Evaluation of biological variation of glycated albumin (GA) and fructosamine in healthy subjects

Preventing the Impact of Hyperglycemia and Diabetes on Patients Undergoing Total Joint Arthroplasty

Primary and revision total joint arthroplasty (TJA) procedures have become increasingly popular worldwide. At the same time, a growing number of patients undergoing TJA are either known diabetics or exhibit evidence of hyperglycemia preoperatively. Based on extensive data, it is well-established that poor glycemic control in TJA patients is an independent risk factor for several complications, including periprosthetic joint infection and death. This article will serve as an overview of currently available evidence on how to prevent the impact of hyperglycemia and diabetes mellitus on patients undergoing TJA.

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.

Reference intervals for glycated albumin during physiological pregnancy of Europid women: Evidences from a prospective observational study

BACKGROUND AND AIMS

Glycated albumin (GA) may assess glycometabolic control over a short period of time respect to HbA_1c, and its use to screen for gestational diabetes in pregnancy has been suggested. To this regard few data on reference intervals (RI) for GA on Europid women have been collected, only from cross-sectional investigations. Aim of this work has been to collect trimester-specific RI for GA in physiological pregnancies, following a longitudinal prospective study.

METHODS

Forty-five healthy pregnant Europid women have been enrolled for whom a GDM screening test was scheduled at 24-28 weeks, in 5 different Italian centers. Only those negative to the OGTT were included. The women had 4 successive visits at 6-10 weeks of gestation, at 16-18 weeks, at 24-28 weeks and at the end of pregnancy. ALT, AST, total bilirubin, C-reactive protein, cholinesterase, creatinine, GGT, glycated albumin, iron, total serum proteins, transferrin were measured in duplicate on aliquots of serum samples by a central laboratory.

RESULTS

The RI (2.5-97.5 percentiles) for GA were 11.1-14.8 % (I visit), 10.9-15.6 % (II visit), 10.6-14.1 % (III visit) and 10.7-14.3 % (IV visit). The RI of other biomarkers confirmed previously published data. The RI for serum cholinesterase we present are novel, and were 5049-9906 U/L (Iv), 4212-8965 U/L (IIv), 3518-8470 U/L (IIIv) and 3945-8727 U/L (IVv).

CONCLUSIONS

Trimester-specific RI are important for using GA and serum cholinesterase in pregnancy. However, considering the high inter-individual variability of both markers, the use of longitudinal interpretations of the individual variations of both proteins during pregnancy should be preferred.

Assessment of Hyperglycemia, Hypoglycemia and Inter-Day Glucose Variability Using Continuous Glucose Monitoring among Diabetic Patients on Chronic Hemodialysis

Continuous glucose monitoring (CGM) facilitates the assessment of short-term glucose variability and identification of acute excursions of hyper- and hypo-glycemia. Among 37 diabetic hemodialysis patients who underwent 7-day CGM with the iPRO2 device (Medtronic Diabetes, Northridge, CA, USA), we explored the accuracy of glycated albumin (GA) and hemoglobin A1c (HbA1c) in assessing glycemic control, using CGM-derived metrics as the reference standard. In receiver operating characteristic (ROC) analysis, the area under the curve (AUC) in diagnosing a time in the target glucose range of 70–180 mg/dL (TIR^70–180) in <50% of readings was higher for GA (AUC: 0.878; 95% confidence interval (CI): 0.728–0.962) as compared to HbA1c (AUC: 0.682; 95% CI: 0.508–0.825) (p < 0.01). The accuracy of GA (AUC: 0.939; 95% CI: 0.808–0.991) in detecting a time above the target glucose range > 250 mg/dL (TAR^>250) in >10% of readings did not differ from that of HbA1c (AUC: 0.854; 95% CI: 0.699–0.948) (p = 0.16). GA (AUC: 0.712; 95% CI: 0.539–0.848) and HbA1c (AUC: 0.740; 95% CI: 0.570–0.870) had a similarly lower efficiency in detecting a time below target glucose range < 70 mg/dL (TBR^<70) in >1% of readings (p = 0.71). Although the mean glucose levels were similar, the coefficient of variation of glucose recordings (39.2 ± 17.3% vs. 32.0 ± 7.8%, p < 0.001) and TBR^<70 (median (range): 5.6% (0, 25.8) vs. 2.8% (0, 17.9)) were higher during the dialysis-on than during the dialysis-off day. In conclusion, the present study shows that among diabetic hemodialysis patients, GA had higher accuracy than HbA1c in detecting a 7-day CGM-derived TIR^70–180 < 50%. However, both biomarkers provided an imprecise reflection of acute excursions of hypoglycemia and inter-day glucose variability.

Associations of glycated albumin and fructosamine with glycaemic status in urban black South Africans

BACKGROUND

The associations of glycated albumin (GA) and fructosamine (FA) as alternate tests for diabetes screening in South Africans were examined to overcome shortcomings with oral glucose tolerance tests (OGTTs).

METHODS

Based on OGTTs, glycaemic status included 1) normal glucose, 2) dysglycaemia (impaired fasting glucose, impaired glucose tolerance, newly diagnosed diabetes), and 3) known diabetes.

RESULTS

Among 1092 participants, >21 years, mean GA (16.9%) and FA (230.2 μmol/l) increased significantly by age and worsening glycaemic status and were significantly higher in women vs. men and BMI (kg/m²) ≥ 30 vs. <30. For dysglycaemia, correlations of GA and FA with fasting and 2-hour glucose levels were higher in obese (0.576 to 0.688) vs. non-obese (-0.010 to 0.522). Optimal GA threshold to identify dysglycaemia was 15.35% and comparable, but with lower sensitivity (0.54) and specificity (0.55), to Asian studies. For FA, the optimal cut-point of 227.0 μmol/l approximated that described in the literature. Dysglycaemia and known diabetes were associated with GA, while only known diabetes was related to FA, in models adjusted for age, gender and obesity.

CONCLUSIONS

Potential exists for GA and/or FA as alternative measures of dysglycaemia in clinical practice in Africans, but longitudinal studies are required to clearly elucidate their utility.

Evaluación crítica y meta-análisis de estudios de variación biológica para albúmina glicosilada, glucosa y HbA1c

Objetivos

A lo largo de los años se han publicado numerosos artículos sobre variación biológica (VB) de diferente calidad. Los objetivos de este trabajo fueron realizar una revisión sistemática y una evaluación crítica de los estudios de VB para albúmina glicosilada y proporcionar datos actualizados de VB para glucosa y HbA_1c, incluyendo prestigiosos estudios recientemente publicados como el Estudio de Variación Biológica Europea (EuBIVAS).

Métodos

Se hizo una búsqueda bibliográfica sistemática para identificar estudios sobre VB, encontrándose 9 estudios no incluidos en la primera revisión: 4 para albúmina glicosilada, 3 para glucosa y 3 para HbA_1c. Se realizó una evaluación crítica de los estudios relevantes, utilizando la herramienta Biological Variation Data Critical Appraisal Checklist (BIVAC). Se obtuvieron los estimados globales de VB mediante meta-análisis de los estudios que cumplían los requisitos BIVAC, realizados en individuos sanos con estudios de diseño similar.

Resultados

Un estudio recibió el grado A, dos el B y 6 el C. en la mayoría de los casos el grado C se asoció a deficiencias en el análisis estadístico de los datos. Los estimados de VB para albúmina glicosilada fueron: CV_I = 1,4%(1,2–2,1) y CV_G = 5,7%(4,7–10,6); para HbA_1c, CV_I = 1,2%(0,3–2,5), CV_G = 5,4%(3,3–7,3) y para glucosa, CV_I = 5,0%(4,1–12,0), CV_G = 8,1%(2,7–10,8) no difirieron de los estimados globales previamente descritos.

Conclusiones

La evaluación crítica y clasificación de los estudios de VB a tenor de su calidad metodológica, seguido de un meta-análisis, genera estimados de VB robustos y fiables. Este estudio proporciona datos de VB para albúmina glicolisada, glucosa y HbA_1c actualizados y basados en la evidencia científica.

Critical appraisal and meta-analysis of biological variation studies on glycosylated albumin, glucose and HbA1c

OBJECTIVES

Numerous biological variation (BV) studies have been performed over the years, but the quality of these studies vary. The objectives of this study were to perform a systematic review and critical appraisal of BV studies on glycosylated albumin and to deliver updated BV estimates for glucose and HbA_1c, including recently published high-quality studies such as the European Biological Variation study (EuBIVAS).

METHODS

Systematic literature searches were performed to identify BV studies. Nine publications not included in a previous review were identified; four for glycosylated albumin, three for glucose, and three for HbA_1c. Relevant studies were appraised by the Biological Variation Data Critical Appraisal Checklist (BIVAC). Global BV estimates were derived by meta-analysis of BIVAC-compliant studies in healthy subjects with similar study design.

RESULTS

One study received BIVAC grade A, 2B, and 6C. In most cases, the C-grade was associated with deficiencies in statistical analysis. BV estimates for glycosylated albumin were: CV_I=1.4% (1.2-2.1) and CV_G=5.7% (4.7-10.6), whereas estimates for HbA_1c, CV_I=1.2% (0.3-2.5), CV_G=5.4% (3.3-7.3), and glucose, CV_I=5.0% (4.1-12.0), CV_G=8.1% (2.7-10.8) did not differ from previously published global estimates.

CONCLUSIONS

The critical appraisal and rating of BV studies according to their methodological quality, followed by a meta-analysis, generate robust, and reliable BV estimates. This study delivers updated and evidence-based BV estimates for glycosylated albumin, glucose and HbA_1c.

Review of methods for detecting glycemic disorders

Prediabetes (intermediate hyperglycemia) consists of two abnormalities, impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) detected by a standardized 75-gram oral glucose tolerance test (OGTT). Individuals with isolated IGT or combined IFG and IGT have increased risk for developing type 2 diabetes (T2D) and cardiovascular disease (CVD). Diagnosing prediabetes early and accurately is critical in order to refer high-risk individuals for intensive lifestyle modification. However, there is currently no international consensus for diagnosing prediabetes with HbA1c or glucose measurements based upon American Diabetes Association (ADA) and the World Health Organization (WHO) criteria that identify different populations at risk for progressing to diabetes. Various caveats affecting the accuracy of interpreting the HbA1c including genetics complicate this further. This review describes established methods for detecting glucose disorders based upon glucose and HbA1c parameters as well as novel approaches including the 1-hour plasma glucose (1-h PG), glucose challenge test (GCT), shape of the glucose curve, genetics, continuous glucose monitoring (CGM), measures of insulin secretion and sensitivity, metabolomics, and ancillary tools such as fructosamine, glycated albumin (GA), 1,5- anhydroglucitol (1,5-AG). Of the approaches considered, the 1-h PG has considerable potential as a biomarker for detecting glucose disorders if confirmed by additional data including health economic analysis. Whether the 1-h OGTT is superior to genetics and omics in providing greater precision for individualized treatment requires further investigation. These methods will need to demonstrate substantially superiority to simpler tools for detecting glucose disorders to justify their cost and complexity.

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.

Glycated albumin as a glycaemic marker in patients with advanced chronic kidney disease and anaemia: a preliminary report

Background: The association between glycated albumin (GA) and glycaemic status has not been fully described in patients with advanced chronic kidney disease (CKD) in relation to anaemia. The aim of this study was to evaluate the relationship between GA and fasting plasma glucose (FPG) and HbA1c in patients with advanced CKD and to evaluate the influence of anaemia in such relationship. Materials and methods: Patients with CKD stage 4 or 5 were included in the study. eGFR was calculated by the CKD-EPI creatinine equation. Plasma GA was measured by an enzymatic method. Results: Eighty-one patients were included in the study, 46 (57%) were males; the mean age was 67 ± 14 years. HbA1c was correlated with Hb (r = 0.39; p = .0003), and no significant correlation was detected between plasma GA and serum albumin (p = .82). A significant association between FPG and GA (r² = 0.41; p < .0001), and between FPG and HbA1c (r² = 0.42; p < .0001) was detected in the whole study population. Patients with moderate/severe anaemia had lower HbA1c than patients with no anaemia, while both FPG and GA were comparable between the two groups. Multivariate regression analysis showed that GA was a significant predictor of FPG in patients with moderate/severe anaemia while HbA1c did not (r² = 0.55; p < .0001 for the model). Conclusions: GA, alone or in combination with other biomarkers, can be considered for the evaluation of glycaemic status in patients with advanced CKD and severe anaemia.

Glycated serum proteins: High in pancreatic cancer and low in preeclampsia

Glycated serum protein (GSP, measured as serum fructosamine concentration in μmol/L) is a product of glycation reaction between glucose and serum proteins in the blood circulation. GSP is used along with blood glucose, glycated hemoglobin (HbA1c), and glycated albumin as indicators of glycemic control for diabetic patients. However, a systematic comparison of the GSP levels in different types of human diseases has not been reported. In this study, 62,698 clinical lab test results of GSP levels in patients with 61 clinically defined diseases over the past 5 years in our hospital were retrieved and compared to that of 1861 clinical lab test results in healthy individuals. Based on the mean (SD), median, and p (-Log₁₀p) values, we found that patients with type 2 diabetes, hepatic encephalopathy, pancreatic cancer, healthy individuals >65 years old, and cerebral arteriosclerosis had significantly (p<0.05, -Log₁₀p>1.30) increased whereas patients with 49/61 diseases including preeclampsia, nephrotic syndrome, sepsis, lupus erythematous, and leukemia had significantly decreased GSP levels compared to that of healthy controls. Among the 61 diseases, type 2 diabetes and leukemia had the highest -Log₁₀p values (>274) and lupus erythematous, nephrotic syndrome, and gastric cancer had -Log₁₀p values >140. Revealing the molecular mechanisms especially those underlying the decreased GSP levels in most of human diseases might make GSP levels serve more clinical purposes in future.

Evaluation of biological variation of glycated hemoglobin and glycated albumin in healthy Chinese subjects

Background

Glycated hemoglobin (HbA1c) and glycated serum albumin (GSA) are used to evaluate the mean blood glucose levels. To ensure safe clinical application of HbA1c and GSA, reliable biological variation (BV) data are required. The aim of this research was to define the BV of HbA1c and GSA employing stringent rules.

Methods

Blood samples were drawn from 19 healthy subjects (10 females, nine males) once per week for 5 weeks. All samples were analyzed using enzymatic method for GSA and HPLC for HbA1c. The data were assessed for outliers, normality and variance homogeneity, and coefficient of variation (by ANOVA) for BV. Sex‐stratified BV including within‐subject (CV_I) and between‐subject (CV_G) was defined for HbA1c and GSA.

Results

The following estimates for BV values for CV_I and CV_G, respectively, were GSA: 1.23% and 4.67%, Alb: 0.75% and 3.18%, and HbA1c: 0.12% and 2.91%. The RCV of GSA was 3.61%, and HbA1c was 1.41%. And the II was 0.26 for GSA, and 0.07 for HbA1c, both of them less than 0.6. According to the 95% CI, the CV_I of HbA1c was statistically different between females and males. And both the CV_G of HbA1c and GSA were statistically different between females and males.

Conclusion

All CV_I and CV_G estimates were lower than those reported in the online BV database. And there is a significant difference between males and females. Analytical performance specifications derived from BV of this research can be applied internationally.

Performance of glycated albumin for type 2 diabetes and prediabetes diagnosis in a South African population

OBJECTIVE

To assess the utility of glycated albumin (GA%) as a diagnostic marker of type 2 diabetes and prediabetes in an African population.

METHODS

GA% levels were determined in a sample of 1294 mixed ancestry adults (74.2% women) residing in Cape Town using an enzymatic method. The participants' glycemic status was based on oral glucose tolerance test (OGTT).

RESULTS

The mean age was 47.8 years with a mean body mass index (BMI) of 28.7 kg/m². Obesity was more pronounced in the screen-detected diabetes and prediabetes groups with mean BMI's of 32.5 kg/m² and 31.5 kg/m² respectively. The optimal thresholds of GA% to diagnose screen-detected diabetes and prediabetes, were 14.90% and 12.75% respectively. For screen-detected diabetes, the C-statistic was higher for HbA1c than GA% (p = .034) with values of 0.899 (95% CI 0.855-0.943) and 0.873 (0.782-0.892) respectively. The agreement between GA% and HbA1c at their optimal thresholds for diagnosing screen-detected diabetes, was kappa = 0.33 (95% CI 0.26-0.40) and was higher than the agreement for prediabetes, kappa = 0.16 (0.11-0.21). The performance of GA% to identify screen-detected diabetes at the optimal threshold of 14.90%, was 64.8% (95% CI 54.1%-74.6%) for sensitivity and 93.5% (92.0%-94.9%) for specificity. GA% was significantly less sensitive, but more specific than HbA1c (at the optimal threshold of 6.15%) for screen-detected diabetes diagnosis (both p ≤ .002 from McNemar tests for sensitivity and specificity comparisons).

CONCLUSIONS

GA% performed less well than HbA1c to identify participants with OGTT-diagnosed type 2 diabetes or prediabetes (HbA1c cut-off of 6.15% and 5.95% respectively) in this population.

Comparison of Glycemic Markers in Chronic Hemodialysis Using Continuous Glucose Monitoring

BACKGROUND

Glycated hemoglobin A1c (HbA1c) among diabetic hemodialysis patients continues to be the standard of care, although its limitations are well recognized. This study evaluated glycated albumin (GA) and glycated serum protein (GSP) as alternatives to HbA1c in detecting glycemic control among diabetic hemodialysis patients using continuous-glucose-monitoring (CGM)-derived glucose as reference standard.

METHODS

A CGM system (iPRO) was applied for 7 days in 37 diabetic hemodialysis patients to determine glycemic control. The accuracy of GA and GSP versus HbA1c in detecting a 7-day average glucose ≥184 mg/dL was evaluated via receiver-operating-characteristic (ROC) analysis.

RESULTS

CGM-derived glucose exhibited strong correlation (r = 0.970, p < 0.001) and acceptable agreement with corresponding capillary glucose measurements obtained by the patients themselves in 1,169 time-points over the 7-day-long CGM. The area under ROC curve (AUC) for GA, GSP, and HbA1c to detect poor glycemic control was 0.976 (0.862-1.000), 0.682 (0.502-0.862), and 0.776 (0.629-0.923) respectively. GA levels >20.3% had 90.9% sensitivity and 96.1% specificity in detecting a 7-day average glucose ≥184 mg/dL. The AUC for GA was significantly higher than the AUC for GSP (difference between areas: 0.294, p < 0.001) and the AUC for HbA1c (difference between areas: 0.199, p < 0.01).

CONCLUSION

Among diabetic hemodialysis patients, GA is a stronger indicator of poor glycemic control assessed with 7-day-long CGM when compared to GSP and HbA1c.

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.

Variations in native protein glycation and plasma antioxidants in several birds of prey

Birds are an anomaly among vertebrates as they are remarkably long-lived despite having naturally high blood glucose and metabolic rates. For mammals, hyperglycemia leads to oxidative stress and protein glycation. In contrast, many studies have shown that domestic and wild birds are relatively resistant to these glucose-mediated pathologies. Surprisingly very little research has examined protein glycation in birds of prey, which by nature consume a diet high in protein and fat that promotes gluconeogenesis. The purpose of this study was to evaluate protein glycation and antioxidant concentrations in serum samples from several birds of prey (bald eagle (BAEA), red-tailed hawk (RTHA), barred owl (BAOW), great horned owl (GHOW)) as protein glycation can accelerate oxidative stress and vice versa. Serum glucose was measured using a commercially available assay, native albumin glycation was measured by mass spectrometry and various antioxidants (uric acid, vitamin E, retinol and several carotenoids) were measured by high performance liquid chromatography. Although glucose concentrations were not significantly different between species (p=0.340), albumin glycation was significantly higher (p=0.004) in BAEA (23.67±1.90%) and BAOW (24.28±1.43%) compared to RTHA (14.31±0.63%). Of the antioxidants examined, lutein was significantly higher in BAOW (p=0.008). BAEA had the highest beta-cryptoxanthin and beta-carotene concentrations (p<0.005). The high concentrations of antioxidants in these birds of prey relative to other birds likely helps protect from complications that may otherwise arise from having high glucose and protein glycation.

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.

The establishment of biological reference intervals of nontraditional glycemic markers in a Chinese population

BACKGROUND

We established the reference intervals for glycated albumin (GA), fructosamine (FA), and 1,5-anhydroglucitol (1,5-AG) in a Chinese healthy population.

METHODS

This study enrolled a total of 458 eligible reference individuals, consisted of 226 men and 232 women, aged from 20~79 years (median age 43 years), who attending routine healthy checks. We stratified the subjects according to gender (males and females) and age (20-39, 40-59, and 60-79 years), and combined statistical methods with Lahti algorithm, as well as appropriate clinical consideration, to judge whether partitioning for data was needed.

RESULTS

Glycated albumin levels between males and females were statistically different (P<.001), but the absolute difference between the upper reference limits was only 0.31%, which was too small to be clinically relevant. GA levels across the three age groups were statistically different (P<.001), and Lahti algorithm suggested partitioning for 20-59 and 60-79 years, which reference intervals were 10.38%-13.89% and 10.23%-14.79%, respectively. 1,5-AG levels in males were significant higher than females (P<.001), and absolute difference was 51 μmol/L (8.5 μg/mL) in mean level. Thus, partitioning for gender was needed. Reference intervals for 1,5-AG were 107-367 μmol/L for males and 79-306 μmol/L for females. The absolute difference of the lower reference limits for FA was only 7 μmol/L between males and females. FA levels across the three age groups were not statistically different (P>.05). The reference interval for FA was 220-298 μmol/L.

CONCLUSION

New reference intervals for nontraditional glycemic markers were established based on a Chinese population.

Pregnancy diabetes: A comparison of diagnostic protocols based on point-of-care, routine and optimized laboratory conditions

In vitro glycolysis poses a problem during diabetes screening, especially in remote laboratories. Point-of-care analysis (POC) may provide an alternative. We compared POC, routine and STAT analysis and a feasible protocol during glucose tolerance test (GTT) for pregnancy diabetes (GDM) screening. In the routine protocol, heparin tubes were used and turn-around-time (TAT) was unsupervised. In the STAT protocol, tubes were processed immediately. The feasible protocol comprised of citrated tubes with a TAT of 1 hour. Outcome was defined as glucose concentration and clinical diagnosis. Glucose measured by POC was higher compared to routine analysis at t = 0 (0.25 mM) and t = 120 (1.17 mM) resulting in 17% more GDM diagnoses. Compared to STAT analysis, POC glucose was also higher, although less pronounced (0.06 and 0.9 mM at t = 0 and t = 120 minutes, respectively) and misclassification was only 2%. Glucose levels and clinical diagnosis were similar using the feasible protocol and STAT analysis (0.03 mM and −0.07 mM at t = 0 and t = 120, 100% identical diagnoses). POC is an viable alternative for STAT glucose analysis in GDM screening (sensitivity: 100%, specificity: 98%). A feasible protocol (citrated phlebotomy tubes with a TAT of 60 minutes) resulted in 100% identical outcome and provides the best alternative.

Advantages and pitfalls of fructosamine and glycated albumin in the diagnosis and treatment of diabetes

The efficient diagnosis and accurate monitoring of diabetic patients are cornerstones for reducing the risk of diabetic complications. The current diagnostic and prognostic strategies in diabetes are mainly based on two tests, plasma (or capillary) glucose and glycated hemoglobin (HbA1c). Nevertheless, these measures are not foolproof, and their clinical usefulness is biased by a number of clinical and analytical factors. The introduction of other indices of glucose homeostasis in clinical practice such as fructosamine and glycated albumin (GA) may be regarded as an attractive alternative, especially in patients in whom the measurement of HbA1c may be biased or even unreliable. These include patients with rapid changes of glucose homeostasis and larger glycemic excursions, and patients with red blood cell disorders and renal disease. According to available evidence, the overall diagnostic efficiency of GA seems superior to that of fructosamine throughout a broad range of clinical settings. The current method for measuring GA is also better standardized and less vulnerable to preanalytical variables than those used for assessing fructosamine. Additional advantages of GA over HbA1c are represented by lower reagent cost and being able to automate the GA analysis on many conventional laboratory instruments. Although further studies are needed to definitely establish that GA can complement or even replace conventional measures of glycemic control such as HbA1c, GA may help the clinical management of patients with diabetes in whom HbA1c values might be unreliable.

Diet and glycaemia: the markers and their meaning. A report of the Unilever Nutrition Workshop

Consumption of carbohydrate-containing foods leads to transient postprandial rises in blood glucose concentrations that vary between food types. Higher postprandial glycaemic exposures have particularly been implicated in the development of chronic cardiometabolic diseases. Reducing such diet-related exposures may be beneficial not only for diabetic patients but also for the general population. A variety of markers have been used to track different aspects of glycaemic exposures, with most of the relevant knowledge derived from diabetic patients. The assessment of glycaemic exposures among the non-diabetic population may require other, more sensitive markers. The present report summarises key messages of presentations and related discussions from a workshop organised by Unilever intended to consider currently applied markers of glycaemic exposure. The particular focus of the meeting was to identify the potential applicability of glycaemic exposure markers for studying dietary effects in the non-diabetic population. Workshop participants concluded that markers of glycaemic exposures are sparsely used in intervention studies among non-diabetic populations. Continuous glucose monitoring remains the optimal approach to directly assess glycaemic exposure. Markers of glycaemic exposure such as glycated Hb, fructosamine, glycated albumin, 1,5-anhydroglucitol and advanced glycation end products can be preferred dependent on the aspect of interest (period of exposure and glucose variability). For all the markers of glycaemia, the responsiveness to interventions will probably be smaller among the non-diabetic than among the diabetic population. Further validation and acceptance of existing glycaemic exposure markers applied among the non-diabetic population would aid food innovation and better design of dietary interventions targeting glycaemic exposure.

The ratio of estimated average glucose to fasting plasma glucose level is superior to glycated albumin, hemoglobin A1c, fructosamine, and GA/A1c ratio for assessing β-cell function in childhood diabetes

Objective. This study investigated the use of the estimated average glucose to fasting plasma glucose ratio (eAG/fPG ratio) to screen for β-cell function in pediatric diabetes. Methods. Glycated hemoglobin (HbA1c), glycated albumin (GA), fructosamine, insulin, and C-peptide levels were measured. The ratio of GA to HbA1c (GA/A1c ratio) was calculated, and the homeostasis model assessment of β-cell function (HOMA-β) was determined. Results. Median values of C-peptide, insulin, and HOMA-β levels were significantly higher in patients with an increased eAG/fPG ratio than in those with a decreased eAG/fPG ratio. C-peptide and HOMA-β levels were more closely correlated with the eAG/fPG ratio than with GA, HbA1c, the GA/A1c ratio, and fructosamine. In contrast, body mass index was significantly associated with GA, GA/A1c ratio, and fructosamine, but not with the eAG/fPG ratio and HbA1c levels. To test the diagnostic accuracies of the eAG/fPG ratio for identifying HOMA-β > 30.0% in patients with type 2 diabetes, the area under the ROC curve of the eAG/fPG ratio was significantly larger than that of the GA/A1c ratio [0.877 (95% CI, 0.780–0.942) versus 0.775 (95% CI, 0.664–0.865), P = 0.039]. Conclusions. A measurement of the eAG/fPG ratio may provide helpful information for assessing β-cell function in pediatric patients with diabetes.

[Assays of HbA1c and Amadori products in human biology]

Different Amadori products, formed during the early steps of the non-enzymatic glycation of proteins, may be assayed in current practice in human biology. The most important marker is HbA1c, resulting from the binding of glucose to the N-terminal extremity of HbA beta chains. HbA1c may be evaluated by various techniques (ion exchange or affinity high performance liquid chromatography, capillary electrophoresis, immunoassay, enzymatic technique) and is considered the best marker of diabetic patient survey. Due to its irreversible and cumulative formation, it provides a retrospective information on the glycemic balance over the four to eight weeks preceding blood collection. It benefits from an international standardization, based on a reference method using liquid chromatography coupled to capillary electrophoresis or mass spectrometry, maintained by an international network of reference laboratories. When HbA1c assay cannot be used (anemia, hemolysis, hemoglobinopathy) or when a shorter period of glycemic equilibrium must be evaluated (child and adolescent, pregnancy, therapeutic changes), other Amadori products may be assayed, like plasma fructosamine (all plasma glycated proteins) or glycated albumin. Nevertheless, these assays are less used in practice, because their semiological value has been less evidenced. Besides, fructosamine assay lacks specificity, and glycated albumin assay has been described recently. An expanding use of HbA1c assay is expected, especially for the diagnosis of diabetes mellitus and the evaluation of other risks, especially cardiovascular ones.