Performance characteristics and clinical utility of an enzymatic method for the measurement of glycated albumin in plasma

Prevalence of poor glycemic control and the monitoring utility of glycated albumin among diabetic patients attending clinic in tertiary hospitals in Dodoma, Tanzania: A cross-sectional study protocol

The burden of diabetes is rising in developing countries, and this is significantly linked to the increasing prevalence of poor glycemic control. The cost of glycated haemoglobin (HbA1c) testing is a barrier to timely glycemic assessments, but newer tests such as glycated albumin may be cheaper and tempting alternatives. Additional research must ascertain if glycated albumin (GA) can act as a viable supplement or alternative to conventional HbA1c measurements for glycemic control in diabetic individuals. GA as a biomarker is an emerging area of interest, particularly for those who display unreliable HbA1c levels or cannot afford the test. This study aims to investigate the prevalence of poor glycemic control in outpatient diabetic patients and the utility of glycated albumin in this population's monitoring of glycemic control. Method. A cross-sectional study of 203 diabetic patients will be conducted at the Dodoma Regional Referral Hospital and Benjamin Mkapa Hospital from August 1st, 2023, to August 31st, 2024. Patients diagnosed with diabetes mellitus for over six months will be screened for eligibility. Informed consent, history, clinical examination, and voluntary blood sample collection will be obtained from all eligible patients. Glycated Albumin levels will be obtained from the same blood samples collected. The glycemic status of all patients will be defined as per HbA1c, and a level of greater than 7% will considered as a poor control. The analysis will be computed with SPSS version 28.0, and a predictor variable, P<0.05, will be regarded as statistically significant, with the utility of GA determined by plotting the area under the ROC curve and the confusion matrix.

Circulating glycated albumin levels and gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is characterized by glucose intolerance that is first diagnosed during pregnancy, making it the most common complication associated with this period. Early detection and targeted treatment of GDM can minimize foetal exposure to maternal hyperglycaemia and subsequently reduce the associated adverse pregnancy outcomes. Previous studies have inconsistently suggested that the level of glycated albumin (GA) might predict GDM.

AIM

To review and synthesize existing evidence to evaluate the relationship between GA levels and the development of GDM.

METHODS

We sought to compare GA levels between GDM and control groups in this meta-analysis by systematically searching the Web of Science, PubMed, Cochrane Library, and Embase databases for articles published up to June 2023. The analysis utilized the weighted mean difference (WMD) as the primary metric. The data were meticulously extracted, and the quality of the included studies was assessed. Additionally, we conducted a subgroup analysis based on study region and sample size. We assessed heterogeneity using I 2 statistics and evaluated publication bias through funnel plots. Additionally, trim-and-fill analysis was employed to detect and address any potential publication bias.

RESULTS

The meta-analysis included a total of 11 studies involving 5477 participants, comprising 1900 patients with GDM and 3577 control individuals. The synthesized results revealed a notable correlation between elevated GA levels and increased susceptibility to GDM. The calculated WMD was 0.42, with a 95% confidence interval (95%CI) ranging from 0.11 to 0.74, yielding a P value less than 0.001. Concerning specific GA levels, the mean GA level in the GDM group was 12.6, while for the control group, it was lower, at 11.6. This discrepancy underscores the potential of GA as a biomarker for assessing GDM risk. Moreover, we explored the levels of glycated haemoglobin (HbA1c) in both cohorts. The WMD for HbA1c was 0.19, with a 95%CI ranging from 0.15 to 0.22 and a P value less than 0.001. This observation suggested that both GA and HbA1c levels were elevated in individuals in the GDM group compared to those in the control group.

CONCLUSION

Our meta-analysis revealed a substantial correlation between elevated GA levels and increased GDM risk. Furthermore, our findings revealed elevated levels of HbA1c in GDM patients, emphasizing the significance of monitoring both GA and HbA1c levels for early GDM detection and effective management.

Exploring glycated sites in human serum albumin: impact of sample processing techniques on detection and analysis

Glycation and the subsequent formation of advanced glycation end products (AGEs) disrupt and impair the physiological functions of proteins. This study presents a comprehensive glycation site mapping of human serum albumin (HSA) utilizing liquid chromatography-tandem mass spectrometry (LC-MS/MS). Both in vitro glycation experiments and patient samples were investigated, exploring various enzymes, processing techniques, and their impacts on glycation site detection. A pilot study was conducted, analyzing sixteen serum samples, which spanned from healthy individuals to severe diabetic patients (with HbA1c values ranging from 5.7% to 18.1%). The aim was to comprehend the progression of glycation on various sites of HSA with increasing levels of glycation. Their glycated albumin levels (GA) spanned from 19.7% to 62.3%. Trypsin-mediated proteolytic digestion unveiled 12 glycation sites through direct in-solution digestion of whole serum. However, isolating albumin from serum enabled the identification of a higher number of glycation sites in each sample compared to direct serum digestion. Boronate affinity chromatography facilitated the segregation of less glycated albumin (LGA) from the more glycated albumin (MGA) fraction. Subsequent proteolytic digestion of both LGA and MGA samples revealed similar glycation sites. The MGA fraction exhibited a greater number of identified glycation sites, thereby elucidating which sites are particularly prone to glycation in highly glycated albumin samples. Changes in relative glycation levels were noted in the tryptic digests of albumin samples following the sample enrichment steps, as opposed to direct in-solution digestion of whole serum. Two enzymes, trypsin and Glu-C, were evaluated for efficacy in sequence coverage and glycation site analysis of HSA, with trypsin demonstrating superior efficiency over Glu-C.

Comparison of Glycated Hemoglobin (HbA1c) Values Estimated by High-Performance Liquid Chromatography and Spectrophotometry: A Pilot Study

Background Invasive blood sample collection followed by high-performance liquid chromatography (HPLC) based analysis is the gold standard for estimating glycated hemoglobin level or HbA1c currently. Spectrophotometry could be an alternative that holds the potential to be translated into a portable, non-invasive device for glycated hemoglobin level estimation. This study compares HbA1c values obtained from HPLC and spectrophotometry. Methods Venous blood samples were collected from both diabetic and non-diabetic participants in a cross-sectional study. The samples were subjected to both HPLC and spectrophotometry-based estimation of HbA1c%. The results obtained were compared, and the relationship between the two estimations were assessed. Results About 15 diabetic and non-diabetic individuals participated in the study and 28 samples were included in the final analysis. The Pearson's correlation coefficient was 0.65 (95% CI, 0.37-0.82), indicating that there was a strong positive association. This was further supported by the findings from linear regression analysis with a p-value of <0.001. Conclusions The positive correlation between the HPLC and spectrophotometric values supports the hypothesis that spectrophotometry could be an alternative to conventional HPLC for the measurement of HbA1c. This needs to be further validated through larger, well-powered studies.

Usefulness of glycated albumin level as a glycemic index complementing glycosylated hemoglobin in diabetic children and adolescents

PURPOSE

Glycated albumin (GA) is a glycemic marker reflecting the average serum glucose of the previous 2 weeks. This study aimed to evaluate the usefulness of GA as a glycemic index to complement glycosylated hemoglobin (HbA1c) in children and adolescents.

METHODS

Fifty-four children and adolescents with diabetes mellitus (DM) and 97 children and adolescents without DM (NDM) were enrolled. The correlation between mean blood glucose (MG) and GA compared to HbA1c was investigated in the DM group. The correlation between fasting glucose (FG) and GA compared to HbA1c was investigated in the NDM group. Factors affecting GA, HbA1c, and GA/HbA1c were analyzed.

RESULTS

In the DM group, positive correlations were observed between MG and GA (P=0.003), between MG and HbA1c (P=0.001), and between GA and HbA1c (P<0.001). The correlation coefficient between MG and GA did not differ from that between MG and HbA1c in the DM group (P=0.811). Among patients with DM, those whose standardized body mass index standard deviation score (BMI SDS) was ≥2 had a lower GA/HbA1c compared with those whose BMI SDS was <2 (P=0.001). In the NDM group, there were no significant correlations between FG and GA, between FG and HbA1c, or between GA and HbA1c. The NDM subjects whose BMI SDS was ≥2 had a lower GA/HbA1c than did the NDM subjects whose BMI SDS was <2 (P=0.003).

CONCLUSION

GA is comparable with HbA1c in reflecting glycemic control in children and adolescents with DM. GA is affected by obesity in children and adolescents with or without DM.

1-Amino-1-deoxy-d-fructose ("fructosamine") and its derivatives

Fructosamine has long been considered as a key intermediate of the Maillard reaction, which to a large extent is responsible for specific aroma, taste, and color formation in thermally processed or dehydrated foods. Since the 1980s, however, as a product of the Amadori rearrangement reaction between glucose and biologically significant amines such as proteins, fructosamine has experienced a boom in biomedical research, mainly due to its relevance to pathologies in diabetes and aging. In this chapter, we assess the scope of the knowledge on and applications of fructosamine-related molecules in chemistry, food, and health sciences, as reflected mostly in publications within the past decade. Methods of fructosamine synthesis and analysis, its chemical, and biological properties, and degradation reactions, together with fructosamine-modifying and -recognizing proteins are surveyed.

Development of a high-performance liquid chromatographic glycated albumin assay using finger-prick blood samples

BACKGROUND

Home blood glucose monitoring can be effective for the self-management of diabetic patients. Hemoglobin A1c (HbA1c) is a widely used marker that reflects the average blood glucose within 1-2 months but does not sensitively respond to behavioral changes. Self-monitoring of blood glucose, continuous glucose monitoring, and flush glucose monitoring are sensitive; however, the cost and invasiveness of these tests prevent their widespread use. We focused on glycated albumin (GA), which reflects the average blood glucose levels over 1-2 weeks, and established a GA measurement method for self-sampling, finger-prick blood, which may be submitted for testing through postal service to receive weekly results.

METHODS

A high-performance liquid chromatography assay was established to measure GA levels in finger-prick blood samples from 103 diabetic patients and the results were compared with venous blood measurements using an enzymatic method. Furthermore, conditions for sending blood samples by mail were evaluated. Under these conditions, samples from 27 healthy and 32 patient volunteers sent through postal service were compared with samples stored in the laboratory.

RESULTS

GA levels were measured in samples containing > 20 μg albumin, which resulted in a CV less than 0.3%. The correlation between the GA levels of finger-prick blood measured using HPLC and the GA levels of venous blood measured using the enzymatic method was R² = 0.988 with the slope ∼ 1.0, suggesting that the two were nearly equivalent. GA levels were stable for four days at 30 °C and two days at 37 °C. Mail-delivered samples exhibited a high correlation with samples that were not sent (R² > 0.99).

CONCLUSIONS

We established a method to measure GA levels in self-sampled, finger-prick blood sent through postal service in Japan. The method is applicable for weekly feedback of GA levels, which is potentially useful for motivating behavioral changes. In addition to markers such as HbA1c and blood glucose, GA can be used as a marker for assessing dietary and physical activities. This study highlighted the importance of GA monitoring by developing a suitable measurement method for weekly monitoring of GA levels.

Aptamer-Based Glycated Albumin Sensor for Capacitive Spectroscopy

Glycated albumin (GA) is a candidate for glycemic indicator to control prediabetes, the half-life of which is about 2 weeks, which is neither too long nor too short, considering that there is no longer any need for daily fingerstick sampling but glucose levels can be controlled in a relatively short term. Its usefulness as a glycemic indicator must be widely recognized by developing a simple and miniaturized GA sensor for point-of-care testing (POCT) devices. In this study, we propose an aptamer-based capacitive electrode for electrochemical capacitance spectroscopy (ECS) to specifically detect GA in an enzyme-/antibody-free manner. As a component of the bioelectrical interface between the sample solution and the electrode, a densely packed capacitive polyaryl film coated on a gold electrode contributes to the detection of GA by the ECS method. In addition, the GA aptamer tethered onto the polyaryl-film-coated gold electrode is useful for not only specifically capturing GA but also inducing changes in the concentration of cations released from the cation/GA aptamer complexes by GA/GA aptamer binding. Also, hydrophilic poly(ethylene glycol) (PEG) coated on the polyaryl film electrode in parallel with the GA aptamer prevents interfering proteins such as human serum albumin (HSA) and immunoglobulin G (IgG) from nonspecifically absorbing on the polyaryl film electrode. Such a GA aptamer-based capacitive electrode produces significant signals of GA against HSA and IgG with the change in GA concentration (0.1, 1, and 10 mg/mL) detected by the ECS method. This indicates that the ECS method contributes to the evaluation of the GA level, which is based on the rate of glycation of albumin. Thus, a platform based on ECS measurement using the aptamer-based capacitive electrode is useful for protein analysis in an enzyme-/antibody-free manner.

Predicting the response to SGLT-2 inhibitors as add-on therapy to multiple day injection insulin with glycated albumin: a pilot study

BACKGROUND

Achieving optimal glycemic targets is the main therapeutic goal in patients with type 2 diabetes (T2D) mellitus. HbA1c is the reference biomarker for monitoring glycemic control; however, in specific conditions affecting erythrocyte turnover or in patients on multiple daily injection (MDI) insulin regimens, the determination of glycated albumin (GA) may be preferable. Sodium-glucose cotransporter-2 (SGLT-2) inhibitors represent a novel class of antidiabetic drugs that lower plasma glucose concentrations quickly, with insulin-independent mechanisms. Herein, we explored the role of GA in predicting the short-term response to SGLT-2 inhibitors as add-on to MDI insulin.

METHODS

Sixteen patients with long-standing, poorly controlled T2D on MDI insulin starting an SGLT-2 inhibitor were subjected to plasma GA and HbA1c measurements at 30 days intervals for up to 3 months in order to examine the temporal changes of these glycemic biomarkers.

RESULTS

At the end of the study, grossly coincident with the life span of erythrocytes, a significant decrease in median HbA1c was observed, (from 8.7 [range: 8.2-9.3%] at baseline to 7.2 [range: 7.0-7.9%]), with the advantage of less insulin dose requirements. However, significant, and incremental reductions in median GA determinations could be already evident after 30 days (-3.5 [range: -7.5, -2.5%]) and 60 days (-6.4 [range: -10.5, -4.7%]) from the start of SGLT-2 inhibitor treatment and persisted for up to 3 months (-8.6 [range: -12.1, 6.1%]). The decrements of HbA1c observed at the 3-month visit were highly correlated with the concurrent absolute reductions of plasma GA (ρ=0.550, P=0.027), whereas a borderline significance could be demonstrated with reference to reductions in plasma GA at 30 and 60 days.

CONCLUSIONS

Although limited by the small number of participants, these preliminary findings suggest that GA, rather than HbA1c, could represent a useful and reliable biomarker in T2D to monitor the early glucose-lowering effects of antidiabetic drugs with rapid onset of action, such as SGLT-2 inhibitors and MDI insulin.

In Vitro and In Vivo Antiglycation Effects of Connarus ruber Extract

Accumulation of advanced glycation end products (AGEs) of the Maillard reaction has been implicated in the pathogenesis of diabetes and its complications. Connarus ruber has been used as a folk remedy for several diseases, including diabetes; however, its underlying mechanism has not yet been investigated. This study investigated the effects of C. ruber extract against glycation on collagen-linked AGEs in vitro and streptozotocin-induced diabetic rats (STZ-DM rats) in vivo. The antiglycation activities of C. ruber extract and aminoguanidine (AG) were examined using a collagen glycation assay kit. Nonfluorescent AGE, N^ε-carboxymethyl lysine (CML), N^ω-carboxymethyl arginine, and N^ε-carboxyethyl lysine levels were measured via electrospray ionization-liquid chromatography-tandem mass spectrometry. The effect of the extract on the cytotoxicity of methylglyoxal (MG), a precursor of AGEs, was examined in HL60 cells. STZ-DM rats were treated with the extract for 4 wk, and the effect was assessed using biochemical markers in the serum and CML-positive cells in renal tissues. C. ruber extract dose-dependently inhibited the glycation of collagen and formation of nonfluorescent AGEs, which was comparable to AG, and it significantly attenuated MG-induced cytotoxicity in HL60 cells. Furthermore, the glycated albumin levels in STZ-DM rats decreased, the increase in serum lipid levels was reversed, and immunohistochemistry demonstrated that CML deposition in the glomerulus of STZ-DM rats significantly decreased. Although further studies are needed, C. ruber could be a potential therapeutic for preventing and progressing many pathological conditions, including diabetes.

Biomarkers in Diabetes Mellitus

Diabetes mellitus (DM) is a chronic metabolic disease characterized by hyperglycemia that occurs as a result of impaired insulin secretion and/or insulin effect, or both of these factors. The fact that the disease has both individual and social dimensions makes it important to detect as early as possible and make the necessary lifestyle changes. For this purpose, it becomes necessary to develop fast, effortless, cheap, and reliable methods for diagnosis. We discussed which biochemical markers should enter routine use according to their sensitivity and specificity among the biochemical markers that have been used and are still being studied. In this chapter, we explored some methods that may be used as biomarkers and discussed advantages and pitfalls for each.

Analytical Challenges in Diabetes Management: Towards Glycated Albumin Point-of-Care Detection

Diabetes mellitus is a worldwide-spread chronic metabolic disease that occurs when the pancreas fails to produce enough insulin levels or when the body fails to effectively use the secreted pancreatic insulin, eventually resulting in hyperglycemia. Systematic glycemic control is the only procedure at our disposal to prevent diabetes long-term complications such as cardiovascular disorders, kidney diseases, nephropathy, neuropathy, and retinopathy. Glycated albumin (GA) has recently gained more and more attention as a control biomarker thanks to its shorter lifespan and wider reliability compared to glycated hemoglobin (HbA1c), currently the “gold standard” for diabetes screening and monitoring in clinics. Various techniques such as ion exchange, liquid or affinity-based chromatography and immunoassay can be employed to accurately measure GA levels in serum samples; nevertheless, due to the cost of the lab equipment and complexity of the procedures, these methods are not commonly available at clinical sites and are not suitable to home monitoring. The present review describes the most up-to-date advances in the field of glycemic control biomarkers, exploring in particular the GA with a special focus on the recent experimental analysis techniques, using enzymatic and affinity methods. Finally, analysis steps and fundamental reading technologies are integrated into a processing pipeline, paving the way for future point-of-care testing (POCT). In this view, we highlight how this setup might be employed outside a laboratory environment to reduce the time from measurement to clinical decision, and to provide diabetic patients with a brand-new set of tools for glycemic self-monitoring.

Recent Developments in Biomarkers for Diagnosis and Screening of Type 2 Diabetes Mellitus

PURPOSE OF REVIEW

Diabetes mellitus is a complex, chronic illness characterized by elevated blood glucose levels that occurs when there is cellular resistance to insulin action, pancreatic β-cells do not produce sufficient insulin, or both. Diabetes prevalence has greatly increased in recent decades; consequently, it is considered one of the fastest-growing public health emergencies globally. Poor blood glucose control can result in long-term micro- and macrovascular complications such as nephropathy, retinopathy, neuropathy, and cardiovascular disease. Individuals with diabetes require continuous medical care, including pharmacological intervention as well as lifestyle and dietary changes.

RECENT FINDINGS

The most common form of diabetes mellitus, type 2 diabetes (T2DM), represents approximately 90% of all cases worldwide. T2DM occurs more often in middle-aged and elderly adults, and its cause is multifactorial. However, its incidence has increased in children and young adults due to obesity, sedentary lifestyle, and inadequate nutrition. This high incidence is also accompanied by an estimated underdiagnosis prevalence of more than 50% worldwide. Implementing successful and cost-effective strategies for systematic screening of diabetes mellitus is imperative to ensure early detection, lowering patients' risk of developing life-threatening disease complications. Therefore, identifying new biomarkers and assay methods for diabetes mellitus to develop robust, non-invasive, painless, highly-sensitive, and precise screening techniques is essential. This review focuses on the recent development of new clinically validated and novel biomarkers as well as the methods for their determination that represent cost-effective alternatives for screening and early diagnosis of T2DM.

Serum glycated albumin as good biomarker for predicting type 2 diabetes: A retrospective cohort study of China National Diabetes and Metabolic Disorders Survey

AIMS

Glycated albumin (GA) is a biomarker for short-term (2-3 weeks) glycaemic control. However, the predictive utility of GA for diabetes and prediabetes is largely uncharacterised. We aimed to investigate the relationships of baseline serum GA levels with incident diabetes and prediabetes.

METHODS

This was a longitudinal cohort study involving 516 subjects without diabetes or prediabetes at baseline. Blood glucose levels were observed during follow-up. Hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated using COX proportional hazard models. Receiver operating characteristic curves and areas under the curves (AUCs) were used to evaluate the discriminating abilities of glycaemic biomarkers and prediction models.

RESULTS

During a 9-year follow-up, 51 individuals (9.88%) developed diabetes and 92 (17.83%) prediabetes. Unadjusted HRs (95% CI) for both diabetes and prediabetes increased proportionally with increasing GA levels in a dose-response manner. Multivariable-adjusted HRs (95% CI) for diabetes were significantly elevated from 1.0 (reference) to 5.58 (1.86-16.74). However, the trend was no longer significant for prediabetes after multivariable adjustment. AUCs for GA, fasting blood glucose (FBG) and 2-h postprandial blood glucose (2h-PBG) for predicting diabetes were 0.698, 0.655 and 0.725, respectively. The AUCs for GA had no significant differences compared with those for FBG (p = 0.376) and 2h-PBG (p = 0.552). Replacing FBG or 2h-PBG or both with GA in diabetes prediction models made no significant changes to the AUCs of the models.

CONCLUSIONS

GA is of good prognostic utility in predicting diabetes. However, GA may not be a useful biomarker for predicting prediabetes.

Current Challenges and Future Trends of Enzymatic Paper-Based Point-of-Care Testing for Diabetes Mellitus Type 2

A point-of-care (POC) can be defined as an in vitro diagnostic test that can provide results within minutes. It has gained enormous attention as a promising tool for biomarkers detection and diagnosis, as well as for screening of chronic noncommunicable diseases such as diabetes mellitus. Diabetes mellitus type 2 is one of the metabolic disorders that has grown exponentially in recent years, becoming one of the greatest challenges to health systems. Early detection and accurate diagnosis of this disorder are essential to provide adequate treatments. However, efforts to reduce incidence should remain not only in these stages but in developing continuous monitoring strategies. Diabetes-monitoring tools must be accessible and affordable; thus, POC platforms are attractive, especially paper-based ones. Paper-based POCs are simple and portable, can use different matrixes, do not require highly trained staff, and are less expensive than other platforms. These advantages enhance the viability of its application in low-income countries and hard-to-reach zones. This review aims to present a critical summary of the main components required to create a sensitive and affordable enzymatic paper-based POC, as well as an oriented analysis to highlight the main limitations and challenges of current POC devices for diabetes type 2 monitoring and future research opportunities in the field.

The binding of apo and glucose-bound human serum albumins to a free graphene sheet in aqueous environment: Simulation studies

Human serum albumin (HSA) is a blood protein serving as a carrier for a wide range of drugs and nutrients. A level of glycated HSA (GHSA) is used as a diabetes biomarker. A graphene-based aptasensor is one of potential techniques to detect GHSA. Not only the interactions of albumin and aptamer, but the albumin-graphene (GRA) binding mechanism are also crucial for developing a diabetes aptasensor. In this work, Molecular Dynamics simulations (MD) were employed to explore the binding of GRA to both GHSA and HSA. The GRA binding from the back and front sides of an albumin are fast and spontaneous. The multiple GRA binding sites are identified. GRA causes more denaturation of helical characteristics in GHSA (∼12% reduction of helical structure). Both back and front GRA adhesions generate comparable degrees of helical unfolding. Importantly, the presence of bound GRA induces the release of glucose from drug sites implying the loss of ligand-binding affinity. This loss of drug site activity is independent on the GRA binding positions because all bound positions lead to the exit of sugars. The GRA binding deconstructs not only secondary structure, but also albumin function. Apparently, GRA is a non-biocompatible material for albumin. To construct a potential graphene-based aptasensor to detect GHSA, it is necessary to be certain that no free GRA surface is available because a bare GRA can bind and denature both HSA and GHSA which can cause misleading data.

Diabetes mellitus in chronic kidney disease: Biomarkers beyond HbA1c to estimate glycemic control and diabetes-dependent morbidity and mortality

Diabetes mellitus (DM) is the leading cause of chronic kidney disease (CKD). Optimal glycemic control contributes to improved outcomes in patients with DM, particularly for microvascular damage, but blood glucose levels are too variable to provide an accurate assessment and instead markers averaging long-term glycemic load are used. The most established glycemic biomarker of long-term glycemic control is HbA1c. Nevertheless, HbA1c has pitfalls that limit its accuracy to estimate glycemic control, including the presence of altered red blood cell survival, hemoglobin glycation and suboptimal performance of HbA1c assays. Alternative methods to evaluate glycemic control in patients with DM include glycated albumin, fructosamine, 1-5 anhydroglucitol, continuous glucose measurement, self-monitoring of blood glucose and random blood glucose concentration measurements. Accordingly, our aim was to review the advantages and pitfalls of these methods in the context of CKD.

Individualized Correction of the Interference of Hemolysis on Glycated Albumin Determined by the Ketamine Oxidase Method

OBJECTIVE

To investigate the effect of hemolysis on glycated albumin (GA) levels, as determined by the ketamine oxidase method.

METHODS

GA levels and the hemolysis index were determined in nonhemolyzed serum and hemolyzed serum from corresponding patients. We developed an equation to correct the interference of hemolysis on GA, using multiple regression analysis.

RESULTS

The degree of hemolysis was negatively correlated with GA levels (R2 = 0.9500). A correction equation for GA (corrected GA = 2.703 × OD of hemolysis + 1.044 × measured GA -0.906) can revert GA concentrations of hemolyzed specimens to values that were not significantly different from the GA concentration of corresponding nonhemolyzed specimens. The bias of GA concentrations before and after correction was statistically significantly different (P <.01).

CONCLUSIONS

Our results indicate that the level of GA measured through the ketamine oxidase method is negatively affected by hemolysis. The individualized correction of GA results provides increased accuracy in hemolyzed specimens.

Results of a Study Comparing Glycated Albumin to Other Glycemic Indices

CONTEXT

Intermediate-term glycemic control metrics fulfill a need for measures beyond hemoglobin A1C.

OBJECTIVE

Compare glycated albumin (GA), a 14-day blood glucose measure, with other glycemic indices.

DESIGN

24-week prospective study of assay performance.

SETTING

8 US clinics.

PARTICIPANTS

Subjects with type 1 (n = 73) and type 2 diabetes (n = 77) undergoing changes to improve glycemic control (n = 98) or with stable diabetes therapy (n = 52).

INTERVENTIONS

GA, fructosamine, and A1C measured at prespecified intervals. Mean blood glucose (MBG) calculated using weekly self-monitored blood glucose profiles.

MAIN OUTCOME MEASURES

Primary: Pearson correlation between GA and fructosamine. Secondary: magnitude (Spearman correlation) and direction (Kendall correlation) of change of glycemic indices in the first 3 months after a change in diabetes management.

RESULTS

GA was more concordant (60.8%) with changes in MBG than fructosamine (55.5%) or A1C (45.5%). Across all subjects and visits, the GA Pearson correlation with fructosamine was 0.920. Pearson correlations with A1C were 0.655 for GA and 0.515 for fructosamine (P < .001) and with MBG were 0.590 and 0.454, respectively (P < .001). At the individual subject level, Pearson correlations with both A1C and MBG were higher for GA than for fructosamine in 56% of subjects; only 4% of subjects had higher fructosamine correlations with A1C and MBG. GA had a higher Pearson correlation with A1C and MBG in 82% and 70% of subjects, respectively.

CONCLUSIONS

Compared with fructosamine, GA correlates significantly better with both short-term MBG and long-term A1C and may be more useful than fructosamine in clinical situations requiring monitoring of intermediate-term glycemic control (NCT02489773).

Modification of reduced graphene/Au-aptamer to develop an electrochemical based aptasensor for measurement of glycated albumin

Herein, an electrochemical label-free biosensor designed for the detection of glycated albumin (GA) using reduced graphene oxide/Au nanoparticles (RGO/AuNPs) modified by anti-GA aptamer. For fast and simple modification of the electrode, the aptamer chain was thiolated. Transition electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) techniques were used to the characterization of synthesized materials. Structural analysis of nanomaterials shows that graphene sheets were synthesized very fine by average thickness of 2.5 nm and Au nanoparticles distributed on the surface of graphene sheets uniformly. Cyclic voltammetry (CV) square wave voltammetry (SWV) and impedance spectroscopy (EIS) were used to electrochemical study of the decorated electrode. Electrochemical studies described the potential of fabricated rGO/AuNPs-aptamer electrode to selectively determine GA properly in buffer solution at the range of 2-10 μg mL^-1 by the detection limit of 0.07 μg. mL^-1 for GA.

The association between glycated albumin, glycohemoglobin, and glycated albumin to glycohemoglobin ratio in diabetic retinopathy of prediabetes

Prediabetes increased risk of diabetes and diabetes-related macrovascular and microvascular complication. Glycohemoglobin (HbA_1c ) is clinically used as the gold standard for glycemic control of diabetes. Glycated albumin (GA) is an early Amadori-type glycation protein between glucose and serum albumin, which changes in a shorter period of time than HbA_1c and is superior to HbA_1c in reflecting fluctuations in blood glucose. In this study, we aim to assess the predictive value of GA and glycohemoglobin (HbA1c) on a progression of diabetic retinopathy (DR) in prediabetic patients in Taiwan. This study was conducted at the outpatient department of a regional hospital in Southern Taiwan, and recruited 291 patients with prediabetes from January 2016 to February 2017. Blood and urine samples were obtained from all patients after fasting for 12 hours within 1 month of enrollment. The mean age is 62.5 ± 13.0 years and there are 161 males and 130 females. A total of 24.1% of patients have DR. The average value of GA and HbA1c are 14.6% ± 2.8% and 6.0% ± 0.4%, respectively. Old age, male, high systolic blood pressure, high HbA_1C , and low total cholesterol are significantly associated with DR in patients with pre-DM. Therefore, in the prediabetic populations, high HbA_1C, but not GA nor GA/HbA_1C ratio, is significantly associated with DR.

Association between glycated albumin, fructosamine, and HbA1c with neonatal outcomes in a prospective cohort of women with gestational diabetes mellitus

OBJECTIVE

To investigate whether glycated albumin, fructosamine, and hemoglobin A1c (HbA1c) are associated with neonatal complications in newborns of pregnant women with gestational diabetes mellitus (GDM).

METHODS

Between November 2016 and September 2017, women with a singleton pregnancy and GDM were enrolled in a prospective study in an obstetric Portuguese referral center. Glycemic markers were compared between mothers of newborns with and without complications. Multivariable logistic regression models and corresponding areas under the receiver operating characteristic curve (AUC) were used.

RESULTS

A total of 85 women participated in the study. Raised levels of glycated albumin and fructosamine were associated with at least one neonatal complication (OR- [odds ratio] estimate: 1.33, P=0.015; OR: 1.24, P=0.027, respectively) and with respiratory disorders at birth (OR 1.41, P=0.004; OR 1.26, P=0.014, respectively). HbA1c was not associated with these outcomes. All biomarkers were associated with large-for-gestational age (LGA) status (OR 1.61, P<0.001; OR 1.45, P<0.001; OR 3.62, P=0.032 for glycated albumin, fructosamine, and HbA1c, respectively). All had similar AUC for at least one neonatal complication (0.82; 0.81; 0.79, respectively). For newborn respiratory disorders, AUCs were 0.83, 0.81, and 0.76, respectively, and for LGA status were 0.81, 0.79, and 0.71, respectively.

CONCLUSION

Raised values of glycated albumin and fructosamine were associated with particular perinatal complications in newborns of mothers with GDM, better discriminating mothers of newborns with and without complications than HbA1c.

Reference interval determination for glycated albumin in defined subgroups of a South African population

Background

Glycated proteins, such as glycated haemoglobin (HbA1c) and glycated albumin (GA%), are increasingly being used for glycaemic control assessment and the diagnosis of diabetes mellitus. GA% is an intermediate marker of glycaemic control that is not influenced by factors that affect HbA1c concentrations. The aim of this study was to determine reference intervals and assess confounding factors for glycated albumin in a well-characterized healthy population in South Africa.

Methods

We measured glycated albumin using an enzymatic method on stored serum samples of healthy individuals recruited in Cape Town, South Africa. Reference intervals (overall and specific for age, sex and ethnicity) were determined using non-parametric methods and confounding factors were assessed using multiple regression analysis.

Results

The reference interval (2.5th to 97.5th percentile) for glycated albumin of 663 healthy individuals (mean age, 34 years, 38.6% males) ranged from 10.7 to 15.2%. Sex, body mass index categories and ethnicity were significantly associated with the glycated albumin and were considered of practical importance because their standardized regression coefficients (Beta) were greater than a cut-off of 0.15, implying a stronger effect on glycated albumin ( P < 0.001). The glycated albumin reference intervals for subjects with body mass index <25 kg/m2 was 11.2–15.3%, for body mass index 25–30 kg/m2 it was 10.5–14.9% and 10.0–14.6% for body mass index >30 kg/m2 ( P = 0.0001).

Conclusions

The overall reference interval showed good correlation with reference intervals determined in other studies. However, sex, ethnicity and body mass index were statistically significant confounding factors that may influence the overall reference interval. Therefore, overall glycated albumin reference intervals should be used cautiously.

Association between glycated haemoglobin, glycated albumin and fructosamine with neonatal birthweight and large-for-date status infants in gestational diabetes mellitus: a prospective cohort study

This study aims to investigate associations between glycated haemoglobin (HbA1c), glycated albumin (GA) and fructosamine with neonatal birthweight in gestational diabetes mellitus (GDM). The prospective cohort consisted of 82 women with GDM and their newborns, enrolled between November 2016 and September 2017. Considering neonatal birthweight and birthweights ≥90th percentile for gestational age as outcomes, linear and logistic regression models were used, respectively. Fructosamine (R²=0.62) and GA (R²=0.61) performed very similarly between them and best than HbA1c (R²=0.58). The added value of GA or fructosamine to HbA1c resulted in increase in models' performances. GA attained the best discriminative ability regarding large-for-date status babies (AUC = 0.80, OR-estimate 1.58, p=.001) followed by fructosamine (AUC = 0.78, OR-estimate 1.42, p=.001) and HbA1c (AUC = 0.69, OR-estimate 3.09, p=.070). GA and fructosamine, besides from providing additional information to HbA1c, when used separately perform better than the traditional biomarker in predicting neonatal birthweight and large-for-date babies in pregnant women with GDM. Impact statement What is already known on this subject? HbA1c is the standard glycaemic indicator used in GDM. Its association with birthweight and large-for-date status has been previously reported. However, it has become increasingly questionable whether it is a suitable glycaemic marker in pregnancy. There is a growing interest in other non-traditional shorter-term glycaemic indicators, such as GA and fructosamine. Nevertheless, few studies exist and almost all are retrospective and with ethnically homogeneous study populations composed by pregnant women not only with GDM but also type 1 and type 2 diabetes mellitus. What do the results of this study add? Our prospective multi-ethnic cohort composed solely on pregnant women with GDM and their infants show that even though all of the aforementioned biomarkers are associated with birthweight and large-for-date status in GDM when used separately, GA and fructosamine seem to perform better than HbA1c. When used with HbA1c, they improve the predicting performance of the traditional marker. What are the implications of these findings for future clinical practice and/or further research? These findings suggest that GA and fructosamine can provide important additional or substitute information to HbA1c in GDM, namely in predicting birthweight and large-for-date status babies. Larger studies are needed to confirm if this non-traditional biomarkers can change clinical practice.

Influence of Type 2 Diabetes Mellitus and Preoperative Hemoglobin A1c Levels on Outcomes of Liver Transplantation

Liver transplant centers often establish hemoglobin A1c (HbA1C) criteria for candidates with type 2 diabetes mellitus (T2DM) based on data from other surgical specialties showing worse outcomes in patients with poor glycemic control. However, because of the reduced reliability of HbA1C in cirrhosis, it is unclear whether pretransplant HbA1C values are predictive of postoperative complications in liver recipients. We retrospectively examined the association between preoperative HbA1C and postoperative outcomes in 173 consecutive patients who underwent liver transplantation at the University of Cincinnati Medical Center between August 2012 and March 2015. Demographic correlates of pretransplant HbA1C included age, T2DM, native Model for End‐Stage Liver Disease, hemoglobin, serum albumin, and nonalcoholic steatohepatitis as the indication for transplantation. No association was identified between pretransplant HbA1C and most outcome measures, including survival, length of stay, reoperation or readmission rates, rejection, bacteremia, and viremia. Significant correlates of HbA1C in liver recipients with diabetes were posttransplant insulin requirement and anastomotic biliary stricture formation. On multivariate analysis, HbA1C was the sole determinant of biliary strictures, with patients in the highest quartile (HbA1C >7.3%) exhibiting a 4‐fold increased risk. Correlation of HbA1C with morning blood glucose levels was much tighter after versus before transplantation. Conclusion: Preoperative HbA1C is predictive of anastomotic biliary stricture formation and the need for insulin following liver transplantation.

Quantitative analysis of glycated albumin in serum based on ATR-FTIR spectrum combined with SiPLS and SVM

A rapid quantitative analysis model for determining the glycated albumin (GA) content based on Attenuated total reflectance (ATR)-Fourier transform infrared spectroscopy (FTIR) combining with linear SiPLS and nonlinear SVM has been developed. Firstly, the real GA content in human serum was determined by GA enzymatic method, meanwhile, the ATR-FTIR spectra of serum samples from the population of health examination were obtained. The spectral data of the whole spectra mid-infrared region (4000-600 cm^-1) and GA's characteristic region (1800-800 cm^-1) were used as the research object of quantitative analysis. Secondly, several preprocessing steps including first derivative, second derivative, variable standardization and spectral normalization, were performed. Lastly, quantitative analysis regression models were established by using SiPLS and SVM respectively. The SiPLS modeling results are as follows: root mean square error of cross validation (RMSECV_T) = 0.523 g/L, calibration coefficient (R_C) = 0.937, Root Mean Square Error of Prediction (RMSEP_T) = 0.787 g/L, and prediction coefficient (R_P) = 0.938. The SVM modeling results are as follows: RMSECV_T = 0.0048 g/L, R_C = 0.998, RMSEP_T = 0.442 g/L, and R_p = 0.916. The results indicated that the model performance was improved significantly after preprocessing and optimization of characteristic regions. While modeling performance of nonlinear SVM was considerably better than that of linear SiPLS. Hence, the quantitative analysis model for GA in human serum based on ATR-FTIR combined with SiPLS and SVM is effective. And it does not need sample preprocessing while being characterized by simple operations and high time efficiency, providing a rapid and accurate method for GA content determination.

Glycated albumin and the risk of chronic kidney disease in subjects with Type 2 Diabetes: A study in North Indian Population

AIM

Glycated albumin (GA) suggested being alternative glycemic marker than haemoglobin A1C (HbA1c) in patients with chronic kidney diseases (CKD). We investigated the association between GA and the progression of diabetic nephropathy (DN) in T2DM subjects.

METHODS

We recruited T2DM subjects with different stages of CKD who had regularly measured serum creatinine and estimated glomerular filtration rates (eGFR) according to Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines, HbA1c consecutively every 3 months along with GA levels and other anthropometric and demographic measurements. We grouped age and sex matched subjects into the CKD progression, Group I healthy subjects (n = 100, M: F;50:50). Group II T2DM subjects with eGFR ≥90 mL/min (n = 167, M:F; 76:91). Group III of T2DM patients with eGFR 60-89 mL/min (n = 91, M:F; 44:47). Group IV T2DM subjects with eGFR 30-59 mL/min (n = 68, M:F;31:37). Group V T2DM with eGFR ≤ 29 mL/min (n = 21, M:F; 13:8).

RESULTS

Pearson's correlation analysis between glycated albumin and biochemical parameters were established in all subjects. GA/HbA1c ratio increases with poor glycemic control except for nephrosis state.

CONCLUSION

Mean GA levels were more closely associated with DN progression than mean HbA1c in subjects with T2DM and can be implemented as an alternative diagnostic marker in nephropathy.

Aptasensor based optical detection of glycated albumin for diabetes mellitus diagnosis

Glycated albumin (GA) has been reported as an important biomarker for diabetes mellitus. This study investigates an optical sensor comprised of deoxyribonucleic acid (DNA) aptamer, semiconductor quantum dot and gold (Au) nanoparticle for the detection of GA. The system functions as a 'turn on' sensor because an increase in photoluminescence intensity is observed upon the addition of GA to the sensor. This is possibly because of the structure of the DNA aptamer, which folds to form a large hairpin loop before the addition of the analyte and is assumed to open up after the addition of target to the sensor in order to bind to GA. This pushes the quantum dot and the Au nanoparticle away causing an increase in photoluminescence. A linear increase in photoluminescence intensity and quenching efficiency of the sensor is observed as the GA concentration is varied between 0-14 500 nM. Time based photoluminescence studies with the sensor show the decrease in binding rate of the aptamer to the target within a specific time period. The sensor was found to have a higher selectivity towards GA than other control proteins. Further investigation of this simple sensor with greater number of clinical samples can open up avenues for an efficient diagnosis and monitoring of diabetes mellitus when used in conjunction with the traditional method of glucose level monitoring.

Do glycoalbumin levels preferentially reflect changes in postprandial glucose excursions?

AIMS

To evaluate whether plasma glycated albumin, which provides an integrated measure of plasma glucose levels over the preceding 2-4 weeks, better reflects changes in postprandial glucose excursions than HbA_1c .

METHODS

People with suboptimum glycaemic control on dual oral therapy were enrolled in the Treating-to-Target-in-Type 2 diabetes (4-T) trial, in which participants were randomized to the addition of once-daily basal insulin, twice-daily biphasic insulin or thrice-daily prandial insulin. Glycated albumin levels were assayed enzymatically from baseline and 1-year fasting plasma samples. We evaluated robust correlations of glycated albumin and HbA_1c both with fasting and postprandial glucose levels at these two time points, and with insulin-induced changes in the postprandial excursion.

RESULTS

Requisite data were available for 625 of the participants in the 4-T trial. Their mean (±sd) age was 62 ± 10 years and body weight was 85.8 ± 15.9 kg, and their median (interquartile range) diabetes duration was 9 (6, 13) years. Partial correlations at baseline and 1 year between postprandial glucose excursions and glycated albumin/HbA_1c , after adjusting for fasting glucose, were 0.27/0.15 and 0.22/0.18, respectively. Glycated albumin, compared with HbA_1c , explained 66% more of the variation in postprandial glucose excursions at baseline. At 1 year, postprandial glucose excursions on basal, biphasic and prandial and insulin therapy were reduced by 0.43, 0.78 and 1.88 mmol/l, respectively. These reductions were associated with changes in both glycated albumin and HbA_1c (P < 0.01), with a stronger association for glycated albumin.

CONCLUSION

Changes in glycated albumin and HbA_1c reflect changes in postprandial glucose excursions to a similar extent.

Abundance matters: role of albumin in diabetes, a proteomics perspective

INTRODUCTION

Human serum albumin (HSA) is a multifaceted protein with vital physiological functions. It is the most abundant plasma protein with inherent capability to bind to diverse ligands, and thus susceptible to various post-translational modifications (PTMs) which alter its structure and functions. One such PTM is glycation, a non-enzymatic reaction between reducing sugar and protein leading to formation of heterogeneous advanced glycation end products (AGEs). Glycated albumin (GA) concentration increases significantly in diabetes and is implicated in development of secondary complications. Areas covered: In this review, we discuss in depth, formation of GA and its consequences, approaches used for characterization and quantification of GA, milestones in GA proteomics, clinical relevance of GA as a biomarker, significance of maintaining abundant levels of albumin and future perspectives. Expert commentary: Elevated GA levels are associated with development of insulin resistance as well as secondary complications, in healthy and diabetic individuals respectively. Mass spectrometry (MS) based approaches aid in precise characterization and quantification of GA including early and advanced glycated peptides, which can be useful in prediction of the disease status. Thus GA has evolved to be one of the best candidates in the pursuit of diagnostic markers for prediction of prediabetes and diabetic complications.

Definition of the upper reference limit of glycated albumin in blood donors from Italy

Background:

Glycated Albumin (GA) has been proposed as a short-term indicator of glycemic homeostasis. The aim of this study is to describe the distribution of GA in a large sample of blood donors from Italy to evaluate whether demographic features, namely age and sex, could influence GA levels and define specific reference limits.

Methods:

The study included 1334 Italian blood donors. GA was measured using an enzymatic method (quantILab Glycated Albumin, IL Werfen, Germany). The upper reference limit (URL) was calculated using the non-parametric percentile method.

Results:

A modest, although significant, increase of GA was observed in relation to age (p<0.001), especially in males, where the differences were more pronounced (p<0.001 in males, p=0.003 in females). Slight differences were documented based on sex (12% [11.3–12.8] in males; 12.2% [11.4–13.1] in females; p=0.01). After excluding individuals with fasting plasma glucose ≥7 mmol/L, the calculated GA URL was 14.5% (95% CI: 14.3–14.7). Subjects with GA>14.5% presented a mean age of 48.4±12.2 years, 66.7% were males and the mean glucose was 6.88±2.5 mmol/L.

Conclusions:

GA in Caucasians shows a similar increasing trend at older ages documented in other ethnicities. The definition of the URL in this population could be useful for both clinical studies, which will clarify the role of GA for diagnosing and monitoring diabetes, and will encourage the introduction of GA in clinical practice.

Glycated albumin: a potential biomarker in diabetes

Diabetes mellitus (DM) is a chronic and metabolic disease that presents a high global incidence. Glycated hemoglobin (A1C) is the reference test for long-term glucose monitoring, and it exhibits an association with diabetic chronic complications. However, A1C is not recommended in clinical situations which may interfere with the metabolism of hemoglobin, such as in hemolytic, secondary or iron deficiency anemia, hemoglobinopathies, pregnancy, and uremia. The glycated albumin (GA) is a test that reflects short-term glycemia and is not influenced by situations that falsely alter A1C levels. GA is the higher glycated portion of fructosamine. It is measured by a standardized enzymatic methodology, easy and fast to perform. These laboratory characteristics have ensured the highlight of GA in studies from the last decade, as a marker of monitoring and screening for DM, as well as a predictor of long-term outcomes of the disease. The aim of this review was to discuss the physiological and biochemistry characteristics of the GA, as well as its clinical utility in DM.

Glycated albumin is stable in plasma when exposed to common laboratory conditions and comparable when drawn from venous or capillary sites

BACKGROUND

Circulating glycated albumin is a marker of blood glucose reflecting the previous 2 weeks. However, the effects of storage conditions and draw site on glycated albumin values are not fully understood.

METHODS

Fifteen plasma samples from people with type 2 diabetes were assessed during repeated freeze-thaw rounds for 10 cycles. A further 15 samples were stored at 4°C and assessed over 3 days. Another 40 samples drawn concurrently from capillary and venous sites had their glycated albumin content compared.

RESULTS

Glycated albumin concentration did not alter over 10 freeze-thaw cycles (P=.856), or after 72 hours at 4°C (P=.962). Capillary and venous samples did not differ in their percentage of glycated albumin (P=.379), although lower concentrations of albumin and glycated albumin (g/dL) were observed in the capillary sample (P<.001).

CONCLUSION

Glycated albumin in plasma appears relatively stable when exposed to common laboratory conditions, reducing a potential confounder to its use as a marker of blood glucose control. The glycated albumin (%) in samples from capillary and venous sites was comparable, suggesting the potential of rapid or portable assessment devices that require a finger prick.

Evaluation of glycated albumin (GA) and GA/HbA1c ratio for diagnosis of diabetes and glycemic control: A comprehensive review

Diabetes Mellitus (DM) is a group of metabolic diseases characterized by chronic high blood glucose concentrations (hyperglycemia). When it is left untreated or improperly managed, it can lead to acute complications including diabetic ketoacidosis and non-ketotic hyperosmolar coma. In addition, possible long-term complications include impotence, nerve damage, stroke, chronic kidney failure, cardiovascular disease, foot ulcers, and retinopathy. Historically, universal methods to measure glycemic control for the diagnosis of diabetes included fasting plasma glucose level (FPG), 2-h plasma glucose (2HP), and random plasma glucose. However, these measurements did not provide information about glycemic control over a long period of time. To address this problem, there has been a switch in the past decade to diagnosing diabetes and its severity through measurement of blood glycated proteins such as Hemoglobin A1c (HbA1c) and glycated albumin (GA). Diagnosis and evaluation of diabetes using glycated proteins has many advantages including high accuracy of glycemic control over a period of time. Currently, common laboratory methods used to measure glycated proteins are high-performance liquid chromatography (HPLC), immunoassay, and electrophoresis. HbA1c is one of the most important diagnostic factors for diabetes. However, some reports indicate that HbA1c is not a suitable marker to determine glycemic control in all diabetic patients. GA, which is not influenced by changes in the lifespan of erythrocytes, is thought to be a good alternative indicator of glycemic control in diabetic patients. Here, we review the literature that has investigated the suitability of HbA1c, GA and GA:HbA1c as indicators of long-term glycemic control and demonstrate the importance of selecting the appropriate glycated protein based on the patient's health status in order to provide useful and modern point-of-care monitoring and treatment.

Multicenter evaluation of an enzymatic method for glycated albumin

BACKGROUND

The use of glycated albumin (GA) has been proposed as an additional glycemic control marker particularly useful in intermediate-term monitoring and in situation when HbA_1c test is not reliable.

METHODS

We have performed the first multicenter evaluation of the analytical performance of the enzymatic method quantILab Glycated Albumin assay implemented on the most widely used clinical chemistry analyzers (i.e. Abbott Architect C8000, Beckman Coulter AU 480 and 680, Roche Cobas C6000, Siemens ADVIA 2400 and 2400 XPT).

RESULTS

The repeatability of the GA measurement (expressed as CV, %) implemented in the participating centers ranged between 0.9% and 1.2%. The within-laboratory CVs ranged between 1.2% and 1.6%. A good alignment between laboratories was found, with correlation coefficients from 0.996 to 0.998. Linearity was confirmed in the range from 7.6 to 84.7%.

CONCLUSION

The new enzymatic method for glycated albumin evaluated by our investigation is suitable for clinical use.

Glycated albumin is superior to glycated hemoglobin for glycemic control assessment at an early stage of diabetes treatment: A multicenter, prospective study

AIMS

This study was to determine whether serum glycated albumin (GA) was a better indicator of glycemic control than hemoglobin A1c (HbA1c) when starting a new treatment regimen for type 2 diabetes.

METHODS

Newly diagnosed type 2 diabetes patients, or patients who had poor glycemic control with oral hypoglycemic agents, were enrolled at 10 hospitals in Beijing. Serum GA, HbA1c, fasting blood glucose (FBG), and C-peptide were assayed on Days 0, 14, 28, and 91 after treatment.

RESULTS

Four hundred ninety-nine patients were enrolled. Mean FBG, GA and HbA1c decreased significantly in patients at Days 14, 28, and 91. In patients with improved glycemic control, the reduction of GA and HbA1c levels was 10.5±13.3% vs. 5.1±5.4% on Day 14, 16.0±13.4% vs. 9.0±7.0% on Day 28, and 18.0±16.7% vs. 18.3±9.4% on Day 91, respectively, compared with baseline values. Changes in GA on Day 14, 28 and 91 were all closely correlated with changes in HbA1c on Day 91. Change in GA on Day 14 was correlated with treatment effectiveness evaluated by HbA1c on Day 91.

CONCLUSIONS

GA may be a useful marker for assessing glycemic control at an early stage of new diabetes treatment and assist in guiding adjustments to treatment and therapy.

Glycated albumin is associated with body mass index in euglycemic adults but is not predictive of postprandial blood glucose response

BACKGROUND

The level of glycated albumin in circulation is an indicator of blood glucose control over the preceding 2 weeks. It is not known if the level of glycated albumin in circulation relates to an individual's postprandial blood glucose response.

METHODS

Eighty-four euglycemic young adults (21.1 [3.9] years, BMI 23.9 [4.0] kg/m² ) primarily of European descent underwent a fasted meal test of 50 g carbohydrate from white bread. Capillary blood was then sampled at regular intervals over 2 hours. Correlations were sought between glycated albumin, fasted and 2-hour post-load blood glucose measurements, incremental area under the blood glucose curve, glycemic range, body mass index (BMI), and C-reactive protein (CRP).

RESULTS

When adjusted for age and sex, glycated albumin was inversely correlated with BMI (r=-.25, P=.027). No significant correlations existed for glycated albumin and postprandial markers of blood glucose control. BMI and CRP values correlate in this population (r=.30, P=.009).

CONCLUSIONS

Glycated albumin in circulation is not related to postprandial blood glucose response in young euglycemic adults. Glycated albumin is lower in euglycemic adults with higher BMI values. Contrary to research with older adults or those with impaired glucose control, glycated albumin did not correlate to CRP.

Graphene based aptasensor for glycated albumin in diabetes mellitus diagnosis and monitoring

We selected and modified DNA aptamers specifically bound glycated human serum albumin (GHSA), which is an intermediate marker for diabetes mellitus. Our aptamer truncation study indicated that the hairpin-loop structure with 23 nucleotides length containing triple G-C hairpins and 15-nucleotide loop, plays an important role in GHSA binding. Fluorescent quenching graphene oxide (GO) and Cy5-labeled G8 aptamer were used in this study to develop simple and sensitive graphene based aptasensor for GHSA detection. The limit of detection (LOD) of our aptasensor was 50 μg/mL, which was lower than other existing methods. In addition, with the nuclease resistance system, our GHSA detection platform could also be used in clinical samples. Importantly, our approach could significantly reveal the higher levels of GHSA concentrations in diabetes than normal serums. These indicate that our aptasensor has a potential for diagnosis and monitoring of diabetes mellitus.

Measurement of glycated albumin in serum and plasma by LC-MS/MS

BACKGROUND

Diagnosis of diabetes and monitoring of long-term blood sugar are preferably done by measurement of glycated hemoglobin (HbA1c). Diabetic patients with end stage renal disease (ESRD) may have short-lived red blood cells due to hemodialysis (HD), and thus higher turnover of hemoglobin. The level of glycated hemoglobin (HbA1c) may be lower than expected for these patients, even at increased blood glucose, possibly making glycated albumin (GA) measurement a better alternative.

METHODS

The percentage of GA was measured by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Fast and efficient trypsin digestion of proteins in diluted serum or plasma resulted in a high number of proteotypic peptides from albumin, including KQTALVELVK which was detected both glycated and non-glycated by multiple reaction monitoring (MRM). The percentage of GA was estimated by neat peak area response of glycated peptide divided by the sum of glycated and non-glycated peptide.

RESULTS

Acceptable method reproducibility (6% CV), repeatability (2-6% CV), limit of quantification (0.75% GA), linearity (R(2) = 0.999) and recovery (79 ± 9%) was achieved without using calibration or isotope-labeled internal standard. GA was strongly correlated with HbA1c (r = 0.84) for patients without ESRD. The average ratio of GA/HbA1c was significantly higher (p = 0.0021) for ESRD patients (1.84 ± 0.38, n = 62) compared to other patients (1.67 ± 0.28, n = 225).

CONCLUSION

GA measurement by detecting glycation in KQTALVELVK with LC-MS/MS seems to be a useful supplement to HbA1c for detecting increased blood glucose in diabetic patients with ESRD.

GLYCATED ALBUMIN AT 4 WEEKS CORRELATES WITH A1C LEVELS AT 12 WEEKS AND REFLECTS SHORT-TERM GLUCOSE FLUCTUATIONS

OBJECTIVE

Evaluate the performance of glycated albumin (GA) monitoring by comparing it to other measures of glycemic control during intensification of antidiabetic therapy.

METHODS

This 12-week, prospective, multicenter study compared the diagnostic clinical performance of GA to glycated hemoglobin A1C (A1C), fructosamine corrected for albumin (FRA), fasting plasma glucose (FPG), and mean blood glucose (MBG) estimated from self-monitoring of blood glucose (SMBG) and continuous glucose monitoring (CGM) in 30 patients with suboptimally controlled type 1 or 2 diabetes.

RESULTS

Mean A1C decreased from 9.5% to 8.1%. Mean SMBG correlated closely with CGM (Pearson r = 0.783 for daily estimates and r = 0.746 for weekly estimates, P<.0001). Both GA and FRA levels significantly correlated with changes from baseline in A1C and mean weekly SMBG (P<.001). The lowest observed median GA occurred at 4 weeks, followed by a small increase and then a slight reduction, mirroring changes in overall mean SMBG values. The median A1C fell throughout the treatment period, failing to reflect short-term changes in SMBG. A ≥1% reduction in GA at 4 weeks was significantly associated with a ≥0.5% change in A1C at 12 weeks (odds ratio [OR] = 19.0, 95% confidence interval [CI]: 1.4, 944, P = .018).

CONCLUSION

In patients receiving glucose-lowering therapy, changes in GA at 4 weeks were concordant with changes in A1C at 12 weeks, and both GA and FRA more accurately reflected short-term blood glucose fluctuations than A1C.

Association between glycemic control and birthweight with glycated albumin in Chinese women with gestational diabetes mellitus

Aims/Introduction

To assess glycated albumin (GA) as a potential glycemic index in managing gestational diabetes mellitus (GDM).

Materials and Methods

Eligible pregnant women were divided into the GDM group with abnormal result on a 75‐g oral glucose tolerance test (OGTT) and the control (normal) group. GA measurements, Pearson's correlation analysis, multiple logistic regression and receiver operating characteristic curve analysis were obtained at the follow‐up examination of participants in the two groups.

Results

A total of 2,118 women were assigned to the GDM group (n = 639) and control group (n = 1,479). The mean level of serum GA in GDM group was significantly greater than that in the control group at both 24–28 and 36–38 weeks of gestation (P < 0.05). The area under the receiver operating characteristic curve for GA defining good glycemic control in GDM was 0.874 (95% confidence interval 0.811–0.938). The cut‐off point for the GA levels derived from the receiver operating characteristic curve was 11.60%, which had sensitivity and specificity for detecting a poor glycemic status of 75.93% and 86.36%, respectively. The risk of birthweight ≥3,500 g and macrosomia increased significantly with GA levels ≥13.00% at 24–28 weeks and ≥12.00% at 36–38 weeks of gestation.

Conclusions

GA might be an appropriate and conveniently measured index that can detect poor glycemic control and predict birthweights in GDM women.

Determinants of fructosamine levels in a multi-ethnic Sub-Saharan African population

BACKGROUND AND PURPOSE

Fructosamine provides an estimate of diabetes control over a shorter period than HbA1c, and has been proposed as a suitable parameter to monitor glycemic control in low-income countries. The aim of this study was to investigate determinants of fructosamine levels in an urban non-diabetic population of Cameroon.

METHODS

This was a cross-sectional study including 437 healthy adults with no known history of diabetes mellitus, aged 40 years and above, recruited from the ten administrative regions, representing major ethnic groups in the country. Plasma glucose and fructosamine were measured after an overnight fasting. Univariable and multivariable analyses were used to investigate the factors associated with fructosamine measurements.

RESULTS

Fructosamine levels ranged from 68.2 to 940.8 μmol/l with a mean (standard deviation) of 294.4 (131.3) μmol/l. These levels varied significantly across regions and were higher in men than in women (p=0.001) and in those with screen-detected diabetes than in those with normoglycemia (p<0.0001). There was a negative correlation between fructosamine and body mass index (r=-0.15, p=0.009), and a positive correlation with fasting plasma glucose (FPG) (r=0.37, p<0.0001) and total bilirubinemia (r=0.21, p<0.0001). In multivariable model, sex, BMI, FPG, total bilirubine and screen-detected diabetes were no longer associated with fructosamine levels.

CONCLUSION

Fructosamine was not independently associated with age, sex, ethnicity, and the glycemic status. Further studies need to be carried out to better elucidate all the factors determining the measurement of fructosamine in order to accurately interpret its values in diabetic populations.

Serum glycated albumin predicts the progression of diabetic retinopathy--a five year retrospective longitudinal study

AIMS

To assess the predictive value of glycated albumin (GA) and other risk factors on a progression of diabetic retinopathy (DR).

METHODS

In this retrospective longitudinal study, we enrolled the subjects with type 2 diabetes who had undergone fundus photography twice with a 5-years gap between January 2006 and December 2012, and had been measured consecutively for hemoglobin A1c (HbA1c) and GA levels every 3 or 6 months. The subjects were divided into two groups with or without a progression of DR. The mean HbA1c and mean GA were calculated separately by the sum of all measured values divided by the numbers of values throughout the study period.

RESULTS

Of the 359 subjects, progression group showed significantly higher diabetes duration (8.41±5.72 vs. 6.46±5.77, P<0.01), baseline HbA1c (9.13±2.71 vs. 8.41±2.32, P<0.05), fasting plasma glucose (8.71±2.78 vs. 7.94±2.63, P<0.05), 2h-postprandial glucose (15.12±11.20 vs.13.14±4.72, P<0.05), eGFR (114.81±39.15 vs. 103.23±32.18, P<0.01), mean HbA1c (8.32±1.69 vs. 7.39±1.35, P<0.01) and mean GA (22.66±5.92 vs. 19.83±5.18, P<0.01) than non-progression group. The frequencies of subjects with DR progression increased obviously with the increment of baseline HbA1c, mean HbA1c and mean GA according to quartile stratification of the above three glucose parameters. Multivariable binary logistic regression analysis investigated that the factors affected the DR progression were the presence of DR at baseline (OR=0.391, P=0.005), mean HbA1c (OR=1.389, P=0.021), mean GA (OR=1.087, P=0.039) and eGFR (OR=1.008, P=0.045). The optimal cut-off values of mean HbA1c and GA to predict DR progression were 7.27% and 21.85%, respectively.

CONCLUSIONS

The presence of DR at baseline, poor glycemic control, glycated albumin, and impaired renal function predicted DR progression in patients with type 2 diabetes.