG's poor sensitivity has been demonstrated. Other research places its sensitivity at 40–60%, a factor that contributes to the widespread problem of late diabetes diagnosis.2 Because so many people are diagnosed well after the disease has developed, an estimated half of patients present with at least one irreversible complication at the time of diagnosis.3,4
VeraLight hopes to match its original findings in much larger-scale studies among people at risk for type 2 diabetes. Currently, researchers are conducting a multisite U.S. trial of the Scout DS on 1,700 subjects. Next, the product will undergo an even larger trial, performed at 20 U.S. sites and involving 5,400 subjects.
POTENTIAL DRAWBACKS
The Scout DS's diminished sensitivity with darker skin pigmentation may be its biggest hurdle, although a manufacturer's press release states that "the instrument compensates for skin pigmentation so that performance is not diminished by skin coloration."
VeraLight CEO David Van Avermaete acknowledges the experimental device has not been able to get an accurate reading on some black subjects, due to darker pigmentation, but contends this failure applies to "only a very small percentage of African Americans."
Van Avermaete says this obstacle would not limit the device's widespread use, but others aren't so sure, especially considering that 13.3% of U.S. black adults >20 years of age have diabetes, compared with 8.7% of U.S. white adults.5
"I'd like to see studies done that include a larger number of subjects with more pigmentation," says Robert Tanenberg, MD, director of the Diabetes and Obesity Center at East Carolina University in Greenville, N.C. He notes that the recently published study on Scout DS included only 11 black participants out of 351 study subjects.
The device also excludes some tattoo wearers. Van Avermaete explains that the lead in tattoos interferes with accurate readings. And the test is performed on the underside of patients' forearms, a popular spot for tattoos.
Tanenberg expresses concern that undetermined cost—and the uncertainty of whether insurance will cover the cost of the test for patients—could hinder adoption of the Scout DS in typical primary care settings.
But the device's fast-acting nature could appeal to large-scale operations. Van Avermaete envisions the system's being used in ambulatory care centers and by increasingly popular mobile health screening services.
Some see the Scout DS working well in other settings, too. "In a large HMO, this might be a very useful tool, or for public health nurses in rural communities, where they're seeing large numbers of patients, or for public health departments," Tanenberg says.
EXPANDED USES?
Ultimately, the system could be used as more than a purely diagnostic tool, its manufacturer says. AGEs, the diabetes-related biomarkers detected by the device, have been associated with diabetes complications involving the retinal vessels and peripheral nerves.6
"Only about 20% of primary care physicians have heard about AGEs," says VeraLight's Maynard, who along with Van Avermaete believes the instrument could be used to annually monitor patients' AGE levels to evaluate diabetes disease progression and development of related complications.
The company has not yet tested it for such uses, however; to date, it has focused trials strictly on the Scout DS's efficacy as a screening tool.
"It's an important technology," Tanenberg says. "But its
role—assuming that additional studies confirm its accuracy and
sensitivity in all given populations—still needs to be
determined." 
Footnotes
More information on VeraLight's Scout DS device for noninvasive screening for type 2 diabetes is available at www.veralight.com/wdocs/Scout%20DS%20Brochure,%2007Jun07.pdf.
References
2. Engelgau MM, Narayan KM, Herman WH: Screening for type 2 diabetes. Diabetes Care 23:1563–1580, 2000.[Abstract]
3. Harris MI, Eastman RC: Early detection of undiagnosed diabetes mellitus: A U.S. perspective. Diabetes Metab Res Rev 16: 230–236, 2001.
4. United Kingdom Prospective Diabetes Study Group: U.K. Prospective Diabetes Study 6: Complications in newly diagnosed type 2 diabetic patients and their association with different clinical and biochemical risk factors. Diabetes Res 13:1–11, 1990.[Medline]
5. National Diabetes Information Clearinghouse: National diabetes statistics: Total prevalence of diabetes by race/ethnicity among people aged 20 years or older, United States, 2005. NIH Publication No. 06-3892, November 2005. Available at http://diabetes.niddk.nih.gov/dm/pubs/statistics/index.htm#9. Accessed July 14, 2007.
6. Peppa M, Uribarri J, Vlassara H: Glucose, advanced glycation end
products, and diabetes complications: What is new and what works.
Clinical Diabetes 21:186–187, 2003.
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