Non-invasive Measurement of Advanced Glycation End-products in the Skin

Number: 0841


Aetna considers the non-invasive measurement of advanced glycation end-products (AGEs) in the skin experimental and investigational because of insufficient evidence in the peer-reviewed literature.


Advanced glycation end-products (AGEs) are modifications of proteins or lipids that have become glycated and oxidized following exposure to aldose sugars; they form in-vivo in hyperglycemic environments and during aging.  Advanced glycation end-products contribute to the pathophysiology of vascular disease in diabetes through accumulation in the vessel walls, where they may perturb cell structure and function.  Advanced glycation end-products have also been hypothesized to play a role in atherosclerosis, acute ischemic stroke, and chronic kidney disease (Macsai, 2012; Tang et al, 2013).  A number of different therapies to inhibit AGEs are under investigation (Goldin et al, 2006).

Gerrits et al (2008) conducted noninvasive skin auto-fluorescence (SAF) in 973 type 2 diabetic patients through use of an autofluorescence reader.  After a mean follow-up period of 3.1 years, baseline SAF was significantly higher in patients who developed microvascular complications, neuropathy, or (micro)albuminuria, but not in patients who developed retinopathy.  This study was the first to observe SAF measurement as an independent predictor of development of microvascular complications in type 2 diabetes.

Hartog et al (2009) investigated whether SAF predicted graft loss following kidney transplantation.  They entrolled a total of 302 renal transplant recipients at a median time of 6.1 years post-transplant.  They followed the study population for 5.2 years for first occurrence of graft loss.  Skin auto-fluorescence predicted graft loss in a Cox regression multivariable analysis (hazard ratio [HR]: 1.83 [1.22 to 2.75], p = 0.003), adjusted for other identified risk-factors such as patient age, creatinine clearance, protein excretion, high sensitivity C-reactive protein, and human leukocyte antigen-DR mismatching.  The investigators concluded that SAF is an independent predictor of graft loss in kidney transplant recipients and that although SAF is not a direct measure of AGEs, the results support a hypothesis that accumulation of AGEs in renal transplant recipients contributes to the development of graft loss.

Smit et al (2010) describe SAF measurement as a noninvasive method of assessing accumulation of AGEs in tissue with low turnover metabolic memory and oxidative stress.  One device for measuring AGEs in tissue is the AGE  Reader®, which measures tissue accumulation of AGEs by means of fluorescence techniques.  It has a light source which illuminates the tissue of interest by exciting fluorescent moieties in the tissue, which will emit light with a different wavelength.  In the used wavelength band, the major contribution in fluorescence comes from fluorescent AGEs and therefore the emitted light is detected using a spectrometer.  Selective discrimination of specific AGEs can be obtained through use of particular technical adaptations including selection of specific wavelength and modulated or pulsed light sources, so that a more selective discrimination of specific AGEs can be obtained (Diagoptics, 2013).

Skin fluorescence was measured in 105 participants of the Pittsburgh Epdemiology of Diabetes Complications Study of Childhood-Onset type 1 diabetes, who had previously undergone electron beam tomograhy scanning for coronary artery calcification.  Study participants’ mean age and diabetes duration were 49 and 40 years, respectively. Measureable coronary artery calcification was found in 71 % of participants and univariately cross-sectionally associated with skin fluorescence.  However, this association was not maintained after age adjustment.  The authors also found that skin fluorescence was both univariately (p < 0.0001) and multi-variately ( p = 0.03) associated with coronary artery calcification severity.  The authors concluded that the relationship between skin fluorescence and coronary artery calcification appears stronger with more severe calcification, suggesting that skin fluorescence may be a useful marker of coronary artery calcificaiton and coronary artery disease risk and potentially may serve as a potential therapeutic target (Conway, 2010).

A study of 140 type 1 diabetic and 57 non-diabetic subjects was conducted to compare AGE accumulation in the skin of patients in a type 1 diabetic and non-diabetic population.  The study also assessed its association with disease duration and metabolic control.  The investigators found that mean AF in the diabetes group was 2.13 ± 0.55, which was significantly higher than in controls (AF 1.70 ± 0.27, p < 0.05).  A significant positive correlation between AF and patients’ age was found for the whole study population (p < 0.05).  A significant positive correlation was also found in diabetic subjects between AF and diabetes duration (p < 0.05) as well as between AF and hemoglobin A1c (HbA1c) levels (p < 0.05).  The authors concluded that autofluorescence measurement may be useful as a secondary method of assessing metabolic control as it reflects glycemic control over a longer period of time than that reflected by HbA1c levels (Samborski et al, 2011).

Beisswenger et al (2012) stated that although measurement of SAF has been promoted as a non-invasive technique to measure skin AGEs, the actual products quantified are uncertain.  They compared specific SAF measurements with analytically determined AGEs and oxidative biomarkers in skin collagen to determine if these measures are correlated with chronological aging and actinic exposure.  Skin autofluorescence was measured at 4 sites on the arms of 40 non-diabetic subjects.  They found poor correlation of AGE-associated fluorescence spectra with AGEs and oxidative products (OPs) in collagen, with only pentosidine correlating with fluorescence at 370(ex)/440(em)nm.  Thus, they concluded that SAF measurements at 370(ex)/440(em) nm and 335(ex)/385(em) nm, except for pentosidine, correlated poorly with glycated and oxidatively modified protein in human skin and do not reflect actinic modification.  A new fluorescence measurement (440(ex)/529(em) nm) appeared to reflect AGEs and OPs in skin.

Hofman et al (2012) noted that AGEs may be involved in aging and development of cardiovascular disease.  They further noted that “whether non-invasive measurement of AGE accumulation in the skin may reflect vessel function and vessel protein modification is unknown”.  The authors isolated collagen types I and III from the veins of 52 patients by proteolysis to analyze the AGE-modifications in the collagens extracted from residual bypass graft material.  The SAF reflected accumulation of AGEs in the body and the pulse wave velocity reflected vessel stiffness.  They measured SAF with an autofluorescence reader.  They noted that the collagen AGE autofluorescence in vein graft material increased with age and the pepsin digestible collagen fraction was significantly less modified in comparison to the collagenase digestible fraction.  Thus, the authors concluded that SAF and pulse wave velocity as non-invasive parameters significantly correlated with the AGE contained in graft material, making them strong predictors of vessel AGE modifications in patients with coronary artery disease.  However, the authors also stated that “whether the analysis of the SAF leads to an improvement of the risk stratification in patients suffering from cardiovascular disease has to be further tested”.

Macsai et al (2012) conducted a study to assess whether SAF is influenced by clinical and treatment characteristics in peritoneal dialysis (PD) patients.  Their cross-sectional study of 198 PD patients involved utilization of a specific AE Reader device.  The authors’ analysis revealed that patients’ age, current diabetes and icodextrine use significantly increased patients’ SAF values (p = 0.015, 0.012, and 0.005, respectively), thus illustrating that in this study group AGE exposure of PD patients with diabetes and on icodextrin solution is increased.  The authors noted that further investigation is required to determine whether this finding is due to the icodextrin itself or to a still unspecified clinical characteristic of PD populations treated with icodextrin.

Noordzij et al (2012) evaluated SAFs in patients with carotid artery stenosis with and without co-existing peripheral arery occlusive disease (PAOD) in 56 carotid artery stenosis and 56 age- and sex- matched healthy controls.  Skin autofluorescence was found to be higher in patients with carotid artery stenosis compared to the control group (mean 2.81 versus 2.46, p = 0.002).  The authors further noted that patients with carotid artery stenosis and PAOD had an even higher SAF than patients with carotid artery stenosis only (mean 3.29 versus 2.66, p = 0.003).  The investigators concluded that SAF is increased in patients with carotid artery stenosis and PAOD, and that the uni-variate and multi-variate associations of SAF with age, smoking, diabetes, renal insufficiency and PAOD suggested that increased SAF can be seen as an indicator of widespread atherosclerosis. 

Current American Association of Clinical Endocrinologists medical guidelines for clinical practice for developing a diabetes mellitus comprehensive care plan do not refer to advanced glycemic endpoints (Handelsman et al, 2011).  Although there have been recently published case-control, cross-sectional and case series studies on this topic, the breadth of evidence is such that non-invasive measurement of AGEs in the skin remains experimental and investigational at this time.

Chaudhri et al (2013) noted that SAF has been advocated as a quick non-invasive method of measuring tissue AGE, which have been reported to correlate with cardiovascular risk in the dialysis patient.  Most studies have been performed in patients from a single racial group, and these researchers wanted to look at the reliability of SAF measurements in a multi-racial dialysis population and whether results were affected by hemodialysis.  These investigators measured SAF 3 times in both forearms of 139 hemodialysis patients, pre-dialysis and 36 post-dialysis.  A total of 139 patients, 62.2 % male, 35.3 % diabetic, 59 % Caucasoid, mean age of 65.5 ± 15.2 years were studied.  Reproducibility of measurements between the 1st and 2nd measurements was very good (r(2 ) = 0.94, p < 0.001, Bland Altman bias 0.05, confidence limits -0.02 to 0.04).  However, SAF measurements were not possible in 1 forearm in 8.5 % Caucasoids, 25 % Far Asian, 28 % South Asians and 75 % African or Afro Caribbean (p < 0.001).  Mean SAF in the right forearm was 3.3 ± 0.74 arbitrary units (AU) and left forearm 3.18 ± 0.82 AU pre-dialysis, and post-dialysis there was a fall in those patients dialyzing with a left sided arterio-venous fistula (left forearm pre 3.85 ± 0.72 versus post 3.36 ± 0.55 AU, p = 0.012).  The authors concluded that although SAF is a relatively quick non-invasive method of measuring tissue AGE and measurements were reproducible, it was often not possible to obtain measurements in patients with highly pigmented skin.  To exclude potential effects of arterio-venous fistulae, the authors suggested that measurements be made in the non-fistula forearm pre-dialysis.

Hoffman et al (2013) stated that AGEs seem to be involved in aging as well as in the development of cardiovascular diseases.  During aging, AGEs accumulate in extracellular matrix proteins like collagen and contribute to vessel stiffness.  Whether non-invasive measurement of AGE accumulation in the skin may reflect vessel function and vessel protein modification is unknown.  These researchers analyzed the AGE-modifications in the collagens extracted from residual bypass graft material, the SAF reflecting the accumulation of AGEs in the body as well as the pulse wave velocity reflecting vessel stiffness.  Collagen types I and III (pepsin digestible collagen fraction) were isolated from the veins of 52 patients by proteolysis.  The residual collagen fraction was further extracted by collagenase digestion.  Collagen was quantified by hydroxyproline assay and AGEs by the AGE intrinsic fluorescence.  Skin autofluorescence was measured with an autofluorescence reader; pulse wave velocity with the VICORDER.  The collagen AGE autofluorescence in patient vein graft material increased with patient age.  The pepsin digestible collagen fraction was significantly less modified in comparison to the collagenase digestible fraction.  Decreasing amounts of extracted collagenase digestible collagen corresponded with increasing AGE autofluorescence.  Skin autofluorescence and vessel stiffness were significantly linked to the AGE autofluorescence of the collagenase digestible collagen fraction from graft material.  The authors concluded that SAF and pulse wave velocity as non-invasive parameters significantly correlated with the AGE contained in graft material and therefore are strong predictors of vessel AGE modifications in patients with coronary heart disease.  Moreover, they stated that whether the analysis of the SAF leads to an improvement of the risk stratification in patients suffering from cardiovascular disease has to be further tested.

Vouillarmet et al (2013) examined if AGEs measurement by SAF would be an additional marker for diabetic foot ulceration (DFU) management.  These researchers performed SAF analysis in 66 patients with a history of DFU prospectively included and compared the results with those of 84 control patients with diabetic peripheral neuropathy without DFU.  They then assessed the prognostic value of SAF levels on the healing rate in the DFU group.  Mean SAF value was significantly higher in the DFU group in comparison with the control group, even after adjustment for other diabetes complications (3.2 ± 0.6 arbitrary units versus 2.9 ± 0.6 arbitrary units; p = 0.001).  In the DFU group, 58 (88 %) patients had an active wound at inclusion.  The mean DFU duration was 14 ± 13 weeks.  The healing rate was 47 % after 2 months of appropriate foot care.  A trend for a correlation between SAF levels and healing time in DFU subjects was observed but was not statistically significant (p = 0.06).  The authors concluded that increased SAF levels are associated with neuropathic foot complications in diabetes; and use of SAF measurement to assess foot vulnerability and to predict DFU events in high-risk patients appears to be promising.

Llaurado et al (2014) examined the relationship between AGEs and arterial stiffness (AS) in subjects with type 1 diabetes without clinical cardiovascular events.  A set of 68 patients with type 1 diabetes and 68 age- and sex-matched healthy subjects were evaluated.  Advanced glycation end-products were assessed using serum concentrations of N-carboxy-methyl-lysine (CML) and using SAF; AS was assessed by aortic pulse wave velocity (aPWV), using applanation tonometry.  Patients with type 1 diabetes had higher serum concentrations of CML (1.18 versus 0.96 μg/ml; p = 0.008) and higher levels of SAF (2.10 versus 1.70; p < 0.001) compared with controls.  These differences remained significant after adjustment for classical cardiovascular risk factors.  Skin autofluorescence was positively associated with aPWV in type 1 diabetes (r = 0.370; p = 0.003).  No association was found between CML and aPWV.  Skin autofluorescence was independently and significantly associated with aPWV in subjects with type 1 diabetes (β = 0.380; p < 0.001) after adjustment for classical cardiovascular risk factors.  Additional adjustments for HbA1c, disease duration, and low-grade inflammation did not change these results.  The authors concluded that skin accumulation of autofluorescent AGEs is associated with AS in subjects with type 1 diabetes and no previous cardiovascular events.  They stated that these findings indicated that determination of tissue AGE accumulation may be a useful marker for AS in type 1 diabetes.

Yasuda et al (2015) evaluated the relationship between SAF, which reflects the accumulation of AGEs, and the severity of diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (T2DM).  A total of 67 eyes of 67 patients with T2DM were enrolled; 67 age-matched non-diabetic subjects served as controls.  Diabetic patients were classified by the severity of their DR: no DR (NDR), non-proliferative DR (NPDR), and proliferative DR (PDR).  Skin auto-fluorescence was measured with an auto-fluorescence reader.  Skin auto-fluorescence in the diabetes patients was significantly higher than in the controls (median 2.5 (interquartile range of 2.3 to 2.7) and 1.8 (1.6 to 2.3) AU, respectively, p < 0.001).  There was a statistically significant increase in SAF along with the increasing severity of DR (from NDR to NPDR: p = 0.034; NPDR to PDR: p < 0.01).  Logistic regression analysis revealed that SAF (odds ratio [OR], 17.2; p < 0.05) was an independent factor indicating the presence of PDR.  The authors concluded that SAF has an independent relationship with PDR in patients with T2DM.  They stated that SAF measurement with an auto-fluorescence reader is a non-invasive way to assess the risk of DR; SAF may, therefore, be a surrogate marker candidate for the non-invasive evaluation of DR.

Krul-Poel et al (2015) noted that SAF is a non-invasive measurement of AGE, which are suggested to be one of the major agents in the pathogenesis and progression of diabetes related cardiovascular complications.  Recently, low vitamin D status has been linked to the progression of T2DM and cardiovascular disease.  These researchers investigated the association between vitamin D status and SAF in patients with T2DM.  In this preliminary report, SAF was measured non-invasively with an AGE-reader in 245 patients with T2DM treated with lifestyle advice, metformin and/or sulphonylurea-derivatives.  All patients were randomly assigned to receive either vitamin D 50,000 IU/month or placebo for 6 months.  Skin auto-fluorescence was significantly higher in patients with a serum 25(OH)D less than 50 nmol/L compared to patients with a serum 25(OH)D greater than 75 nmol/L (2.81 versus 2.41; p < 0.001).  Mean serum 25(OH)D was 60.3 ± 23.4 nmol/L and was independently associated with SAF (β -0.006; p < 0.001).  Mean vitamin D increased from 60.8 to 103.6 nmol/L in the intervention group; however no effect was seen on accumulation of skin AGEs after 6 months compared to placebo.  The authors concluded that vitamin D status is independently associated with SAF in patients with well-controlled T2DM.  No effect was seen on the amount of skin AGEs after a short period of 6 months vitamin D supplementation.  They stated that further research with longer follow-up and measurement of circulating AGE is needed to elucidate the causality of the association.

Banser et al (2016) stated that AGEs are considered major contributors to microvascular and macrovascular complications in adult patients with diabetes mellitus.  Advanced glycation end-products can be measured non-invasively with SAF.  These investigators determined SAF values in children with T1DM and studied correlations between SAF values and HbA1c and mean HbA1c over the year prior to measurement.  In children with T1DM, SAF values were measured using the AGE Reader.  Laboratory and anthropometric values were extracted from medical charts.  Correlations were studied using Pearson's correlation coefficient.  Multi-variable linear regression analysis was conducted to evaluate the effect of multiple study parameters on SAF values. The mean SAF value was 1.33 ± 0.36 arbitrary units (AU) in children with T1DM (n = 144); SAF values correlated positively with HbA1c measured at the same time (r = 0.485; p < 0. 001), mean HbA1c over the year prior to measurement (r = 0.578; p < 0.001), age (r = 0.337; p < 0.001), duration of T1DM (r = 0.277; p = 0.001), serum triglycerides (r = 0.399; p < 0.001), and total cholesterol (r = 0.352; p = 0.001); SAF values were significantly higher in patients with non-white skin (1.56 versus 1.27 AU, respectively, p = 0.001).  The authors concluded that in children with T1DM, SAF values correlated strongly with single HbA1c and mean HbA1c, making the non-invasive SAF measurement an interesting alternative to provide information about cumulative hyperglycemic states.  Moreover, they stated that to determine the value of SAF measurement in predicting long-term microvascular and macrovascular complications, further prospective follow-up studies are needed.

In a pilot study, Meertens and colleagues (2016)
  1. explored the reliability of SAF as an index of tissue AGEs in patients in the intensive care unit (ICU),
  2. compared its levels to healthy controls,
  3. described the time course of AGEs and influencing factors during ICU admission, and
  4. examined their association with disease severity, outcome, and markers of oxidative stress and inflammation.
Serum N"-(carboxyethyl)lysine (CEL), CML, SAF, and soluble RAGE (sRAGE) were serially measured for a maximum of 7 days in critically ill ICU patients with multi-organ failure and compared to age-matched healthy controls.  Correlations with (changes in) clinical parameters of disease severity, low-density lipoprotein (LDL) dienes, and C-reactive protein (CRP) were studied and survival analysis for in-hospital mortality was performed.  A total of 45 ICU patients (age of 59 ± 15 years; 60 % male), and 37 healthy controls (age of 59 ± 14 years; 68 %) were included.  Skin AF measurements in ICU patients were reproducible (CV right-left arm: 13 %, day-to-day: 10 %), with confounding effects of skin reflectance and plasma bilirubin levels.  Skin AF was higher in ICU patients versus healthy controls (2.7 ± 0.7 versus 1.8 ± 0.3 au; p < 0.001).  Serum CEL (23 ± 10 versus 16 ± 3 nmol/gr protein; p < 0.001), LDL dienes (19 (15 to 23) versus 9 (8 to 11) μmol/mmol cholesterol; p < 0.001), and sRAGE (1,547 (998 to 2,496) versus 1,042 (824 to 1,388) pg/ml; p = 0.003) were significantly higher in ICU patients compared to healthy controls, while CML was not different (27 (20 to 39) versus 29 (25 to 33) nmol/gr protein).  While CRP and LDL dienes decreased significantly, SAF and serum AGEs and sRAGE did not change significantly during the first 7 days of ICU admission; CML and CEL were strongly correlated with the sequential organ failure assessment (SOFA) scores and CML above the median at baseline was associated with increased risk for mortality (HR 3.3 (1.3 to 8.3); p = 0.01).  All other markers did not correlate with disease severity and did not predict mortality.  The authors concluded that the findings of this study demonstrated that markers for the AGE-RAGE axis were elevated in critically ill patients compared to healthy controls but remained stable for at least 7 days despite clearly fading inflammation and oxidative stress.  They stated that circulating AGEs may be associated with disease severity and outcome; and further research should be conducted to elucidate the role of the AGE-RAGE axis in the exaggerated inflammatory response leading to multi-organ failure and death, and whether or not this may be a target for treatment.

Schutte and associates (2016) examined the association of SAF with rate of kidney function decline in a cohort of patients with peripheral artery disease (PAD).  These researchers performed a post-hoc analysis of an observational longitudinal cohort study.  They included 471 patients with PAD, and SAF was measured at baseline.  Primary end-point was rate of estimated glomerular filtration rate (eGFR) decline.  Secondary end-points were incidence of eGFR less than 60 and less than 45 ml/min/1.73 m(2) and rapid eGFR decline, defined as a decrease in eGFR of greater than 5 ml/min/1.73 m(2)/y.  During a median follow-up of 3 years, the mean change in eGFR per year was -1.8 ± 4.4 ml/min/1.73 m(2)/year.  No significant difference in rate of eGFR decline was observed per 1 arbitrary unit increase in SAF (-0.1 ml/min/1.73 m(2)/y; 95 % confidence interval [CI]: -0.7 to 0.5; p = 0.8).  Analyses of the secondary end-points showed that there was an association of SAF with incidence of eGFR less than 60 and less than 45 ml/min/1.73 m(2) (HR, 1.54; 95 % CI: 1.13 to 2.10; p = 0.006 and HR, 1.76; 95 % CI:, 1.20 to 2.59; p = 0.004, respectively), but after adjustment for age and sex, significance was lost.  There was no association of SAF with rapid eGFR decline.  The authors concluded that in this cohort of patients with PAD, SAF levels did not predict the rate of kidney function decline during follow-up in this study.

Hangai and colleagues (2016) evaluated the association of tissue AGE, assessed using SAF, with coronary artery calcification in Japanese subjects with type 2 diabetes.  A total of 122 Japanese subjects with type 2 diabetes enrolled in this cross-sectional study underwent multi-slice computed tomography for total coronary artery calcium scores (CACS) estimation and examination with a SAF reader; SAF positively correlated with age, sex, diabetes duration, pulse wave velocity, systolic blood pressure (SBP), serum creatinine, and CACS.  In addition, SAF results negatively correlated with body mass index (BMI), eGFR, and serum C-peptide concentration.  According to multi-variate analysis, age and SBP showed strong positive correlation and eGFR showed negative correlation with SAF values.  Multiple linear regression analyses revealed a significant positive correlation between SAF values and logCACS, independent of age, sex, diabetes duration, HbA1c, BMI, carotid intima-media thickness (IMT), and BP.  However, SAF showed no association with serum levels of AGE, such as CML and 3-deoxyglucosone.  The authors concluded that SAF results positively correlated with CACS in Japanese subjects with type 2 diabetes.  They stated that these findings indicated that AGE plays a role in the pathogenesis of diabetic macro-vascular disease; and measurement of SAF values may be useful for assessing the severity of diabetic complications in Japanese subjects.

Rajaobelina and co-workers (2017) examined if the accumulation of AGEs measured by SAF was associated with signs of diabetic peripheral neuropathy (DPN) and to sensitivity, pain, motor and autonomic function 4 years later in patients with type 1 diabetes.  At baseline, 188 patients (age of 51 years, diabetes duration of 22 years) underwent SAF measurement using the AGE Reader.  Four years later, signs of DPN were defined as the presence of neuropathic pain and/or feet sensory loss or foot ulceration.  Neurological tests were systematically performed: vibration perception threshold by neuro-esthesiometry, neuropathic pain by the Douleur Neuropathique en 4 Questions score, muscle strength by dynamometry and electrochemical skin conductance.  Multi-variate analyses were adjusted by age, sex, height, BMI, tobacco, HbA1c , diabetes duration, eGFR and albumin excretion rate.  At the 4-year follow-up, 13.8 % of patients had signs of DPN.  The baseline SAF was higher in those with signs of DPN (2.5 ± 0.7 versus 2.1 ± 0.5 arbitrary units (AU), p < 0.0005).  In the multi-variate analysis, a 1 SD higher SAF at baseline was associated with an increased risk of signs of neuropathy (OR = 2.68, p = 0.01).  All of the neurological tests were significantly altered in the highest quartile of the baseline SAF (greater than 2.4 AU) compared with the lowest quartiles after multi-variate adjustment.  The authors concluded that this non-invasive measurement of SAF may have a value for DPN in type 1 diabetes and a potential clinical utility for detection of DPN.

Yamanaka and co-workers (2016) noted that although the accumulation of AGEs of the Maillard reaction in the body is reported to increase with aging and is enhanced by the pathogenesis of lifestyle-related diseases such as diabetes, routine measurement of AGEs is not applied to regular clinical diagnoses due to the lack of conventional and reliable techniques for AGEs analyses.  In the present study, a non-invasive AGEs measuring device was developed and the association between skin AGEs and diabetic complications was evaluated.  To clarify the association between the duration of hyperglycemia and accumulation of skin fluorophores, diabetes was induced in mice by streptozotocin.  As a result, the fluorophore in the auricle of live mice was increased by the induction of diabetes.  Subsequent studies (168 subjects -- 82 subjects with T2DM and 86 subjects without T2DM) revealed that the fingertip of the middle finger in the non-dominant hand is suitable for the measurement of the fluorescence intensity by the standard deviation value.  Furthermore, the fluorescence intensity was increased by the presence of diabetic microvascular complications.  The authors concluded that the findings of this study suggested that the measurement of fluorescence intensity on fingertip is useful for predicting diabetic microvascular complications; this study provided the first evidence that the measurement of fluorescence intensity on the fingertip plays an important role in the early diagnosis and may prevent the pathogenesis of lifestyle-related diseases.

In a cross-sectional analysis, van Waateringe and colleagues (2017) examined the association between SAF and the presence of metabolic syndrome (MetS) as well as its individual components in a general population.  This study included 78,671 non-diabetic subjects between 18 and 80 years of age who participated in the LifeLines Cohort Study and had SAF measurement obtained non-invasively using the AGE Reader.  MetS was defined according to the revised NCEP ATP III criteria.  Students unpaired t-test was used to test differences between groups.  Both logistic and linear regression analyses were performed in order to test associations between the individual MetS components and SAF.  Subjects with MetS had higher SAF (2.07 ± 0.45 AU) compared to individuals without MetS (1.89 ± 0.42 AU) (p < 0.001).  There was a positive association between the number of MetS components and higher SAF Z-scores (p < 0.001).  Individuals in the highest SAF tertile had a higher presence of MetS (OR 2.61; 95 % CI: 2.48 to 2.75) and some of the individual components compared to subjects in the lowest SAF tertile.  After correction for age, gender, creatinine clearance, HbA1c and smoking status, only elevated BP and low HDL cholesterol remained significantly associated with higher SAF (p = 0.002 and p = 0.001, respectively).  The authors concluded that SAF was associated with the presence of MetS and some of its individual components.  In addition, increasing SAF Z-scores were observed with a higher number of MetS components.  Moreover, they stated that prospective studies are needed to establish whether SAF can be used as an (additional) screening tool to predict both cardiovascular disease and T2DM in high-risk populations.

Da Moura and associates (2017) noted that SAF has been demonstrated to be a biomarker of cumulative skin AGEs and potentially may be a better predictor for the development of chronic complications and mortality in diabetes than glycated hemoglobin A1c.  However, there are several confounding factors that should be assessed prior to its broader application: these include presence of other fluorescent compounds in the skin that might be measured (e.g., fluorophores), skin pigmentation and use of skin creams.

Franca and colleagues (2017) noted that chronic kidney disease (CKD) is associated with high morbidity and mortality rates, main causes related with cardiovascular disease (CVD) and bone mineral disorder (CKD-BMD).  Uremic toxins, as AGEs, are non-traditional cardiovascular risk factor and play a role on development of CKD-BMD in CKD.  The measurement of SAF is a non-invasive method to assess the level of AGEs in tissue, validated in CKD patients.  In a pilot study, these researchers analyzed AGEs measured by SAF levels (AGEs-SAF) and its relations with CVD and BMD parameters in hemodialysis (HD) patients.  A total of 20 prevalent HD patients (HD group) and healthy subjects (control group, n = 24), performed biochemical tests and measurements of anthropometric parameters and AGEs-SAF.  In addition, HD group performed measurement of intact parathyroid hormone (iPTH), trans-thoracic echocardiogram (TTE) and radiographies of pelvis and hands for vascular calcification score.  AGEs-SAF levels were elevated both in HD and control subjects ranged according to the age, although higher at HD than control group.  Single high-flux HD session did not affect AGEs-SAF levels.  AGEs-SAF levels were not related to ventricular mass, interventricular septum or vascular calcification in HD group.  AGEs-SAF levels were negatively associated with serum iPTH levels.  The authors concluded that this study detected a negative correlation of AGEs-SAF with serum iPTH, suggesting a role of AGEs on the pathophysiology of bone disease in HD prevalent patients.  The nature of this relation and the clinical application of this non-invasive methodology for evaluation AGEs deposition must be confirmed and clarified in future studies.  The authors stated that this pilot study had several drawbacks.  Potential influences of ethnicity and diet limited definitive conclusions.  In addition, these investigators did not perform AGEs analysis on serum or bone histo-morphometric studies.

In a multi-center study, Stirban and associates 92018) examined if SAF correlated with measures of diabetic peripheral neuropathy (DPN).  A total of 497 consecutive individuals with diabetes mellitus were studied.  Forearm SAF was measured using the AGE Reader (Groningen, The Netherlands); DPN was assessed using the Toronto Clinical Neuropathy Score (TCNS), the Neuropathy Symptoms Score (NSS) and the Neuropathy Disability Score (NDS).  According to the TCNS, SAF (arbitrary units - AU) was increased in individuals with DPN (TCNS greater than 5): 2.59 ± 0.56 AU compared with those without DPN (TCNS less than or equal to 5): 2.45 ± 0.53 AU, (p = 0.04) and significantly increased with the severity of DPN (p = 0.028).  Higher SAF was detected in individuals with neuropathic deficits (NDS greater than 2): 2.58 ± 0.56 AU versus those without deficits (NDS less than or equal to 2): 2.45 ± 0.53 AU, (p = 0.009) as well as in individuals with symptoms (NSS greater than 2): 2.54 ± 0.56 AU versus those without symptoms (NSS less than or equal to 2): 2.40 ± 0.47 AU, (p = 0.022).  The authors concluded that accumulation of AGE in skin was increased in individuals with DPN and progressed with the severity of DPN.  They sated that SAF measurement might help in identifying subjects at high risk for having DPN.  The findings need to be validated by further investigations.

Table: CPT Codes / HCPCS Codes / ICD-10 Codes
Code Code Description

Information in the [brackets] below has been added for clarification purposes.   Codes requiring a 7th character are represented by "+":

ICD-10 codes not covered for incidations listed in the CPB (not all inclusive):

E08.00 - E13.9 Diabetes mellitus

The above policy is based on the following references:

  1. Goldin A, Beckman, JA, Schmidt AM, Creager MA. Advanced glycation end products: Sparking the development of diabetic vascular injury. Circulation. 2006;114:597-605.
  2. Gerrits EG, Lutgers HL, Kleefstra N, et al. Skin autofluorescence: a tool to identify type 2 diabetic patients at risk for developing microvascular complications. Diabetes Care. 2008;31(3):517-521.
  3. Hartog JW, Gross S, Oterdoom LH, et al. Skin-autofluorescence is an independent predictor of graft loss in renal transplant recipients. Transplantation. 2009;87(7):1069-1077.
  4. Conway B, Edmundowicz D, Matter N, et al. Skin fluorescence correlates strongly with coronary artery calcification severity in type 1 diabetes. Diabetes Technol Ther. 2010;12(5):339-345.
  5. Smit AJ, Gerrits EG. Skin autofluorescence as a measure of advanced glycation endproduct deposition: a novel risk marker in chronic kidney disease. Curr Opin Nephrol Hypertens. 2010;19(6):527-533.
  6. Handelsman Y, Mechanick, JI, Blonde, L, et al. American Association of Clinical Endocrinologists medical guidelines for clinical practice for developing a diabetes mellitus comprehensive care plan. Endocrine Practice. 17(Suppl 2); March/April, 2011.
  7. Samborski P, Naskręt D, Araszkiewicz A, et al. Assessment of skin autofluorescence as a marker of advanced glycation end product accumulation in type 1 diabetes. Pol Arch Med Wewn. 2011;121(3):67-72.
  8. Beisswenger PJ, Howell S, Mackenzie T, et al. Two fluorescent wavelengths, 440(ex)/520(em) nm and 370(ex)/440(em) nm, reflect advanced glycation and oxidation end products in human skin without diabetes. Diabetes Technol Ther. 2012;14(3):285-292.
  9. Hofmann B, Adam AC, Jacobs K, et al. Advanced glycation end product associated skin autofluorescence: A mirror of vascular function? Exp Gerontol. 2013;48(1):38-44.
  10. Mácsai E. Skin autofluorescence measurement in the clinical practice of diabetology and nephrology. Orv Hetil. 2012 Oct 21;153(42):1651-1657.
  11. Mácsai E, Benke A, Cseh A, Vásárhelyi B. Factors influencing skin autofluorescence of patients with peritoneal dialysis. Acta Physiol Hung. 2012;99(2):216-222.
  12. Noordzij MJ, Lefrandt JD, Loeffen EA, et al.Skin autofluorescence is increased in patients with carotid artery stenosis and peripheral artery disease. Int J Cardiovasc Imaging. 2012;28(2):431-438.
  13. Diagoptics, Inc. Detailed information about advanced glycation endproducts, the AGE measurement and the clinical validation. Groningen, The Netherlands: Diagoptics; 2013. Available at: Accessed January 8, 2013.
  14. Tang SC, Wang YC, Li YI, et al. Functional role of soluble receptor for advanced gycation end products in stroke. Arterioscler Thromb Vasc Biol. 2013;33(3):585-594.
  15. Chaudhri S, Fan S, Davenport A. Pitfalls in the measurement of skin autofluorescence to determine tissue advanced glycosylation content in haemodialysis patients. Nephrology (Carlton). 2013;18(10):671-675.
  16. Hofmann B, Adam AC, Jacobs K, et al. Advanced glycation end product associated skin autofluorescence: A mirror of vascular function? Exp Gerontol. 2013;48(1):38-44.
  17. Vouillarmet J, Maucort-Boulch D, Michon P, Thivolet C. Advanced glycation end products assessed by skin autofluorescence: A new marker of diabetic foot ulceration. Diabetes Technol Ther. 2013;15(7):601-605.
  18. Llaurado G, Ceperuelo-Mallafre V, Vilardell C, et al. Advanced glycation end products are associated with arterial stiffness in type 1 diabetes. J Endocrinol. 2014;221(3):405-413.
  19. Yasuda M, Shimura M, Kunikata H, et al. Relationship of skin autofluorescence to severity of retinopathy in type 2 diabetes. Curr Eye Res. 2015;40(3):338-345.
  20. Krul-Poel YH, Agca R, Lips P, et al. Vitamin D status is associated with skin autofluorescence in patients with type 2 diabetes mellitus: A preliminary report. Cardiovasc Diabetol. 2015;14:89.
  21. Banser A, Naafs JC, Hoorweg-Nijman JJ, et al. Advanced glycation end products, measured in skin, vs. HbA1c in children with type 1 diabetes mellitus. Pediatr Diabetes. 2016;17(6):426-432.
  22. Meertens JH, Nienhuis HL, Lefrandt JD, et al. The course of skin and serum biomarkers of advanced glycation endproducts and its association with oxidative stress, inflammation, disease severity, and mortality during ICU admission in critically ill patients: Results from a prospective pilot study. PLoS One. 2016;11(8):e0160893.
  23. Schutte E, de Vos LC, Lutgers HL, et al. Association of skin autofluorescence levels with kidney function decline in patients with peripheral artery disease. Arterioscler Thromb Vasc Biol. 2016;36(8):1709-1714.
  24. Hangai M, Takebe N, Honma H, et al. Association of advanced glycation end products with coronary artery calcification in Japanese subjects with type 2 diabetes as assessed by skin autofluorescence. J Atheroscler Thromb. .  2016;23(10):1178-1187.
  25. Rajaobelina K, Farges B, Nov S, et al. Skin autofluorescence and peripheral neuropathy four years later in type 1 diabetes. Diabetes Metab Res Rev. 2017;33(2). 
  26. Yamanaka M, Matsumura T, Ohno R, et al. Non-invasive measurement of skin autofluorescence to evaluate diabetic complications. J Clin Biochem Nutr. 2016;58(2):135-140.
  27. van Waateringe RP, Slagter SN, van Beek AP, et al. Skin autofluorescence, a non-invasive biomarker for advanced glycation end products, is associated with the metabolic syndrome and its individual components. Diabetol Metab Syndr. 2017;9:42.
  28. Da Moura Semedo C, Webb M, Waller H, et al. Skin autofluorescence, a non-invasive marker of advanced glycation end products: Clinical relevance and limitations. Postgrad Med J. 2017;93(1099):289-294.
  29. Franca RA, Esteves ABA, Borges CM, et al. Advanced glycation end-products (AGEs) accumulation in skin: Relations with chronic kidney disease-mineral and bone disorder. J Bras Nefrol. 2017;39(3):253-260.
  30. Stirban AO, Bondor CI, Florea B, et al. Skin autofluorescence: Correlation with measures of diabetic sensorimotor neuropathy. J Diabetes Complications. 2018;32(9):851-856.