Skin autofluorescence (SAF) was measured in participants in order to determine Advanced Glycation Endproducts (AGEs) using the AGE Reader device. AGEs are glycated proteins or lipids as a result of exposure to sugars (the Maillard reaction). AGEs are associated with ageing and development of several chronic diseases such as diabetes, renal insufficiency, and cardiovascular disease.

The AGE Reader is a non-invasive monitoring device that uses ultra-violet light to excite autofluorescence in human skin tissue. It illuminates a skin surface of approximately 4 cm², guarded against surrounding light, using an excitation light source with a wavelength between 300 and 420 nm (peak intensity at ~ 370 nm). Emission light and reflected excitation light from the skin are measured with an internal spectrometer in the range 300–600 nm.
SAF is calculated by dividing the average emitted light intensity per nanometre in the range of 420–600 nm by the average excited light intensity per nanometre in the range 300–420 nm and multiplied by 100. SAF levels are expressed in arbitrary units and will increase or decrease per arbitrary unit (AU)¹⁾.

The AGE Reader was validated against skin biopsies. Skin autofluorescence (SAF) was measured in 46 diabetic patients and 46 control subjects, skin biopsies were obtained from 43 participants (n=13 type 1 diabetes, n=18 type 2 diabetes, n=12 controls). Skin fluorescence was measured at the arm and lower leg. Skin biopsies were obtained at the same site of the arm, and analysed for collagen-linked fluorescence (CLF) and specific AGE: pentosidine, NΣ-(carboxymethyl)-lysine (CML) and NΣ-(carboxyethyl)lysine (CEL)²⁾ Simple non-invasive assessment of advanced glycation endproduct accumulation. Diabetologia 47:1324-1330)).
Reliability was tested in 5 nursing students, aged 20 to 21. AF was measured using the triple measurments setting with three measurments of approximately 20 sec on three different lower arm sites. Cronbach’s alpha=0.974. Conclusion: reliability is very high³⁾.

In adult Lifelines participants, three measurements were made on the volar side of the forearm, 10 cm below the elbow, at room temperature.

Ca 9% of the measurements at baseline were excluded after quality control. Reasons for exclusion were:

• Use of sunscreen by participants on the day of measurement
• Calibration errors (i.e. dates on which all measurements of a single AGE-reader were deviant)
• Deviations in repeated measures within 1 participant

Details about the quality control of AGE-reader results can be obtain from Lifelines (on request).

1. van Waateringe et al. (2016) Lifestyle and clinical determinants of skin autofluorescence in a population-based cohort study. European Journal of Clinical Invertigation 46(5): 481-490
2. van Waateringe et al. (2017) Skin autofluorescence, a non-invasive biomarker for advanced glycation end products, is associated with the metabolic syndrome and its individual components. Diabetology & Metabolic Symdrome 9(1): 42
3. van Waateringe et al. (2017) The association between various smoking behaviors, cotinine biomarkers and skin autofluorescence, a marker for advanced glycation end product accumulation. Plos ONE 12(6): e0179330
4. Fokkens et al. (2018) Skin autofluorescence improves the Finnish Diabetes Risk Score in the detection of diabetes in a large population-based cohort: The LifeLines Cohort Study. Diabetes & Metabolism 44(5): 424-430
5. van Waaterine et al. (2018) Skin autofluorescence, a non-invasive biomarker for advanced glycation end products, is not related to the number of pregnancies. Journal of Diabetes 10(11): 899-901
6. van Waateringe et al. (2019) Skin autofluorescence predicts incident type 2 diabetes, cardiovascular disease and mortality in the general population. Diabetologia 62(2): 269-280