Effects of the Hb E, Hb H and Hb G-Taichung variants on HbA1c values by the Bio-Rad variant™ II turbo analyzer

Is it Time to Migrate to Liquid Chromatography Automated Platforms in the Clinical Laboratory? A Brief Point of View

Liquid chromatography coupled to mass spectrometry already started to surpass the major drawbacks in terms of sensitivity, specificity and cross-reactivity that some analytical methods used in the clinical laboratory exhibit. This hyphenated technique is already preferred for specific applications while finding its own place in the clinical laboratory setting. However, large-scale usage, high-throughput analysis and lack of automation emerge as shortcomings that liquid chromatography coupled to mass spectrometry still has to overrun in order to be used on a larger scale in the clinical laboratory. The aim of this review article is to point out the present-day position of the liquid chromatography coupled to mass spectrometry technique while trying to understand how this analytical method relates to the basic working framework of the clinical laboratory. This paper offers insights about the main regulation and traceability criteria that this coupling method has to align and comply to, automation and standardization issues and finally the critical steps in sample preparation workflows all related to the high-throughput analysis framework. Further steps are to be made toward automation, speed and easy-to-use concept; however, the current technological and quality premises are favorable for chromatographic coupled to mass spectral methods.

Associations between HbA1c-derived estimated average glucose and fasting plasma glucose in patients with normal and abnormal hemoglobin patterns

Fasting plasma glucose (FPG) and HbA1c are well-known tests for monitoring short and long-term glycemic control, respectively. Estimated average glucose (eAG) is derived from the HbA1c for expression in the same units as FPG. The present study aimed to evaluate the association between eAG and FPG values. This retrospective study was performed on 1285 patients who measured the FPG and HbA1c (capillary electrophoresis method) values on the same day. They were initially divided into 3 hemoglobin-pattern groups, normal, HbE, and high HbA₂, and then these 3 groups were further subdivided into whole group, subgroup 1 (HbA1c ≤ 7%) and subgroup 2 (HbA1c >7%) for analytical comparisons. The eAG values were calculated using Nathan's equation. The differences, agreements, and correlations between eAG and FPG were evaluated. Good agreements and strong positive correlations between eAG and FPG values were observed in all 3 whole groups. In subgroup analysis, the degrees of agreement and correlation depended on the level of glycemic control, as all associations became stronger with better glycemic control. Additionally, the HbA1c levels and different eAG-FPG values between the normal and other groups were not significantly different in either whole group or subgroup comparisons. Our study found good agreements and strong positive correlations between eAG and FPG in all groups, indicating that high HbA₂ or HbE did not affect the HbA1c levels or thus the associations between eAG and FPG. Reporting the eAG together with the HbA1c value should help improve the understanding of glycemic status in patients, leading to improved blood glucose control.

Characterization of glycated hemoglobin based on Raman spectroscopy and artificial neural networks

The World Health Organization has declared the glycated hemoglobin (HbA1c) as a gold standard biomarker for diabetes diagnosis; this has led to relevant research on the spectral behavior and characterization of HbA1c. This paper presents an analysis of Raman peaks of commercial lyophilized HbA1c, diluted in distilled water, using concentrations of 4.76% and 9.09%, as well as pure powder (100% concentration). Vibrational Raman peak positions of HbA1c powder were found at 1578, 1571, 1536, 1436, 1311, 1308, 1230, 1222, 1114, 1106, 969, 799 and 665 cm^-1; these values are consistent with results reported in other works. Besides, a nonlinear regression model based on a Feed-Forward Neural Network (FFNN) was built to quantify percentages of HbA1c for unknown concentrations. Using the Raman spectra as independent variables, the regression provided a Root Mean Square Error in Cross-Validation (RMSECV) of 0.08% ± 0.04. We also include a detailed molecular assignment of the average spectra of lyophilized powder of HbA1c.

HbA1C as a marker of retrograde glycaemic control in diabetes patient with co-existed beta-thalassaemia: A case report and a literature review

WHAT IS KNOWN AND OBJECTIVE

The HbA1C marker used in assessing diabetes control quality is not sufficient in diabetes patients with thalassaemia.

CASE DESCRIPTION

A male diabetic patient with thalassaemia was hospitalized due to distal neuropathic pain, right toe trophic ulcer, unacceptable five-point glycaemic profile and recommended HbA1C value. After simultaneously initiated insulin therapy and management of ulcer by hyperbaric oxygen, the patient showed improved glycaemic control and ulcer healing, which led to the patient's discharge.

WHAT IS NEW AND CONCLUSION

In thalassaemia and haemoglobinopathies, due to discrepancies in the five-point glycaemic profile and HbA1C values, it is necessary to measure HbA1C with a different method or to determine HbA1C and fructosamine simultaneously.

False measurement of glycated hemoglobin in patients without hemoglobin A

Background: Hemoglobin (Hb) A1c, a biochemical marker widely used in monitoring diabetes mellitus, can be quantitatively measured by various examining systems. However, significant errors still exist. In the present study, we evaluated the HbA1c level in five patients with compound heterozygotes by five different examining systems and our goal is to identify the existence of erroneous HbA1c measurement.Methods: Blood samples collected from normal (no hemoglobin variants) and abnormal (compound heterozygotes) patients were analyzed by capillary electrophoresis technique and sequence analysis. The samples without HbA expression via above methods were further analyzed for HbA1c by ion exchange HPLC Variant II/ Variant II Turbo 2.0 (VII and VII-T 2.0), boronate affinity HPLC, capillary electrophoresis, and Tinaquant immunoassay.Results: HbA1c expression were unexpectedly detected in the compound heterozygous samples by using additional examining systems: The HPLC VII and VII-T 2.0 detected HbA1c expression in two of five samples and failed to detect the abnormal HbA2 expression; the CE system detected HbA1c expression in one of five samples with abnormal HbA2 expression; the Ultra2 and PPI system detected the HbA1c expression of all samples without abnormal HbA2Conclusions: Five human samples without HbA expression were additionally detected with HbA1c expression with or without abnormal HbA2 expression by five analysis systems and the different examining assay potentially affected the test results. These results demonstrated that the limitations of current examining systems for monitoring patients with hemoglobin disorders highlighting the further improvement in the method of clinical HbA examination.

Different strategies for detection of HbA1c emphasizing on biosensors and point-of-care analyzers

Measurement of glycosylated hemoglobin (HbA1c) is a gold standard procedure for assessing long term glycemic control in individuals with diabetes mellitus as it gives the stable and reliable value of blood glucose levels for a period of 90-120 days. HbA1c is formed by the non-enzymatic glycation of terminal valine of hemoglobin. The analysis of HbA1c tends to be complicated because there are more than 300 different assay methods for measuring HbA1c which leads to variations in reported values from same samples. Therefore, standardization of detection methods is recommended. The review outlines the current research activities on developing assays including biosensors for the detection of HbA1c. The pros and cons of different techniques for measuring HbA1c are outlined. The performance of current point-of-care HbA1c analyzers available on the market are also compared and discussed. The future perspectives for HbA1c detection and diabetes management are proposed.

Measurement of HbA1c and HbA2 by Capillarys 2 Flex Piercing HbA1c programme for simultaneous management of diabetes and screening for thalassemia

Introduction

Thalassemia could interfere with some assays for haemoglobin A_1c (HbA_1c) measurement, therefore, it is useful to be able to screen for thalassemia while measuring HbA_1c. We used Capillarys 2 Flex Piercing (Capillarys 2FP) HbA_1c programme to simultaneously measure HbA_1c and screen for thalassemia.

Materials and methods

Samples from 498 normal controls and 175 thalassemia patients were analysed by Capillarys 2FP HbA_1c programme (Sebia, France). For method comparison, HbA_1c was quantified by Premier Hb9210 (Trinity Biotech, Ireland) in 98 thalassaemia patients samples. For verification, HbA_1c from eight thalassaemia patients was confirmed by IFCC reference method.

Results

Among 98 thalassaemia samples, Capillarys 2FP did not provide an HbA_1c result in three samples with HbH due to the overlapping of HbBart’s with HbA_1c fraction; for the remaining 95 thalassaemia samples, Bland-Altman plot showed 0.00 ± 0.35% absolute bias between two systems, and a significant positive bias above 7% was observed only in two HbH samples. The HbA_1c values obtained by Capillarys 2FP were consistent with the IFCC targets (relative bias below ± 6%) in all of the eight samples tested by both methods. For screening samples with alpha (α-) thalassaemia silent/trait or beta (β-) thalassemia trait, the optimal HbA₂ cut-off values were ≤ 2.2% and > 2.8%, respectively.

Conclusions

Our results demonstrated the Capillarys 2FP HbA_1c system could report an accurate HbA_1c value in thalassemia silent/trait, and HbA₂ value (≤ 2.2% for α-thalassaemia silent/trait and > 2.8% for β-thalassemia trait) and abnormal bands (HbH and/or HbBart’s for HbH disease, HbF for β-thalassemia) may provide valuable information for screening.

Hb variants in Korea: effect on HbA1c using five routine methods

BACKGROUND

Quantification of glycated hemoglobin (HbA1c) is a challenge in patients with hemoglobin (Hb) variants. We evaluated the impact of various Hb variants on five routine HbA1c assays by comparing with the IFCC reference measurement procedure (RMP).

METHODS

Whole blood samples showing warning flags or no results on routine HPLC HbA1c assays were confirmed for Hb variants and were submitted to HbA1c quantification using Sebia Capillarys 2 Flex Piercing, Roche Tina-quant HbA1c Gen. 2, Bio-Rad Variant II Turbo 2.0, ADAMS HA-8180, Tosoh G8 standard mode, and IFCC RMP using LC-MS.

RESULTS

Among 114 samples, the most common variants were Hb G-Coushatta (n=47), Queens (n=41), Ube-4 (n=11), Chad (n=4), Yamagata (n=4), G-His-Tsou (n=2), G-Taipei (n=1), Fort de France (n=1), Hoshida (n=1), and two novel variants (Hb α-globin, HBA 52 Gly>Cys and Hb β-globin, HBB 146 His>Asn). In terms of control samples, all the result of HbA1c were "acceptable", within the criteria of ±7% compared to IFCC RMP target values. However, percentage of "unacceptable" results of samples with Hb variants were 16% for Capillarys 2, 7% for Tina-quant, 51% for Variant II Turbo 2.0, 95% for G8 standard mode, and 89% for HA-8180. The Capillarys 2 and HA-8180 assay did not provide the results in 5 and 40 samples with Hb variants, respectively.

CONCLUSIONS

HbA1c results from five routine assays in patients with relatively common Hb variants in Korea showed various degrees of bias compared to those of IFCC RMP. Therefore, laboratories should be aware of the limitation of their methods with respect to interference from Hb variants found commonly in their local population and suggest an alternative HbA1c quantification method.

Interference of common haemoglobin variants with the Tosoh G7 standard mode HbA1c method

BACKGROUND

HbA1c methods may be prone to interference by the presence of haemoglobin variants. In contrast to the variant mode of the HbA1c method on the Tosoh G7 instrument, the literature lacks investigations of haemoglobin variant interference with the standard mode. The current study sought to investigate whether different haemoglobin variants interfere with the Tosoh G7 standard mode HbA1c method, and whether present haemoglobin variants are identifiable on respective chromatograms.

METHODS

Samples routinely analyzed for HbA1c and suspected of having haemoglobin variants (N = 103) were included. HbA1c was measured on a Tosoh G7 in standard mode (Tosoh Corporation, Japan), and on the DCA Vantage (Siemens, Germany). Haemoglobin variants were identified using the VARIANT(™)β-Thalassemia Short Program (Bio-Rad Laboratories, Hercules, CA, USA) and by DNA sequencing.

RESULTS

The Tosoh G7 in standard mode measured significantly lower HbA1c results (between 1.0 and 2.5 percentage points absolute bias corresponding to between 11 and 27 mmol/mol, p < 0.001) in samples in which common haemoglobin variants (HbS, HbC, HbD or HbE) were present (n = 61). No significant difference in HbA1c (0.04 percentage points, p = 0.74) was found between Tosoh G7 standard mode and DCA Vantage in samples in which haemoglobin variants were absent (n = 36). In contrast to HbS and HbD, HbE and HbC trait could be identified on respective chromatograms.

CONCLUSION

The presence of common haemoglobin variants results in falsely low HbA1c measurements on the Tosoh G7 in standard mode. HbS and HbD trait are not identifiable on respective haemoglobin chromatograms.

Recent Progress in Electrochemical HbA1c Sensors: A Review

This article reviews recent progress made in the development of electrochemical glycated hemoglobin (HbA1c) sensors for the diagnosis and management of diabetes mellitus. Electrochemical HbA1c sensors are divided into two categories based on the detection protocol of the sensors. The first type of sensor directly detects HbA1c by binding HbA1c on the surface of an electrode through bio-affinity of antibody and boronic acids, followed by an appropriate mode of signal transduction. In the second type of sensor, HbA1c is indirectly determined by detecting a digestion product of HbA1c, fructosyl valine (FV). Thus, the former sensors rely on the selective binding of HbA1c to the surface of the electrodes followed by electrochemical signaling in amperometric, voltammetric, impedometric, or potentiometric mode. Redox active markers, such as ferrocene derivatives and ferricyanide/ferrocyanide ions, are often used for electrochemical signaling. For the latter sensors, HbA1c must be digested in advance by proteolytic enzymes to produce the FV fragment. FV is electrochemically detected through catalytic oxidation by fructosyl amine oxidase or by selective binding to imprinted polymers. The performance characteristics of HbA1c sensors are discussed in relation to their use in the diagnosis and control of diabetic mellitus.

The interference by HbF on HbA1c (BM Test HbA1c) measurement in enzymatic method

BACKGROUND

High performance liquid chromatography and immunological and enzymatic methods are known as the methods for HbA1c measurement. However, the differences in the principles of the methods may cause slight discrepancies, which become problems especially in the regions where hemoglobinopathies that have high HbF concentrations are commonly seen. In this report, we discuss the effect of HbF on the HbA1c measurement by the enzymatic method (BM Test HbA1c) which can be applied to automatic analyzer of high sample throughput.

METHODS

Thirty-five samples (HbF concentration: between 1.4 and 90.1%) and 68 samples (HbF concentration: <1.0%) were analyzed by high performance liquid chromatography (Tosoh G8) and BM Test HbA1c. The results by BM Test HbA1c were compared with those by the high performance liquid chromatography and International Federation of Clinical Chemistry reference method.

RESULTS

The high and positive correlation coefficient was demonstrated between the enzymatic and International Federation of Clinical Chemistry methods for the samples with normal HbF concentration. The samples with high HbF concentration exhibited high and positive correlation coefficient, although the figure is lower than that of the normal HbF concentration group.

CONCLUSIONS

BM Test HbA1c revealed a high and positive correlation with high performance liquid chromatography and International Federation of Clinical Chemistry reference methods. However, the HbA1c values by BM Test HbA1c and high performance liquid chromatography method were lower than those by International Federation of Clinical Chemistry reference method when the HbF concentration was high. BM Test HbA1c had some deviation from the International Federation of Clinical Chemistry reference method, while no significant interference was seen when the HbF values were less than 15%. When HbF is higher than 15%, however, the interpretation of HbA1c by BM Test may require some special consideration.

A rare haemoglobin variant (Hb Phnom Penh) manifesting as a falsely high haemoglobin A1c value on ion-exchange chromatography

Most haemoglobin (Hb) variants are clinically silent. However, some Hb variants may interfere with the measurement of haemoglobin A1c (HbA1c), resulting in spurious values depending on the assays used. We herein report the case of a 53-year-old Taiwanese man with type 2 diabetes mellitus, who presented with an abnormal HbA1c peak on ion-exchange chromatography. Additional investigations, including intensified self-monitored blood glucose tests, an alternative HbA1c assay, and a glycaemic indicator based on a different method, revealed that the HbA1c values were falsely elevated. Subsequent DNA analysis confirmed that the patient was heterozygous for the insertion of an isoleucine residue at codons 117/118 of the a1-globin gene, Hb Phnom Penh. Clinical laboratorians should be aware of the interfering factors in their HbA1c analysis. Cautious inspection of the chromatogram may provide a valuable clue to the presence of an Hb variant.

Hb H Interference on Measurement Of HbA1c With Ion-Exchange HPLC

In this article, an interference caused by hemoglobin H (Hb H), during the measurement of hemoglobin A1c (HbA1c) with ion exchange high pressure liquid chromatography (HPLC) method, was presented in blood sample of a 20-year-old male patient. HbA1c measurement was performed with Agilent 1200 HPLC system using a commercial Recipe HbA1c ion-exchange column. Hemoglobin electrophoresis was performed with Interlab G26 agarose electrophoresis automated compact system. HbA1c level was 18.2% and HbA0 level was 81.5% with ion-exchange HPLC method. Patient’s fasting serum glucose was assessed before HbA1c measurement and the result was 165 mg/dL (9.16 mmol/L). On the other hand, the result of HbA0 was 87.9%, Hb H was 10.8% and Hb A2 was 1.3% with electrophoresis. Whole blood test values were within reference ranges except MCV. MCV value was 79.6 fL. It is important to keep in mind that HbA1c level might be considered falsely high with ion-exchange HPLC method because of Hb H containing sample.

A rare hemoglobin variant (Hb Iraq-Halabja) causing spuriously low hemoglobin A1c values

Various laboratory and patient-related factors can affect the measurement of hemoglobin A1c (HbA1c). We herein present the case of a diabetic patient with spuriously low HbA1c values on ion-exchange high-performance liquid chromatography (HPLC). Further investigations revealed that the patient was heterozygous for a rare Hb variant, namely Hb Iraq-Halabja (β10 Ala→Val). This is the second report of this variant published in the literature. Clinicians should be aware of the limitations of HbA1c assays because inaccurate values may lead to the inappropriate management of diabetes. Unusual or discrepant HbA1c test results should prompt further investigations for potentially interfering factors, including rare Hb variants.

Pharmaceutical and biomedical applications of affinity chromatography: recent trends and developments

Affinity chromatography is a separation technique that has become increasingly important in work with biological samples and pharmaceutical agents. This method is based on the use of a biologically related agent as a stationary phase to selectively retain analytes or to study biological interactions. This review discusses the basic principles behind affinity chromatography and examines recent developments that have occurred in the use of this method for biomedical and pharmaceutical analysis. Techniques based on traditional affinity supports are discussed, but an emphasis is placed on methods in which affinity columns are used as part of HPLC systems or in combination with other analytical methods. General formats for affinity chromatography that are considered include step elution schemes, weak affinity chromatography, affinity extraction and affinity depletion. Specific separation techniques that are examined include lectin affinity chromatography, boronate affinity chromatography, immunoaffinity chromatography, and immobilized metal ion affinity chromatography. Approaches for the study of biological interactions by affinity chromatography are also presented, such as the measurement of equilibrium constants, rate constants, or competition and displacement effects. In addition, related developments in the use of immobilized enzyme reactors, molecularly imprinted polymers, dye ligands and aptamers are briefly considered.