Analytical performances of a new enzymatic assay for hemoglobin A1c

Increases in Psychological Stress Are Associated With Higher Fasting Glucose in US Chinese Immigrants

BACKGROUND

The majority of Chinese Americans is foreign-born, and it is well-documented that immigration to the United States (US) leads to increased risk for chronic diseases including type 2 diabetes. Increased disease risk has been attributed to changes in lifestyle behaviors following immigration, but few studies have considered the psychosocial impact of immigration upon biomarkers of disease risk.

PURPOSE

To examine associations of psychological stress and social isolation with markers of type 2 diabetes risk over time among US Chinese immigrants.

METHODS

In this longitudinal study of 614 Chinese immigrants, participants completed assessments of perceived stress, acculturative stress, negative life events, and social isolation annually at three time points. Fasting blood samples were obtained at each time point to measure blood glucose, glycated hemoglobin, and insulin resistance. Mean duration between baseline and follow-up assessments was approximately 2 years.

RESULTS

Increases in migration-related stress, perceived stress and social isolation were associated with significant increases in fasting glucose at follow-up independent of age, body mass index, length of US residence, and other potential covariates. Moreover, increases in glucose varied depending on perceived stress levels at baseline, such that those with higher baseline stress had a steeper increase in glucose over time.

CONCLUSIONS

Psychological stress and social isolation are associated with increases in fasting glucose in a sample of US Chinese immigrants. Findings suggest that the unique experiences of immigration may be involved in the risk of developing type 2 diabetes, a condition that is prevalent among US Chinese despite relatively low rates of obesity.

A comprehensive review on fructosyl peptide oxidase as an important enzyme for present hemoglobin A1c assays

Glycated proteins are generated by binding of glucose to the proteins in blood stream through a nonenzymatic reaction. Hemoglobin A1c (HbA1c) is a glycated protein with glucose at the N-terminal of β-chain. HbA1c is extensively used as an indicator for assessing the blood glucose concentration in diabetes patients. There are different conventional clinical methods for the detection of HbA1c. However, enzymatic detection method has newly obtained great attention for its high precision and cost-effectiveness. Today, fructosyl peptide oxidase (FPOX) plays a key role in the enzymatic measurement of HbA1c, and different companies have marketed HbA1c assay systems based on FPOX. Recent investigations show that FPOX could be used in assaying HbA1 without requiring HbA1c primary digestion. It could also be applied as a biosensor for HbA1c detection. In this review, we have discussed the recent improvements of FPOX properties, different methods of FPOX purification, solubility, and immobilization, and also the use of FPOX in HbA1c biosensors.

Analytical performance evaluation of hemoglobin A1c on an ARKRAY HA-8160 analyzer with newly-developed mobile phase buffer

Background

Most glycated hemoglobin A1c (HbA1c) analytical reagents used were obtained from the analyzer's manufacturer. However, clinical laboratories need more choices for HbA1c analytical reagents to overcome the limitations of dedicated reagents for special analyzers. We developed new mobile phase buffers as HbA1c diagnostic reagents and evaluated their analytical performance for the HbA1c assay.

Methods

Different mobile phase buffers used as HbA1c diagnostic reagents were prepared using different concentrations of sodium salts. According to the Clinical and Laboratory Standards Institute (CLSI) recommendation guidelines, the analytical performances of the newly developed mobile phase buffers were evaluated on an ARKRAY HA-8160 Analyzer. Both quality controls and clinical blood samples were used in these experiments. To assess the quality of the newly developed mobile phase buffers, precision, accuracy, linearity, carryover, interference, bias, correlation with commercial reagents, and stability were analyzed.

Results

The CVs of intra-assay precision and interassay precision of quality control and clinical.There were fewer than 1.00 % blood sample assays using the newly developed mobile phase buffer. The RDs of accuracy were less than 1.00 %. Linearity: R2 = 0.9998 in the concentration range of 4.40%-17.30 %. Carryover: 0.00 %. Reagent comparison revealed that the Pearson regression equation was Y = 0.9884x+0.05692 (R2 = 0.9977), and the Bland-Altman mean difference was -0.02650 % (CI: -0.2121 %-0.1591 %) between the two analytical reagents. Stability was also acceptable within 12 months. This mobile phase buffer showed good anti-interference ability.

Conclusion

The newly developed mobile phase buffers demonstrated good analytical performance and were suitable for clinical HbA1c assays on an ARKRAY HA-8160 Analyzer.

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

1-Amino-1-deoxy-d-fructose (fructosamine, FN) derivatives are omnipresent in all living organisms, as a result of non-enzymatic condensation and Amadori rearrangement reactions between free glucose and biogenic amines such as amino acids, polypeptides, or aminophospholipids. Over decades, steady interest in fructosamine was largely sustained by its role as a key intermediate structure in the Maillard reaction that is responsible for the organoleptic and nutritional value of thermally processed foods, and for pathophysiological effects of hyperglycemia in diabetes. New trends in fructosamine research include the discovery and engineering of FN-processing enzymes, development of advanced tools for hyperglycemia monitoring, and evaluation of the therapeutic potential of both fructosamines and FN-recognizing proteins. This article covers developments in the field of fructosamine and its derivatives since 2010 and attempts to ascertain challenges in future research.

In silico characterization of fructosyl peptide oxidase properties from Eupenicillium terrenum

Fructosyl peptide oxidase (FPOX) enzyme from Eupenicillium terrenum has a high potential to be applied as a diagnostic enzyme. The aim of the present study is the characterization of FPOX from E. terrenum using different bioinformatics tools. The computational prediction of the RNA and protein secondary structures of FPOX, solubility profile in Escherichia coli, stability, domains, and functional properties were performed. In the FPOX protein, six motifs were detected. The d-amino acid oxidase motif was found as the most important motif that is a FAD-dependent oxidoreductase. The cysteines including 97, 154, 234, 280, and 360 showed a lower score than -10 that have a low possibility for participitation in the formation of the SS bond. The 56.52% of FPOX amino acids are nonpolar. Random coils are dominant in the FPOX sequence, followed by alpha-helix and extended strand. The fpox gene is capable of generating a stable RNA secondary structure (-423.90 kcal/mol) in E. coli. FPOX has a large number of hydrophobic amino acids. FPOX showed a low solubility in E. coli which has several aggregation-prone sites in its 3-D structure. According to the scores, the best mutation candidate for increasing solubility was the conversion of methionine 302 to arginine. The melting temperature of FPOX based on its amino acid sequence was 55°C to 65°C. The amounts of thermodynamic parameters for the FPOX enzyme were -137.4 kcal/mol, -3.59 kcal/(mol K), and -6.8 kcal/mol for standard folding enthalpy, heat capacity, and folding free energy, respectively. In conclusion, the in silico study of proteins can provide a valuable method for better understanding the protein properties and functions for use in our purposes.

HbA1c and biomarkers of diabetes mellitus in Clinical Chemistry and Laboratory Medicine: ten years after

Since its discovery in the late 1960s, HbA_1c has proven to be a major biomarker of diabetes mellitus survey and diagnosis. Other biomarkers have also been described using classical laboratory methods or more innovative, non-invasive ones. All biomarkers of diabetes, including the historical glucose assay, have well-controlled strengths and limitations, determining their indications in clinical use. They all request high quality preanalytical and analytical methodologies, necessitating a strict evaluation of their performances by external quality control assessment trials. Specific requirements are needed for point-of-care testing technologies. This general overview, which describes how old and new tools of diabetes mellitus biological survey have evolved over the last decade, has been built through the prism of papers published in Clinical Chemistry and Laboratory Medicine during this period.

A step towards optimal efficiency of HbA1c measurement as a first-line laboratory test: the TOP-HOLE (Towards OPtimal glycoHemOgLobin tEsting) project

OBJECTIVES

The TOP-HOLE (Towards OPtimal glycoHemOgLobin tEsting) project aimed to validate the HbA_1c enzymatic method on the Abbott Alinity c platform and to implement the HbA_1c testing process on the total laboratory automation (TLA) system of our institution.

METHODS

Three different measuring systems were employed: Architect c4000 stand-alone (s-a), Alinity c s-a, and Alinity c TLA. Eight frozen whole blood samples, IFCC value-assigned, were used for checking trueness. A comparison study testing transferability of HbA_1c results from Architect to Alinity was also performed. The alignment of Alinity TLA vs. s-a was verified and the measurement uncertainty (MU) estimated according to ISO 20914:2019. Turnaround time (TAT) and full time equivalent (FTE) were used as efficiency indicators.

RESULTS

For HbA_1c concentrations covering cut-offs adopted in clinical setting, the bias for both Architect and Alinity s-a was negligible. When compared with Architect, Alinity showed a mean positive bias of 0.54 mmol/mol, corresponding to a mean difference of 0.87%. A perfect alignment of Alinity TLA to the Alinity s-a was shown, and a MU of 1.58% was obtained, widely fulfilling the desirable 3.0% goal. After the full automation of HbA_1c testing, 90% of results were released with a maximum TAT of 1 h, 0.30 FTE resource was also saved.

CONCLUSIONS

The traceability of Alinity HbA_1c enzymatic assay to the IFCC reference system was correctly implemented. We successfully completed the integration of the HbA_1c testing on our TLA system, without worsening the optimal analytical performance. The shift of HbA_1c testing from s-a mode to TLA significantly decreased TAT.

Development of glycated peptide enzyme sensor based flow injection analysis system for haemoglobin A1c monitoring using quasi-direct electron transfer type engineered fructosyl peptide oxidase

Haemoglobin A1c (hemoglobin A1c, HbA1c) is an important long-term glycemic control marker for diabetes. The aim of this study was to develop an enzyme flow injection analysis (FIA) system using engineered fructosyl peptide oxidase (FPOx) based on 2.5th generation principle for an HbA1c automated analytical system. FPOx from Phaeosphaeria nodorum (PnFPOx) was engineered by introducing a Lys residue at the R414 position, to be modified with amine reactive phenazine ethosulfate (arPES) in proximity of FAD. The engineered PnFPOx mutant with minimized oxidase activity, N56A/R414K, showed quasi-direct electron transfer (quasi-DET) ability after PES-modification. The FIA system was constructed by employing a PES-modified PnFPOx N56A/R414K and operated at 0 V against Ag/AgCl. The system showed reproducible responses with a linear range of 20-500 μM for both fructosyl valine (FV) and fructosyl valylhistidine (FVH), with sensitivities of 0.49 nA μM^-1 and 0.13 nA μM^-1, and the detection limits of 1.3 μM and 2.0 μM for FV and FVH, respectively. These results indicate that the enzyme electrochemical FIA system covers the clinical range of HbA1c detection for more 200 consecutive measurements. Protease digested three different levels of HbA1c samples including healthy and diabetic range subjects were also measured with the FIA system. Thus, it will be possible to develop an integrated system consisting of sample pretreatment and sample electrochemical measurement based on an FIA system possessing quasi-DET type PnFPOx.

Gold Nanostar Colorimetric Detection of Fructosyl Valine as a Potential Future Point of Care Biosensor Candidate for Glycated Haemoglobin Detection

Diabetes Mellitus is a growing global concern. The current methods used to detect glycated haemoglobin are precise, however, utilise expensive equipment, reagents and consumables. These are luxuries which rural communities cannot access. The nanotechnology methods which have been developed for glycated haemoglobin detection are predominantly electrochemically based, have complicated lengthy fabrication processes and utilise toxic chemicals. Here a fructosyl amino acid oxidase gold nanostar biosensor has been developed as a potential future point of care biosensor candidate for glycated haemoglobin detection. The workup done on this biosensor showed that it was able to give a spectrophotometric readout and colorimetric result with naked eye detection in blank serum spiked with fructosyl valine.

Comparison of Enzymatic Assay for HBA1C Measurement (Abbott Architect) With Capillary Electrophoresis (Sebia Minicap Flex Piercing Analyser)

Objective

To compare the analytical performances of the enzymatic method (EM) and capillary electrophoresis (CE) for hemoglobin A1c (HbA1c) measurement.

Methods

Imprecision, carryover, stability, linearity, method comparison, and interferences were evaluated for HbA1c via EM (Abbott Laboratories, Inc) and CE (Sebia).

Results

Both methods have shown overall within-laboratory imprecision of less than 3% for International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) units (<2% National Glycohemoglobin Standardization Program [NGSP] units). Carryover effects were within acceptable criteria. The linearity of both methods has proven to be excellent (R2 = 0.999). Significant proportional and constant difference were found for EM, compared with CE, but were not clinically relevant (<5 mmol/mol; NGSP <0.5%). At the clinically relevant HbA1c concentration, stability observed with both methods was acceptable (bias, <3%). Triglyceride levels of 8.11 mmol per L or greater showed to interfere with EM and fetal hemoglobin (HbF) of 10.6% or greater with CE.

Conclusion

The enzymatic method proved to be comparable to the CE method in analytical performances; however, certain interferences can influence the measurements of each method.

Evaluating new HbA1c methods for adoption by the IFCC and NGSP reference networks using international quality targets

BACKGROUND

As a reference laboratory for HbA1c, it is essential to have accurate and precise HbA1c methods covering a range of measurement principles. We report an evaluation of the Abbott Enzymatic (Architect c4000), Roche Gen.3 HbA1c (Cobas c513) and Tosoh G11 using different quality targets.

METHODS

The effect of hemoglobin variants, other potential interferences and the performance in comparison to both the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and the National Glycohemoglobin Standardization Program (NGSP) reference systems was assessed using certified evaluation protocols.

RESULTS

Each of the evaluated HbA1c methods had CVs <3% in SI units and <2% in NGSP units at 46 mmol/mol (6.4%) and 72 mmol/mol (8.7%) and passed the NGSP criteria when compared with six secondary reference measurement procedures (SRMPs). Sigma was 8.6 for Abbott Enzymatic, 3.3 for Roche Cobas c513 and 6.9 for Tosoh G11. No clinically significant interference was detected for the common Hb variants for the three methods.

CONCLUSIONS

All three methods performed well and are suitable for clinical application in the analysis of HbA1c. Partly based on the result of this study, the Abbott Enzymatic method on the Architect c4000 and the Roche Gen.3 HbA1c on the Cobas c513 are now official, certified IFCC and NGSP SRMPs in the IFCC and NGSP networks. Sigma metrics quality criteria presented in a graph distinguish between good and excellent performance.

Capillarys 2 Flex Piercing: Analytical performance assessment according to CLSI protocols for HbA1c quantification

HbA_1c is used for monitoring diabetic balance. In this paper we report an assessment of the analytical performances of Capillarys 2 Flex Piercing (C2FP) for HbA_1c measurement using CE (Capillary Electrophoresis). CLSI (Clinical and Laboratory Standard Institute) protocols are used for the evaluation of apparatus performances: precision, linearity, method comparison, trueness and common interferences. HbA_1c CVs average in intra-assay was 1.6% between run imprecision CV ranged from 0.1 to 1.8%. The linearity was demonstrated between 4.7 and 15.0%. The comparison study revealed that Bland Altman plot mean difference was equal to -0.03 (CI 95% (-0.05 to -0.0003)) and Passing-Bablok regression intercept was -0.05, CI95%(-0.13 -  -0.05); slope: 1.00, CI95%[1.00-1.01]. A strong correlation (r > 0.99) was proved. No significant effects of hemoglobin variants were seen with CE on HbA_1c measurement. No problem related to sample-to-sample carry over was noted. No interferences of LA_1c and cHb were observed. CE allowed quantification of HbA_1c even at low level of total hemoglobin (40 g/L) in contrast to HPLC. Furthermore, this analyzer offered the opportunity of quantifying the HbA₂ simultaneously with HbA_1c . This evaluation showed that C2FP is a convenient system for the control of diabetes and the detection of hemoglobinopathies.

Standardising HbA1c-based diabetes diagnosis: opportunities and challenges

Globally, the incidence of diabetes mellitus is rising at an alarming rate and has become a health crisis that threatens the economies of all nations. Therefore, diagnosing diabetes has become an important issue in the management of diabetes. Glycated hemoglobin (HbA1c) is now recommended as a means to diagnose diabetes, but its use still has limitations. In this article, the biology, measurement, standardization, and opportunities and challenges of the use of HbA1c to diagnose diabetes are reviewed. More specifically, its use in China and the Asian region is discussed in detail.

Prevalence of hemoglobin variants in a diabetic population at high risk of hemoglobinopathies and optimization of HbA1c monitoring by incorporating HPLC in the laboratory workup

BACKGROUND

In Tunisia, diabetes mellitus and hemoglobinopathies are major public health problems. Glycated hemoglobin (HbA1c) is recommended for long-term monitoring of diabetes mellitus, but the presence of hemoglobin variants may interfere with HbA1c measurement. The aim was to determine the prevalence of hemoglobin variants in Tunisian diabetics and optimize the monitoring of diabetics using HbA1c.

METHODS

The study enrolled 9,792 Tunisian diabetic patients. HbA1c was measured by cation-exchange high-pressure liquid chromatography (HPLC). All the chromatograms were analyzed for the presence of Hb variants.

RESULTS

We identified 228 cases (2.33%) of Hb variants with D-10 HPLC (Bio-Rad): 191 with HbA/S trait, 27 with HbA/C trait, and 10 hemoglobin variants with the mention 'Variant-Window' on the chromatograms and subsequently identified as HbA/S on Variant I HPLC (Bio-Rad). Thus, the prevalence of HbS was 2.05%. We did not find any homozygous variant. All HbA1c results were reported to the treating physician.

CONCLUSIONS

To evaluate glycated hemoglobin in populations with a high prevalence of hemoglobinopathies, we should use the HPLC method, which is easy, economical, and reliable. Based on an algorithm, hemoglobin variants visualized on HPLC should be reported to the physician to improve the management of patients.