This paper presents an evaluation of time-resolved fluorescence measurements on human skin for screening type 2 diabetes. In-vivo human skin was excited with a pulse diode at 375 nm and pulse width of 700 ps. Fluorescence decays were recorded at four different emission wavelengths 442, 460, 478 and 496 nm. Experiments were performed on various locations including the palms, arms, legs, and cheeks of a healthy Caucasian subject to test single-subject variability. The fluorescence decays obtained were modeled using a three-exponential decay. The variations in the lifetimes and amplitudes from one location to another were minimal except on the cheek. The study compares the fluorescent decays of 38 diabetic subjects and 37 nondiabetic subjects, with different skin complexions and of ages ranging from 6 to 85 years. The average lifetimes for nondiabetic subjects were 0.5, 2.6 and 9.2 ns with fractional amplitudes of 0.78, 0.18 and 0.03, respectively. The effects of average hemoglobin A1c (HbA1c) from the previous four years and diabetes duration were evaluated. While no significant differences between the fluorescence lifetimes of nondiabetic and diabetic subjects were observed, two of the fractional amplitudes were statistically different. Additionally, none of the six fluorescence parameters correlated with diabetes duration or HbA1c.One of the lifetimes as well as two of the fractional amplitudes differed between diabetic subjects with foot ulcers and nondiabetic subjects.

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