Effects of hemoglobin C, D, E and S traits on measurements of hemoglobin A1c by twelve methods

Presumptive Identification of Clinically Significant Hemoglobin Variants Hb E, Hb S, Hb D in Hb A1c Capillary Electrophoresis

BACKGROUND

The quantitation of glycated hemoglobin (Hb A1c) represents an average blood glucose level for a period of 2 to 3 months for diagnosing, monitoring, and managing diabetes mellitus. Unreliable results are reported when hemoglobin (Hb) variants are present in the sample. Patients are advised to use an alternate method due to the presence of the variant Hb and a reflex test to Hb electrophoresis to obtain precise information about the Hb variant. The present study utilizes x axis values from Hb A1c capillary electrophoresis (CE) to identify clinically significant Hb variants Hb E, S, and D.

METHODS

Patient samples (n = 60) that showed a variant peak in the Hb A1c test with an x axis value of 190 to 240 were selected for the study. The migration position of the Hb variant (x axis value) and variant percent of the Hb A1c test were compared with the x axis value and variant percent in the Hb electrophoresis test to presumptively identify the variants. The identity of the variants was confirmed using mass spectrometry (MS).

RESULTS

Out of 60 samples, 20 samples were identified as Hb E (x axis 225-227), 20 samples were identified as Hb S (x axis 210-214), and 18 samples were identified as Hb D-Punjab (x axis 200-201). Two variants with an x axis value of 194 were identified as an α variant Hb Q India using MS. There is an overall negative shift of the x axis (-1 to -13 units) and a lower variant percent (-0.2% to -8.7%) in Hb A1c CE when compared with Hb electrophoresis.

CONCLUSIONS

The present study highlights the significance of the x axis value and variant percent to identify clinically significant Hb variants in the Hb A1c CE test.

Interference of hemoglobin variants with HbA1c measurements: comparison of 6 commonly used HbA1c methods with the IFCC reference method

BACKGROUND

Glycated hemoglobin, or hemoglobin A1c (HbA1c), serves as a crucial marker for diagnosing diabetes and monitoring its progression. We aimed to assess the interference posed by common Hb variants on popular HbA1c measurement systems.

METHODS

A total of 63 variant and nonvariant samples with target values assigned by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference method were included. We assessed 6 methods for measuring HbA1c in the presence of HbS, HbC, HbD, HbE, and fetal hemoglobin (HbF): 2 cation-exchange high-performance liquid chromatography (HPLC) methods (Bio-Rad D-100 and HLC-723 G8), a capillary electrophoresis (CE) method (Sebia Capillarys 3 TERA), an immunoassay (Roche c501), an enzyme assay system (Mindray BS-600M), and a boronate affinity method (Primus Premier Hb9210).

RESULTS

The HbA1c results for nonvariant samples from the 6 methods were in good agreement with the IFCC reference method results. The Bio-Rad D-100, Capillarys 3, Mindray BS-600M, Premier Hb9210, and Roche c501 showed no interference from HbS, HbC, HbD, and HbE. Clinically significant interference was observed for the HLC-723 G8 standard mode. Elevated HbF levels caused significant negative biases for all 6 methods, which increased with increasing HbF concentration.

CONCLUSION

Elevated levels of HbF can severely affect HbA1c measurements by borate affinity, immunoassays, and enzyme assays.

Innovations in HbA1c analysis: finding the balance between speed and accuracy. An investigation of a potential new Secondary Reference Measurement Procedure for the IFCC

OBJECTIVES

The escalating prevalence of diabetes worldwide has resulted in a dramatic increase in the number of people who need testing, which in turn necessitates faster HbA1c measurement. The Tosoh GR01 addresses the need for fast turnaround times of whilst offering pragmatic steps to maintain result accuracy in a single instrument by offering two distinct operating modes: Short Mode (SM) and Long Mode (LM). The aim of this study was to evaluate all relevant aspects of the performance of the Tosoh GR01 with a view to accepting the instrument as a future Secondary Reference Measurement Procedure (SRMP) for the IFCC.

METHODS

Certified Clinical & Laboratory Standards Institute (CLSI) Evaluation Protocols (EP) were used to evaluate precision (EP-5), accuracy (EP-9), linearity (EP-6), carry-over (EP-10) and the effect of hemoglobin variants and other potential interferences.

RESULTS

Both modes demonstrated CVs <0.6 % in SI units and <0.4 % in NGSP units at 46 mmol/mol (6.4 %) and 75 mmol/mol (9.0 %) and passed both National Glycohemoglobin Standardization Program (NGSP) and International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) certification procedures when compared with 7 IFCC Certified Secondary Reference Measurement Procedures (SRMP). Sigma for both modes was >6 when using the results of EP-5 and EP-9 at an HbA1c concentration of 50 mmol/mol (6.7 %). Neither mode showed any interference with common Hb-variants except for HbAE when HbA1c was >65 mmol/mol. In the SM HbAS, HbAD and HbAC were recognized but no result was reported.

CONCLUSIONS

There is a good balance between speed and accuracy for determining HbA1c with the Tosoh GR01 in both analytical modes and the device is suitable for use as an IFCC SRMP.

Evaluation of the Premier Hb9210 instrument for HbA1c determination

Background: Glycated hemoglobin measurements are a valuable tool for long-term blood glucose monitoring and the diagnosis of diabetes. Its widespread use has been made possible due to the development of new analytical methods with improved performances and standardization with reference materials. The aim of the present study was to evaluate the Trinity Biotech Premier Hb9210 analyzer for the measurement of HbA1c.Methods: The precision was assessed using the CLSI EP-15A3 and EP-10A3 protocols. The latter was also used to investigate linearity, carryover, and linear drift. The comparison study was performed between Premier Hb910 and Tosoh HLC-723 G8 through Passing-Bablok regression and the Bland-Altman plot. The Fleiss Kappa index was used to assess the degree of agreement. The interference of Hb variants was investigated using samples with Hb variants S, C, D, E, J, and Seville.Results: Within-run and between-run imprecision fell between 0.37% and 1.16%. No statistically significant nonlinearity, carry-over, and/or drift were observed. The resulting regression line of the Passing-Bablok analysis was y = 0.00 + 1.00x. The Pearson correlation coefficient was 0.997. In the Bland-Altman plot, the relative bias was 0.01%. The overall Fleiss Kappa index was 0.9. No interference from hemoglobin variants was observed.Conclusion: The Premier Hb9210 demonstrated a high degree of automation, reproducibility, good agreement, minimal carry-over effect, and excellent linearity across the wide range of HbA1c levels commonly found in diabetic patients and was not influenced by Hb variants.

Michaelis-Menten kinetic modeling of hemoglobin A1c status facilitates personalized glycemic control

INTRODUCTION

Discrepancy between measured HbA1c and HbA1c calculated from plasma glucose is associated with higher risk for diabetic complications. However, quantification of this difference is inaccurate due to the imperfect linear conversion models. We propose to introduce a mathematical formula that correlates with the observational data and supports individualized glycemic control.

METHODS

We analysed 175,437 simultaneous plasma glucose and HbA1c records stored in our laboratory database. Employing the Michaelis-Menten (MM) equation, we compared the calculated HbA1c levels to the measured HbA1c levels. Data from patients with multiple records were used to establish the patients' glycemic status and to assess the predictive power of our MM model.

RESULTS

HbA1c levels calculated with the MM equation closely matched the population's average HbA1c levels. The Michaelis constant (Km) had a negative correlation with HbA1c (r2 = 0.403). Using personalized Km values in the MM equation, 85.1% of HbA1c predictions were within 20% error (ADAG calculation: 78.4%). MM prediction also performed better in predicting pathologic HbA1c levels (0.904 AUC vs. 0.849 AUC for ADAG).

CONCLUSION

MM equation is an improvement over linear models and could be readily employed in routine diabetes management. Km is a reliable and quantifiable marker to characterize variations in glucose tolerance.

[Hemoglobin C Variant Affecting Glycated Hemoglobin Test Results: A Rare Case Report]

Hemoglobin (Hb) variants are common factors that affect the results of glycosylated hemoglobin (A1C) tests. Hemoglobin variants react differently to different testing methods. Herein, we presented the first ever report of the effect of hemoglobin C (Hb C) on the test results of A1C in the Chinese population. High performance liquid chromatography (HPLC) and capillary electrophoresis were performed to measure A1C. Hemoglobin electrophoresis was conducted to identify the hemoglobin variants. Hb sequencing was performed to determine the mutation sites on the β chain. HPLC showed decreased A1C results, which could be corrected by electrophoresis, but the electrophoresis graph still showed abnormal peaks. The hemoglobin electrophoresis results suggested that there were hemoglobin variants, which hemoglobin sequencing results revealed to be Hb C. Uncommon variations in a specific population tend to be overlooked. To avoid clinical decision-making being affected by the results of a single test, we recommend that an explanatory reporting model be routinely adopted for A1C tests so that all reports always contain explanatory notes for the testing methodology and analysis of the graphs.

Evaluation of local hemoglobinopathy prevalence and promotion of accurate hemoglobin A1c testing using historical data retrieval

OBJECTIVES

Heterozygous hemoglobin variants are known to cause method- and variant-specific interference with hemoglobin A1c (HbA1c) quantitation. Less attention has been paid to the role of other hemoglobin variants in confounding HbA1c testing. Here we evaluated the frequency with which enzymatic (ENZ) and immunoassay (IA) HbA1c quantitation methods, i.e., those unable to routinely detect the presence of hemoglobin variants, were used within our healthcare system for HbA1c analysis in patients with elevated fetal hemoglobin as well as compound heterozygous and homozygous variants.

DESIGN & METHODS

This analysis was enabled by automated review of HbA1c result history, implemented to promote detection of variants prior to HbA1c result reporting.

RESULTS

During a 54-week period, 319,290 HbA1c analyses were performed. We observed 110 unique patient cases (0.03% problem identification rate) in which HbA1c testing was ordered in the presence of either a homozygous or compound heterozygous hemoglobin variant or elevated hemoglobin F beyond the tolerance of the method. Among the 110 cases identified, 55 (50%) showed a compound heterozygous or homozygous hemoglobin variant while 55 (50%) showed elevated hemoglobin F. Of those cases involving a compound heterozygous or homozygous variant, 8/55 (15%) involved patients who had one or more ENZ or IA HbA1c results reported previously within our system. Of the 55 total compound heterozygous or homozygous variants identified, 37 (67%) were hemoglobin E, 10 (18%) hemoglobin S/C, 4 (7%) hemoglobin S, 2 (4%) hemoglobin C, 1 (2%) hemoglobin Camden, and 1 (2%) unidentified variant.

CONCLUSIONS

Exclusive use of methods unable to routinely detect the presence of hemoglobin variants may lead to reporting of HbA1c results that are not clinically meaningful.

Characterization of Samples with Minor P3 Peak Elevations in a High Pressure Liquid Chromatography System for HbA1c: Contributions of Hemoglobin Variants and Storage Conditions

BACKGROUND

In the Bio-Rad D-100TM (Bio-Rad, Hercules, CA) HPLC system for hemoglobin A1c (HbA1c) measurement, 7 peaks elute: HbA1a, HbA1b, HbF, LA1c, HbA1c, P3, and HbA0. HbA1c is calculated from the ratio of the HbA1c peak area to the total area, excluding HbF and peaks after HbA0, if present. A P3 peak >10% flags for potential interferences.

METHODS

We investigated 26 samples with elevated P3 peaks to determine the presence of hemoglobin variants, the effect of prolonged specimen storage in the P3 peak. The relationship between the P3 peak and the HbA1c concentration were also investigated.

RESULTS

No hemoglobin variants were identified when the P3 peak was <14% (n = 14). Hemoglobin variants were detected in 7 of 12 with a P3 peak between 17.0% and 28.2%. Sample storage at room temperature had minimum impact on the P3 peak area (n = 20); the average P3 bias was -0.5 (-8.1% bias) after 3 days and 0.6 (12.2% bias) after 5 days. P3 increased with increasing HbA1c concentrations in samples with P3 < 10%. Most samples with P3 above 10 and up to 14% had marked HbA1c elevations.

CONCLUSIONS

Minor elevations of the P3 peak were due only in part to hemoglobin variants, particularly in samples with P3 above 17% (below 28.2%). These elevations caused a decrease in HbA1c, whether hemoglobin variants are detected or not. Prolonged storage at room temperature did not cause P3 peaks to increase above 10%.

Evaluation of interference from 16 hemoglobin variants on hemoglobin A1c measurement by five methods

Hb variants prevalent in China are different from those in other countries. We aimed to assess the interference from Hb variants found in China on HbA1c measurement. All Hb variants were confirmed using Sanger sequencing. HbA1c was measured using a capillary electrophoresis method (Capillarys 3 OCTA), two cation-exchange high-performance liquid chromatography methods (ADAMS HA-8180V and HLC-723 G8 standard mode), an immunoassay (Cobas c501), and a boronate affinity chromatography method (Premier Hb9210). Premier Hb9210 was used as a comparative method. A total of 16 species of Hb variants were identified in 102 variant carriers. The most common variant was Hb E, followed by Hb Q-Thailand, Hb New York and Hb J-Bangkok. Clinically significant interference was observed for the Capillarys 3 OCTA (two Hb variants), ADAMS HA-8180V (seven Hb variants), HLC-723 G8 (14 Hb variants), and Cobas c501 (two Hb variants). The proportion of unacceptable HbA1c results was 13.7% for Capillarys 3 OCTA, 52.9% for HA-8180V, 83.3% for HLC-723 G8, and 3.9% for Cobas c501. Hb variants in China severely affect the accuracy of some commonly used HbA1c methods.

Identification of Hemoglobin Variants Prevalent in China and Their Effects on Hemoglobin A1c Measurements

OBJECTIVES

We aimed to evaluate the effects of hemoglobin (Hb) variants prevalent in China on HbA1c measurements and to identify them during HbA1c measurements.

METHODS

We evaluated a cation-exchange high-performance liquid chromatography (HPLC) method (Bio-Rad D-100), a capillary electrophoresis (CE) method (Capillarys 3 TERA), an immunoassay (Cobas c501), and a boronate affinity method (Premier Hb9210, as a comparative method) for HbA1c measurements in the presence of Hb variants prevalent in China.

RESULTS

The Bio-Rad D-100 and Capillarys 3 TERA gave specific retention times and numeric migration positions for each Hb variant, respectively, showing excellent interindividual reproducibility. All methods showed statistically significant differences (P < .01) for several variants. Clinically significant effects were observed for the Bio-Rad D-100 (Hb New York and Hb J-Bangkok), Capillarys 3 TERA (Hb New York and Hb J-Bangkok), and Cobas c501 (Hb New York). Among 297 samples with Hb variants, there were 75 (25.3%) unacceptable results for Bio-Rad D-100, 28 (9.4%) for Capillarys 3 TERA, and 19 (6.4%) for Cobas c501 compared with the results from Premier Hb9210.

CONCLUSIONS

Some Hb variants prevalent in China affect HbA1c measurements. The HPLC retention time and CE migration position can aid in the presumptive identification of Hb variants.

Hemoglobin Wayne causing a falsely elevated hemoglobin A1c

Hemoglobin A1c (HbA1c) is an important tool for diagnosis and management of patients with diabetes mellitus (DM). However, hemoglobin variants can interfere with laboratory assays and lead to inaccurate results. This study describes a patient who was found to have falsely elevated HbA1c values secondary to hemoglobin Wayne, a rare hemoglobin variant. Although hemoglobin Wayne is often clinically silent, falsely elevated HbA1c results could lead to unnecessary medical interventions that could cause patient harm. This variation in results highlights the importance of utilizing additional measurements such as glucose readings and evaluating for hemoglobin variants when results are discordant.

Evaluation of interference from hemoglobin C, D, E and S traits on measurements of hemoglobin A1c by fifteen methods

BACKGROUND

Hemoglobin C, D Punjab, E or S trait can interfere with hemoglobin A1c (HbA1c) results. We assessed whether they affect results obtained with 15 current assay methods.

METHODS

Hemoglobin AA (HbAA), HbAC, HbAD Punjab, HbAE and HbAS samples were analyzed on 2 enzymatic, 4 ion-exchange HPLC and 9 immunoassay methods. Trinity Premier Hb9210 boronate affinity HPLC was the comparative method. An overall test of coincidence of least-squared linear regression lines was performed to determine if HbA1c results were statistically significantly different from those of HbAA samples. Clinically significant interference was defined as >6% difference from HbAA at 6 or 9% HbA1c compared to Premier Hb9210 using Deming regression.

RESULTS

All methods showed statistically significant effects for one or more variants. Clinically significant effects were observed for the Tosoh G11 variant mode (HbAD), Roche b 101 (HbAC and HbAE) and Siemens DCA Vantage (HbAE and HbAS). All other methods (Beckman Coulter B93009 and B00389 on DxC700AU, and Unicel DxC, Ortho Clinical Vitros 5.1, Roche cobas c 513, Siemens Dimension RxL and Vista, and Enzymatic on Advia and Atellica, Tosoh G8 5.24 and 5.28, and GX) showed no clinically significant differences.

CONCLUSIONS

A few methods showed interference from one or more variants. Laboratories need to be aware of potential HbA1c assay interferences.

Evaluation of an Ion-Exchange HPLC Device for HbA1c Measurement

BACKGROUND

The ADAMS™ HA-8180V is the 8th generation of a fully automated ion-exchange HPLC system from ARKRAY, and the first to be released onto the US market. We evaluated the HA-8180V, for routine hemoglobin A1c measurement in comparison with the Roche Cobas c501, the Tosoh G8 analyzer for normal hemoglobin, and with the Trinity analyzer for hemoglobin variants.

METHODS

The analytical performance (linearity, precision, carryover, and sample stability) was assessed based on the Clinical and Laboratory Standards Institute (CLSI) and manufacturer guidelines. A comparison of the HA-8180V against two major analytical methods was performed for 100 whole blood samples. HA-8180V variant mode was also compared against the Trinity ultra2 A1c analyzer for 50 samples containing hemoglobin variants (HbC 14, HbS 14, HbD 12, and HbE 10).

RESULTS

The within-run and total CVs were <0.01 and 0.75% at low HbA1c concentration and 0.46 and 0.63% at high HbA1c concentration, respectively. Linearity was shown in the concentration range 3.4-18.1% HbA1c, carryover was 0.00%, and stability values were excellent. Method comparison demonstrated a high concordance between methods.

CONCLUSION

The eighth generation ADAMS HA-8180V A1c analyzer demonstrated high analytical performance adequate for routine clinical use.

HbA mutation causing false-normal HbA1c results determined by HPLC in a patient with type 2 diabetes mellitus: A case report

Glycated hemoglobin A1c (HbA1c) is a convenient measure of long-term blood glucose concentrations and it is an accepted diagnostic test for type 2 diabetes mellitus (T2DM). The present study reported on a female patient with T2DM, whose fasting blood glucose and glycated albumin levels were elevated, while the HbA1c levels were in the normal range, which was inconsistent with the patient's clinical diagnosis. In the subsequent analysis, genomic DNA was extracted from the patient's blood and the HbA genes were analyzed by Sanger sequencing. The results indicated that the patient's HbA α1/2-chain genes had no mutations, while two HbA β-chain gene mutations were present, including an HBB:c.9T>C variant and a Hb G-Coushatta variant. The HBB:c.9T>C variant is a silent mutation that has no effect on HbA1c levels when detected by ion-exchange high-performance liquid chromatography (HPLC), while the Hb G-Coushatta variant may cause a discrepancy between blood glucose control and HbA1c levels when detected by ion-exchange HPLC. These results suggested that the Hb G-Coushatta variant gave rise to the false-normal result regarding HbA1c levels when detected by ion-exchange HPLC that was inconsistent with the clinical manifestations in this patient.

Association of hemoglobin H (HbH) disease with hemoglobin A1c and glycated albumin in diabetic and non-diabetic patients

OBJECTIVES

Hemoglobin A1c (HbA1c) and glycated albumin (GA) are glycemic control status indicators in patients with diabetes mellitus. Hemoglobin H (HbH) disease is a moderately severe form of α-thalassemia. Here we examine the usefulness of HbA1c and GA in monitoring glycemic control in patients with HbH disease.

METHODS

HbA1c, GA, and an oral glucose tolerance test were performed in 85 patients with HbH disease and 130 healthy adults. HbA1c was measured using five methods, including two systems based on cation-exchange high-performance liquid chromatography (Variant II Turbo 2.0 and Bio-Rad D100), a capillary zone electrophoresis method (Capillarys 3 TERA), a boronate affinity HPLC method (Premier Hb9210), and an immunoassay (Cobas c501).

RESULTS

Significant lower levels of HbA1c were observed in patients with HbH disease than in healthy adults. In contrast, GA showed no statistically significant differences between participants with and without HbH disease. A considerable number of diabetic patients with HbH disease would be missed if using HbA1c as a diagnostic criterion for diabetes mellitus.

CONCLUSIONS

GA but not HbA1c is suitable for monitoring glycemic control in patients with HbH disease that can modify the discriminative ability of HbA1c for diagnosing diabetes.

Low-carbohydrate dietary pattern on glycemic outcomes trial (ADEPT) among individuals with elevated hemoglobin A1c: study protocol for a randomized controlled trial

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a major cause of morbidity and mortality globally. Strong evidence supports the importance of diet and other lifestyle factors in preventing T2DM. Among individuals with T2DM, low-carbohydrate diets lead to decreases in hemoglobin A1c (HbA1c). However, research on the effects of low-carbohydrate diets on glycemic outcomes among individuals not currently on glucose-lowering medications who have elevated HbA1c is limited.

METHODS

The objective of this randomized controlled trial is to study the effect of a healthy low-carbohydrate diet achieved through behavioral intervention and key food supplementation compared with usual diet on HbA1c and other metabolic risk factors among individuals with HbA1c from 6.0 to 6.9% who are not on glucose-lowering medications. In this parallel trial, 150 participants will be randomized to the intervention or control group for 6 months. The healthy low-carbohydrate diet target is < 40 g of net carbohydrates during the first 3 months and < 40 to 60 net grams for months 3 to 6. This diet is characterized by abundant unsaturated fat and protein, high-fiber foods such as non-starchy vegetables and nuts, and minimal refined carbohydrates. The primary outcome is the difference in HbA1c change from baseline to 6 months in the intervention compared with usual diet group. Secondary outcomes include differences between groups in 6-month changes in fasting glucose, systolic blood pressure, total-to-high-density lipoprotein (HDL) cholesterol ratio, and body weight. Exploratory outcomes include differences in 6-month changes in fasting insulin, homeostasis model assessment of insulin resistance, diastolic blood pressure, waist circumference, and 10-year cardiovascular disease risk. An intention-to-treat analysis will be used.

DISCUSSION

We expect that the results from this study will lead to new approaches for developing and implementing dietary approaches (other than the most commonly used reduced fat diet) that will substantially reduce risk of cardiometabolic disease among adults with or at high risk of T2DM. The study intervention involves behavioral counseling and promotes consumption of dietary components thought to reduce risk of cardiometabolic disease and has expected applicability in clinical practice.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03675360 . Registered on September 18, 2018 (prior to enrolment of the first participant).

Unexpected HbA1c results in the presence of three rare hemoglobin variants

Hemoglobin (Hb) variants, characterized by structural abnormalities in the globin chains, are among the most common inherited disorders. It has been shown that Hb variant remains an important cause of erroneous HbA_1c results. Thus, it is important to be aware of the extent of the interference of each Hb variant encountered to avoid reporting unreliable results. However, the effects of many types of Hb variants on the measurement of HbA_1c remain unclear. Here, we describe three rare Hb variants, Hb J-Tashikuergan [HBA2: c.59 C > A], Hb Pyrgos [HBB: c.251G > A], and Hb Hope [HBB: c.410 G > A], which lead to extremely high values (>25%) determined by Variant II Turbo 2.0. We further investigated their effects on HbA_1c measurement by an HPLC system (Bio-Rad D100), a CE system (Sebia Capillarys 3 TERA), a boronate affinity chromatography system (Premier Hb9210), and an immunoassay method (Roche Diagnostics), and found that these Hb variants severely interfered with HbA_1c measurement by Variant II Turbo 2.0 and Bio-Rad D100. This study demonstrates that patients with abnormally high HbA_1c levels should be highly suspected of carrying Hb variants. When the HbA_1c results are considered unreliable, other indicators such as glycated albumin may be a possible alternative to HbA_1c in diabetic patients.

Potential of MALDI-TOF mass spectrometry to overcome the interference of hemoglobin variants on HbA1c measurement

Objectives

Hemoglobin (Hb) variants remain an important cause of erroneous HbA1c results. We present an approach to overcome the interference of Hb variants on HbA1c measurements using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

Methods

Samples containing or not containing Hb variants were analyzed for HbA1c using an MALDI-TOF MS system (QuanTOF) and a boronate affinity comparative method (Ultra2). For QuanTOF, two sets of HbA1c values were obtained through α- and β-chain glycation.

Results

A robust correlation between the glycation degrees of the α- and β-chains was found, and HbA1c values derived from α- and β-chain glycation correlated well with the Ultra2 results. Statistically significant differences (p<0.01) were found for all the Hb variants tested. When using the conventional β-chain glycation to determine HbA1c, clinically significant differences were only found among samples containing β-chain variants detected by QuanTOF (i.e., Hb J-Bangkok, Hb G-Coushatta, and Hb G-Taipei). In contrast, based on α-chain glycation, no clinically significant differences were found for these three variants.

Conclusions

In addition to conventional β-chain glycation, α-chain glycation can be used to calculate HbA1c values. The interference of Hb variants on HbA1c quantification can be overcome by employing the glycation of the globin chain without a genetic variant to estimate HbA1c values.

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.

Glycated albumin as a diagnostic tool in diabetes: An alternative or an additional test?

Introduction

Studies have revealed that glycated albumin (GA) is a useful alternative to HbA_1c under conditions wherein the latter does not reflect glycaemic status accurately. Until now, there are few studies with non-Asians subjects that report on the validity of GA test in diagnosis of type 2 diabetes mellitus (DM). Thus, the aim of this study was to assess the clinical utility of GA in diagnosis of DM.

Materials and methods

This diagnostic test accuracy study was performed in 242 Brazilian individuals referred for OGTT in a tertiary university hospital. ROC curves were used to access the performance of GA and HbA_1c in the diagnosis of DM by oral glucose tolerance test (OGTT).

Results

OGTT, HbA_1c and GA were performed in all 242 participants (40.5% male, age 54.4 ± 13.0 years [mean ± SD], body mass index 28.9 ± 6.3 kg/m²). DM by OGTT was detected in 31.8% of individuals. The equilibrium threshold value of GA ≥14.8% showed sensitivity of 64.9% and specificity of 65.5% for the diagnosis of DM. The AUC for GA [0.703 (95% CI 0.631–0.775)] was lower than for HbA_1c [0.802 (95% CI 0.740–0.864)], p = 0.028. A GA value of 16.8% had similar accuracy for detecting DM as defined by HbA_1c ≥6.5% (48 mmol/mol) with sensitivity of 31.2% and specificity of 93.3% for both tests. However, GA detects different subjects from those detected by HbA_1c and OGTT.

Conclusions

GA detected different individuals with DM from those detected by HbA_1c, though it showed overall diagnostic accuracy similar to HbA_1c in the diagnosis of DM. Therefore, GA should be used as an additional test rather than an alternative to HbA_1c or OGTT and its use as the sole DM diagnostic test should be interpreted with caution.

Increased Levels of Glycated Hemoglobin A1c and Iron Deficiency Anemia: A Review

Worldwide, the prevalence of diabetes remains high. Studies have shown that iron deficiency anemia (IDA) is associated with increased levels of glycated hemoglobin A1c (HbA1c), but the mechanism remains unclear. Hematological changes, iron metabolism, study methodology, and other factors could affect the results of diagnostic investigations, leading to false results. Red blood cell turnover in the bone marrow and the quality and heterogeneity of erythrocytes may influence the rate of hemoglobin glycation. By changing the structure of hemoglobin and inducing peroxidation, iron deficiency accelerates glycation. This review aims to discuss the possible causes of the association between increased levels of HbA1c and IDA.

Effects of common hemoglobin variants on HbA1c measurements in China: results for α- and β-globin variants measured by six methods

BACKGROUND

HbA1c is a widely used biomarker for diabetes mellitus management. Here, we evaluated the accuracy of six methods for determining HbA1c values in Chinese patients with common α- and β-globin chains variants in China.

METHODS

Blood samples from normal subjects and individuals exhibiting hemoglobin variants were analyzed for HbA1c, using Sebia Capillarys 2 Flex Piercing (C2FP), Bio-Rad Variant II Turbo 2.0, Tosoh HLC-723 G8 (ver. 5.24), Arkray ADAMS A1c HA-8180V fast mode, Cobas c501 and Trinity Ultra2 systems.

RESULTS

DNA sequencing revealed five common β-globin chain variants and three common α-globin chain variants. The most common variant was Hb E, followed by Hb New York, Hb J-Bangkok, Hb G-Coushatta, Hb Q-Thailand, Hb G-Honolulu, Hb Ube-2 and Hb G-Taipei. Variant II Turbo 2.0, Ultra2 and Cobas c501 showed good agreement with C2FP for most samples with variants. HLC-723 G8 yielded no HbA1c values for Hb J-Bangkok, Hb Q-Thailand and Hb G-Honolulu. Samples with Hb E, Hb G-Coushatta, Hb G-Taipei and Hb Ube-2 produced significant negative biases for HLC-723 G8. HA-8180V showed statistically significant differences for Hb E, Hb G-Coushatta, Hb G-Taipei, Hb Q-Thailand and Hb G-Honolulu. HA-8180V yielded no HbA1c values for Hb J-Bangkok. All methods showed good agreement for samples with Hb New York.

CONCLUSIONS

Some common hemoglobin variants can interfere with HbA1c determination by the most popular methods in China.

Hb I: A α-globin chain variant causing unexpected HbA1c results

BACKGROUND

HbA_1c is the standard bio-marker for glycemic control in patients with diabetes. Here, we report a α-globin chain variant and evaluate its effect on HbA_1c measurements.

METHODS

A 21-year-old female was suspected of harboring a hemoglobin variant following HbA_1c measurement during a routine examination using Variant II Turbo 2.0 (Bio-Rad). An oral glucose tolerance test was performed using an AU5800 clinical chemistry system (Beckman Coulter). HbA_1c was reanalyzed using D10 (Bio-Rad), Capillarys 2 Flex Piercing (Sebia), and Premier Hb9210 (Trinity Biotech). Hemoglobin analysis was performed using high-performance liquid chromatography (HPLC) on the Bio-Rad Variant II (β-thalassemia short program) and capillary electrophoresis (CE, Capillarys 2 Flex Piercing, Hb program). Sanger sequencing of α and β genes was also conducted.

RESULTS

HbA_1c was initially measured at 24.2% using Variant II Turbo 2.0. For the oral glucose tolerance test, fasting glucose, 1-hour, and 2-hour levels were recorded as 4.25, 7.89, and 5.34 mmol/L, respectively. Subsequently, HbA_1c values determined by D10, Capillarys 2 Flex Piercing (HbA_1c program), and Premier Hb9210 were 4.5% (26 mmol/mol), no HbA_1c value, and 4.8 (29 mmol/mol), respectively. Hemoglobin analyzed using CE and HPLC revealed an abnormal hemoglobin. Sanger sequencing identified a transversion mutation of the α2 gene [CD16(AAG>GAG), Lys>Glu, HBA2: c.49 A>G], corresponding to a Hb I variant.

CONCLUSION

An unusually high HbA_1c or discordance between blood sugar and HbA_1c values should alert about the possibilities of hemoglobin variants.

New HPLC instrument performance evaluation in HbA1c determination and comparison with capillary electrophoresis

Glycated hemoglobin (HbA_1c) measurement provides the most important medium to long-term marker of time-averaged glycemic status. Its relationship to clinical outcome in diabetes has been convincingly demonstrated for both type 1 and type 2 diabetes. The main HbA_1c measurement methods for clinical routine are as follows: ion-exchange chromatography; affinity chromatography, capillary electrophoresis, immunoassay and enzymatic methods. In this study, we evaluated the analytical performances of a new HPLC instrument (Tosoh HLC-723 G11 in the VAR mode) in HbA_1c analysis and compared it with a capillary electrophoresis instrument (Sebia Capillarys 2 Flex Piercing). HbA_1c analysis was performed in parallel by both methods for 250 samples randomly chosen from healthy and diabetic subjects at 'Tor Vergata' University Hospital of Rome. Tosoh HLC-723 G11 showed good reproducibility for 10 days both in quality controls and in samples analyzed (%CV < 2%). We found good linearity for HbA1c values ranging from 15 mmol/mol (3.5%) to 178 mmol/mol (18.5%), with a correlation coefficient R² = 1. In a comparison between Tosoh HLC-723 G11 and Capillarys 2FP a good correlation (r = 0.99) was found; however, Tosoh HLC-723 G11 showed higher values in the low range of HbA_1c and lower in the high range (Tosoh HLC-723 G11 = 4.3043 + 0.913 Capillarys 2FP; p < 0.001). Tosoh HLC-723 G11 showed good repeatability, reproducibility, accuracy and automated simplicity, and it seemed suitable for routine use in clinical chemistry laboratories.

Hemoglobin S monitoring on TOSOH G8 in hemoglobin A1c mode in case of urgent red blood cell exchange

BACKGROUND

Pre- and post-transfusion hemoglobin S (HbS) levels are used to document the efficacy of red blood cell exchange (RCE) in patients with sickle cell disease (SCD). In case of urgent RCE a 24/7 short turn-around time (STAT) analysis, with the ability to identify and quantify HbS, is warranted. The use of TOSOH G8 (Tosoh Europe) is evaluated for this purpose, using the variant HbA1c mode.

METHODS

Analytical performance of the HbS analysis on TOSOH G8 in variant HbA1c mode was evaluated, including assessment of imprecision and linearity for HbS. In addition, a comparison study between TOSOH G8 and Minicap Flex Piercing (FP) system CZE (Sebia) using 32 HbS samples (HbS range: 9%-93%) was carried out to evaluate analytical and clinical concordance.

RESULTS

Total HbS imprecision was 1.77% and 0.31% for a sickle cell trait and a sickle cell anemia sample, respectively. An acceptable linearity (HbS range: 6%-88%) was observed (R²  > .99). Passing-Bablok regression analysis showed a significant proportional bias; however, a good analytical concordance (r > .95) was found. Our results suggested that TOSOH G8 underestimated HbS results compared with those of Minicap FP system (mean difference: -3.54%), especially in samples with a high HbS concentration.

CONCLUSION

Hemoglobin S results obtained with TOSOH G8 in variant HbA1c mode are clinically acceptable to monitor urgent RCE. The observed underestimation will not alter clinical decision-making.

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.

Higher degree of glycation of hemoglobin S compared to hemoglobin A measured by mass spectrometry: Potential impact on HbA1c testing

BACKGROUND

Glycated hemoglobin (GHb), reported as HbA1c, is used as marker of long-term glycemia for diabetic patients. HbA1c results from boronate affinity methods are generally considered to be unaffected by most hemoglobin variants; this assumes comparable glycation of variant and non-variant (HbAA) hemoglobins. In this report, glycation of HbA beta chain (βA) and HbS beta chain (βS) for the most common Hb variant trait (HbAS) are examined.

METHODS

We analyzed 41 blood samples from subjects with HbAS, both with and without diabetes. Using LC-MS, ratios of glycated HbS to glycated HbA were determined by comparison of areas under the curves from extracted ion chromatograms.

RESULTS

Glycation of βS chains was significantly higher (p<0.001) than βA chains; this difference was consistent across subjects. Total (α+β) glycated HbAS was theoretically estimated to be ~5% higher than glycated HbAA.

CONCLUSION

This novel mass-spectrometric approach described allows for relative quantification of glycated forms of βS and βA. Although βS glycation was significantly higher than that of βA, the difference in total glycation of HbAS versus HbAA was smaller and unlikely to impact clinical interpretation of boronate affinity HbA1c results. These data support the continued use of boronate affinity to measure HbA1c in patients with HbAS.