Two patients with α-chain hemoglobin variant Hb Q-Iran detected by measuring hemoglobin A1c using the variant mode of the HA-8180V HPLC analyzer

Hemoglobin variants are often discovered when hemoglobin A1c (HbA1c) levels measured with a high-performance liquid chromatography (HPLC) system in fast mode are found to be low. The HA-8180V HPLC analyzer by Arkray offers two measurement modes: fast mode (FM) and variant mode (VM). Two Japanese patients with α-chain variant Hb Q-Iran detected incidentally after analyses with the HA-8180V in VM showed an abnormal peak, are presented. The first patient was a man in his 70 s, and the second patient was a man in his 50 s. Both were non-diabetic, but their results from HbA1c measurement in VM showed an abnormal peak. The VM-HbA1c, FM-HbA1c, and HbA1c measured by enzymatic assay and glycated albumin levels of the two patients were all within the reference ranges. They were diagnosed as having Hb Q-Iran (α2-75Asp → His) by globin gene analysis. It is difficult to detect α-chain hemoglobin variants based on abnormal FM-HbA1c levels, but measuring HbA1c in VM is useful for efficiently detecting hemoglobin variants.

Detectability of and interference by major and minor hemoglobin variants using a new-generation ion-exchange HPLC system with two switchable analysis modes

Objectives

High-performance liquid chromatography (HPLC) is commonly used to measure hemoglobin A1c (HbA1c) levels and detect hemoglobin variants (Hb-Vars). HLC-723GR01 (GR01) is a new-generation automated ion-exchange HPLC system with two switchable analysis modes, namely short (30 s/test) and long modes (50 s/test). We evaluated the general performance of both analysis modes of GR01 for quantifying HbA1c and detecting Hb-Vars.

Design and methods

We evaluated the instrument's precision based on CLSI protocol EP-05-A3. A comparison of the two analysis modes of GR01 against the standard mode of HLC-723G11 was performed on 100 whole blood samples. The GR01 long mode was compared with affinity HPLC (AF-HPLC) for detecting common Hb-Vars (HbE, HbD, HbS, and HbC, >20 samples). To examine the detection capability for minor Hb-Vars, we analyzed 26 Hb-Vars using multiple analyzers, including both analysis modes of GR01.

Results

Both modes of GR01 had within-laboratory coefficients of variation of ≤1.0 % from four samples with HbA1c concentrations of 32-86 mmol/mol. Good correlation was observed between GR01 and HLC-723G11. The results for HbA1c detection in the presence of the major variants revealed a strong correlation between the long mode of GR01 and AF-HPLC (r = 0.986-0.998), and the difference biases ranged 0.1-1.9 mmol/mol. In the long mode, only one variant had a difference bias exceeding 14 % [10 % (%NGSP)].

Conclusion

The two analysis modes of GR01 were fast and had high accuracy and reproducibility, indicating their utility for routine clinical use in measuring HbA1c samples with Hb-Vars.

Quantitation of glycated albumin by isotope dilution mass spectrometry

BACKGROUND

Glycated albumin is considered an alternative glycemic indicator in certain situations where HbA1c does not accurately reflect glycemic status. These patient cases are usually associated with decreased erythrocyte lifespan, gestational diabetes, or end-stage renal disease. The aim of our study was to develop an assay for absolute quantitation of glycated albumin based on isotope dilution liquid chromatography-mass spectrometry.

METHODS

The plasma samples were reduced/alkylated, spiked with isotope-labeled standards RQIKKQTALV(D₈)E and RQIKK(fructosyl)QTALV(D₈)E and enzymatically digested by Glu-C. The samples were analyzed on an LC-MS system. Two MRM transitions (M³⁺ → (b₉-3H₂O)²⁺ and M³⁺ → (b₁₀-3H₂O)²⁺ or M³⁺ → b₉²⁺ and M³⁺ → b₁₀²⁺) were used for each peptide, then the percentage of glycation (MS GA%) was calculated.

RESULTS

The comparison study demonstrated a good linear correlation between our LC-MS/MS and Lucica method with r² = 0.95. The intra-day CV for the low HbA1c sample was 2.2%, while CV for the high HbA1c sample was 0.64%. Inter-day CV for low HbA1c sample was 5.6%, while the CV for the high HbA1c sample was 5.7%. We found the LLOQ to be 0.12 nmol/ml for the non-glycated and glycated peptide. No interference from hemoglobin was observed up to 500 mg/dL concentration.

CONCLUSIONS

This is the first implementation of isotope dilution LC-MS assay for glycated albumin with simultaneously quantitation of glycated and non-glycated peptides. The method includes a simple sample preparation and has demonstrated a good analytical performance.

Emerging Diabetic Novel Biomarkers of the 21st Century

Diabetes is a growing epidemic with estimated prevalence of infected to reach ~592 million by the year 2035. An effective way to approach is to detect the disease at a very early stage to reduce the complications and improve lifestyle management. Although several traditional biomarkers including glucated hemoglobin, glucated albumin, fructosamine, and 1,5-anhydroglucitol have helped in ease of diagnosis, there is lack of sensitivity and specificity and are inaccurate in certain clinical settings. Thus, search for new and effective biomarkers is a continuous process with an aim of accurate and timely diagnosis. Several novel biomarkers have surged in the present century that are helpful in timely detection of the disease condition. Although it is accepted that a single biomarker will have its inherent limitations, combining several markers will help to identify individuals at high risk of developing prediabetes and eventually its progression to frank diabetes. This review describes the novel biomarkers of the 21st century, both in type 1 and type 2 diabetes mellitus, and their present potential for assessing risk stratification due to insulin resistance that will pave the way for improved clinical outcome.

Estimation of the hemoglobin glycation rate constant

In a previous study, a method of obtaining mean erythrocyte age ([Formula: see text]) from HbA1c and average plasma glucose (AG) was proposed. However, the true value of the hemoglobin glycation constant ([Formula: see text] dL/mg/day), required for this model has yet to be well characterized. Another study also proposed a method of deriving [Formula: see text] from erythrocyte creatine (EC). Utilizing these formulae, this study aimed to determine a more accurate estimate of [Formula: see text]. One hundred and seven subjects including 31 patients with hemolytic anemia and 76 subjects without anemia were included in this study. EC and HbA1c data were analyzed, and [Formula: see text] using HbA1c, AG and the newly-derived constant, [Formula: see text] were compared to [Formula: see text] using traditional [Formula: see text] in three patients whose data were taken from previous case studies. A value of [Formula: see text] dL/mg/day was determined for [Formula: see text]. [Formula: see text] using HbA1c, AG and [Formula: see text] were found to no be significantly different (paired t-test, [Formula: see text]) to [Formula: see text] using traditional [Formula: see text]. [Formula: see text] enables the estimation of [Formula: see text] from HbA1c and AG.

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

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

Hereditary spherocytosis diagnosed with extremely low glycated hemoglobin compared to plasma glucose levels

Glycated hemoglobin (HbA1c) is an important indicator of glycemic control in patients with diabetes. High-performance liquid chromatography (HPLC) is the most commonly used method for measuring HbA1c levels; as HPLC measures all hemoglobin types, the values can be influenced by hemoglobin variants. Moreover, as HPLC-HbA1c levels are low in some diseases, including hemolytic anemia, it may be difficult to differentiate hemoglobin variants from these diseases based on HPLC-HbA1c levels alone. Similar HbA1c values using both HPLC and immunoassays (IAs) are noted for these diseases, while discrepancies are noted in the case of hemoglobin variants. Herein, we describe our process of differential diagnosis for hereditary spherocytosis, the most common inherited hemolytic anemia, in a 56-year-old man presenting with a low HPLC-HbA1c level compared to the glucose concentration, concomitant with anemia, jaundice, hyperbilirubinemia, cholelithiasis, and splenomegaly. There was a discrepancy between HbA1c levels measured with HPLC and IAs and glycated albumin levels. The possibility of hemoglobin variants was unlikely, based on the chromatography and isoelectric focusing results. The haptoglobin levels and reticulocyte counts were low and high, respectively. The direct and indirect Coomb's tests were negative. The presence of spherocytes on blood smears and flow cytometric analysis of the eosin-5-maleimide binding test supported a diagnosis of hereditary spherocytosis. We recommend that when a discrepancy between HPLC-HbA1c levels and glucose concentrations is noted, clinicians should consider hemolysis or hemoglobin variants as the diagnosis. It should be considered that a discrepancy between HbA1c levels measured with HPLC and IAs does not specifically exclude hemolysis.

Hb Phnom Penh Showing Falsely High or Reasonable HbA1c Values Depending on the Type of High-performance Liquid Chromatography System

We herein report a 50-year-old Chinese woman with Hb Phnom Penh (α117Phe-Ile-α118Thr) showing high or reasonable HbA1c values depending on the type of high-performance liquid chromatography (HPLC) system. A high HbA1c value of 7.5% (HPLC assay: G9) and a reasonable HbA1c value of 5.2% (assay unknown) were observed. Therefore, the patient was refereed to our hospital; the oral glucose tolerance test showed normal glucose tolerance. The HbA1c values measured by an enzymatic assay, immunoassay, and affinity assay, as well as most HPLC assays were within the reference range, whereas those measured by the Tosoh HPLC systems were high.

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

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

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.

Analysis of Hemoglobin Glycation Using Microfluidic CE-MS: A Rapid, Mass Spectrometry Compatible Method for Assessing Diabetes Management

Diabetes has become a significant health problem worldwide with the rate of diagnosis increasing rapidly in recent years. Measurement of glycated blood proteins, particularly glycated hemoglobin (HbA1c), is an important diagnostic tool used to detect and manage the condition in patients. Described here is a method using microfluidic capillary electrophoresis with mass spectrometry detection (CE-MS) to assess hemoglobin glycation in whole blood lysate. Using denaturing conditions, the hemoglobin (Hb) tetramer dissociates into the alpha and beta subunits (α- and β-Hb), which are then separated via CE directly coupled to MS detection. Nearly baseline resolution is achieved between α-Hb, β-Hb, and glycated β-Hb. A second glycated β-Hb isomer that is partially resolved from β-Hb is detected in extracted ion electropherograms for glycated β-Hb. Glycation on α-Hb is also detected in the α-Hb mass spectrum. Additional modifications to the β-Hb are detected, including acetylation and a +57 Da species that could be the addition of a glyoxal moiety. Patient blood samples were analyzed using the microfluidic CE-MS method and a clinically used immunoassay to measure HbA1c. The percentage of glycated α-Hb and β-Hb was calculated from the microfluidic CE-MS data using peak areas generated from extracted ion electropherograms. The values for glycated β-Hb were found to correlate well with the HbA1c levels derived in the clinic, giving a slope of 1.20 and an R(2) value of 0.99 on a correlation plot. Glycation of human serum albumin (HSA) can also be measured using this technique. It was observed that patients with elevated glycated Hb levels also had higher levels of HSA glycation. Interestingly, the sample with the highest HbA1c levels did not have the highest levels of glycated HSA. Because the lifetime of HSA is shorter than Hb, this could indicate a recent lapse in glycemic control for that patient. The ability to assess both Hb and HSA glycation has the potential to provide a more complete picture of a patient's glycemic control in the months leading up to blood collection. The results presented here demonstrate that the microfluidic CE-MS method is capable of rapidly assessing Hb and HSA glycation from low volumes of whole blood with minimal sample preparation and has the potential to provide more information in a single analysis step than current technologies.

Is glycated albumin useful for differential diagnosis between fulminant type 1 diabetes mellitus and acute-onset autoimmune type 1 diabetes mellitus?

BACKGROUND

Markedly elevated plasma glucose and relatively low HbA1c compared to plasma glucose is one diagnostic criterion for fulminant type 1 diabetes mellitus (FT1DM). Glycated albumin (GA) is a glycemic control marker that reflects glycemic control in shorter period than HbA1c. This study investigated whether GA is useful for differential diagnosis between FT1DM and acute-onset autoimmune type 1 diabetes mellitus (T1ADM) or not.

METHODS

This study included 38 FT1DM patients and 31 T1ADM patients in whom both HbA1c and GA were measured at the time of diagnosis.

RESULTS

In FT1DM patients, as compared to T1ADM patients, both HbA1c and GA were significantly lower (HbA1c; 6.6±0.9% vs. 11.7±2.6%, P<0.0001, GA; 22.9±4.8% vs. 44.3±8.3%, P<0.0001). For differential diagnosis between FT1DM and T1ADM, ROC analysis showed that the optimum cut-off value for GA was 33.5% with sensitivity and specificity of 97.4% and 96.8%, respectively, while the optimum cut-off value for HbA1c was 8.7% with sensitivity and specificity of 100% and 83.9%, respectively.

CONCLUSIONS

GA also may be useful for the differential diagnosis between FT1DM and T1ADM when the cut-off value can be set at 33.5%.

Alternative biomarkers for assessing glycemic control in diabetes: fructosamine, glycated albumin, and 1,5-anhydroglucitol

The growing attention to alternative glycemic biomarkers including fructosamine, glycated albumin (GA), 1,5-anhydroglucitol (1,5-AG), is attributable to the limitations of the glycated hemoglobin (HbA1c) assay. It is important to recognize the conditions in which HbA1c levels may be difficult to interpret. Serum fructosamine and GA have been proposed useful tools for monitoring of short-term glycemic control. These biomarkers not only reflect well glycemic control in hematologic disorder, but also represent postprandial glucose fluctuation. Serum 1,5-AG may be useful for estimating within-day glucose variation. Use of these nontraditional tests can be more helpful in the management of diabetes as complement traditional measures. Further larger cohort studies are warranted to determine whether nontraditional biomarkers have potential utility for early diagnosis, management of diabetes, and prevention of diabetic complications.

1,5-Anhydroglucitol and glycated albumin in glycemia

The main purpose of treating diabetes is to prevent the onset and the progression of diabetic chronic complications. Since the mechanism of onset of chronic complications is still not well understood, the main strategy to achieve this purpose is to bring the plasma glucose level in diabetic patients as close as possible to that in healthy subjects and try to maintain good glycemic control over the long term. Glycated hemoglobin (HbA1c), glycated albumin (GA), fructosamine, and 1,5-anhydroglucitol (1,5 AG) are used for evaluating glycemic control. At present, HbA1c is widely used as a gold standard index for glycemic control in clinical practice. While HbA1c reflects the long-term glycemic control state (for the past 1-2 months), it does not accurately reflect glycemic control in the clinical state in which glycemic control improves or deteriorates in the short-term. It is also known that HbA1c in patients with hematological disorders such as anemia and variant hemoglobin shows an abnormal value. In addition, HbA1c mainly reflects the mean plasma glucose but does not reflect the postprandial plasma glucose. On the other hand, GA and 1,5-AG reflect intermediate- or short-term glycemic control and are not influenced by hemoglobin metabolism. While 1,5-AG is known to reflect the postprandial plasma glucose, it was shown recently that GA also reflects the postprandial plasma glucose. This chapter summarizes the measurement methods, usage methods, evidence, and problems concerning such indices for glycemic control.

Glycated albumin; clinical usefulness

The main purpose of treating diabetes is to prevent the onset and progression of diabetic chronic complications. Since the mechanism of onset of chronic complications is still not well understood, the main strategy to achieve this purpose is to bring plasma glucose levels as close as possible to those in healthy subjects and maintain good glycemic control over the long term. Since glycation among various proteins is increased in diabetic patients compared with non-diabetic subjects, glycated protein can be used as a glycemic control indicator. Currently, among these glycated proteins, HbA1c is used as the gold standard of glycemic control indicators. However, HbA1c does not accurately reflect the actual status of glycemic control in some conditions with rapid changes in glycemic control and in patients with anemia (hemolytic anemia, iron deficiency anemia, etc.) and variant hemoglobin. In comparison, glycated albumin (GA) more accurately reflects changes in plasma glucose during the short term and postprandial plasma glucose. GA also reflects glycemic control in patients with hematologic disorders whereas GA does not reflect glycemic control in patients with disorder of albumin metabolism. GA is a glycemic control indicator which overcomes most of the disadvantages of HbA1c, and could be therefore expected to replace HbA1c as the standard glycemic control indicator in the near future. However, it is necessary to accumulate more evidences from large research studies on the effective directions for measuring GA.

Degree of discrepancy between HbA1c and glycemia in variant hemoglobin is smaller when HbA1c is measured by new-type Arkray HPLC compared with old-type HPLC

OBJECTIVES

Although variant hemoglobin mainly demonstrates inappropriate HbA1c values measured by high-performance liquid chromatography (HPLC), these values differ depending on the HPLC model. In the 1990s, old-type HPLC models were replaced with new-type HPLC models which could separate stable HbA1c from labile HbA1c and modified hemoglobin. This study compared HbA1c values in subjects with variant hemoglobin measured using old-type Arkray HPLC (HA-8150) and new-type Arkray HPLC (HA-8160 or HA-8180).

DESIGN AND METHODS

This study included non-diabetic subjects with apparently low HbA1c values who had variant hemoglobins due to a β-chain heterozygous mutation. HbA1c was measured by old-type HPLC in 28 subjects with 12 variant hemoglobins (group 1) and new-type HPLC in six subjects with four variant hemoglobins (group 2). When HbA1c was measured by HPLC (HPLC-HbA1c), HbA1c measured by immunoassay (IA-HbA1c) and glycated albumin (GA) were also measured.

RESULTS

IA-HbA1c and GA did not significantly differ between both groups. However, HPLC-HbA1c in group 2 was significantly higher than that in group 1 (group 1: 2.9 ± 0.7% vs. group 2: 3.7 ± 0.2%, P = 0.006).

CONCLUSIONS

When HbA1c in subjects with variant hemoglobin is measured by new-type Arkray HPLC, the degree of discrepancy between HbA1c and glycemia is smaller compared with that measured by old-type HPLC.