Elevated skin AGEs are biomarkers of diabetes, are highly correlated with the complications of diabetes, and predict future diabetic retinopathy and nephropathy. Individuals with diabetes accumulate skin AGEs faster than do individuals with normal glucose regulation. Until the recent development of novel noninvasive technology to measure AGEs, a punch biopsy was needed to quantify skin AGE levels. Spectroscopic measurement of dermal AGEs (SAGE) measures skin fluorescence caused by AGEs and provides a quantitative diabetes risk score. It does not require fasting, creates no biohazards, automatically compensates for subject-specific skin differences, and provides an immediate result.

This head-to-head evaluation in a naive population of 351 subjects compared results from FPG and A1C tests with results from testing with a noninvasive device that detects the fluorescence of skin AGEs.

The positive screening class was defined as subjects with 2-hour oral glucose tolerance test (OGTT) values of 140 mg/dL or greater (n = 84; prevalence, 23.9%). The performances of the noninvasive device, FPG, and A1C were evaluated for sensitivity and specificity using the OGTT results as the gold standard.

At the impaired fasting glucose threshold of FPG of 100 mg/dL, sensitivity of FPG was 58% and specificity was 77.4%. At that same specificity, the sensitivity for A1C testing was 63.8%, whereas the noninvasive testing sensitivity was 74.7%. The increase in sensitivity of the noninvasive device compared with both blood tests for detecting diabetes and prediabetes was statistically significant (P < .05).

"The noninvasive technology showed clinical performance advantages over both FPG and A1C testing," the authors write. "The sensitivity differential indicated that the noninvasive device is capable of identifying 28.8% more individuals in the OGTT-defined positive screening class than FPG testing and 17.1% more than A1C testing. The combination of higher sensitivity and greater convenience — rapid results with no fasting or blood draws — makes the device well suited for opportunistic screening."

Practice Pearls

• The SAGE technique is a noninvasive measure of skin fluorescence to detect glycation end products associated with diabetes risk.
• The sensitivity of the SAGE technique is higher than that of FPG and A1c for detection of type 2 diabetes and impaired glucose tolerance.

Diabetes Care. 2007;30:1120-1124.

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