Fluorescein dermofluorometry for the assessment of diabetic microvascular disease

Background/aims: Fluorescein dermofluorometry can be used to relate the upt ake of fluorescein in the skin to blood flow. We have characterized the upt ake of the dye by a wash-in time constant that is inversely proportional to the local blood flow. The purpose of this study was to explore the use of dermofluorometry in the assessment of patients with diabetic microvascular disease. Methods: Fluorescein dermofluorometry was performed in four groups of patie nts: non-diabetic control patients, diabetic control patients, diabetic pat ients with chronic foot ulcers, and diabetic patients with acute foot ulcer s. The outcomes of the patients with foot ulcers were documented 4-14 month s after participation. Following an intravenous injection of sodium fluores cein, the change in the fluorescein signal with time was continuously measu red at the plantar surface of the foot. Both the initial slope of the signa l and the wash-in time constant were calculated in each subject. Results: Significant differences in the wash-in time constant were found be tween diabetic and non-diabetic subjects and between diabetic subjects with and without foot ulcers. Of the eight patients with foot ulcers, two of th em did not display an early wash-out in the dermofluorometer signal and lat er both required amputations. Conclusion: The fuorescein wash-in time constant demonstrated better correl ation with the presence of diabetic microvascular disease than did the init ial slope of the signal. Differences in the wash-in time constants of non-d iabetic and diabetic subjects support the hemodynamic hypothesis for the de velopment of microvascular disease. The indication of early wash-out of the fluorescein signal may also be useful in the prediction of ulcer healing.