Clinical Advances in Hemoglobin A1c Measurement: The Clinical Use of Hemoglobin A1c

Hemoglobin A1c (HbA1c) has been accepted as an index of glycemic control since the mid-1970s and is the best marker for diabetic microvascular complications. Clinically, it is now used to assess glycemic control in people with diabetes. Assays are most reliable when certified by the National Hemoglobin Standardization Program but are subject to confounders and effect modifiers, particularly in the setting of hematologic abnormalities. Other measures of chronic glycemic control—fructosamine and 1,5-anhydroglucitol—are far less widely used. The relationship of HbA1c to average blood glucose was intensively studied recently, and it has been proposed that this conversion can be used to report an “estimated average glucose, eAG” in milligrams/deciliter or millimolar units rather than as per cent glycated hemoglobin. Finally, HbA1c has been proposed as a useful method of screening for and diagnosing diabetes.     

Hemoglobin variants and determination of glycated hemoglobin (HbA1c)

Measurement of glycated hemoglobin in diabetic patients is an established procedure for evaluating long-term control of diabetes. The Diabetes Control and Complications Trial (DCCT), as well as the United Kingdom Prospective Diabetes Study (UKPDS), confirmed the direct relationship between the degree of glycemic control as estimated by glycohemoglobin (GHb) determinations and the development and progression of long-term complications in diabetic patients. Samples with known interferences of HbA(1c) determination as hemoglobinopathies are specifically excluded from certification testing and there are no guidelines or requirements for comparability of samples containing hemoglobin (Hb) variants. This paper reviews the interference of Hb variants on determination methods of glycated hemoglobin as they result in false HbA(1c) results.     

Control of Hemoglobin Synthesis in Fetal Erythroid Cells by L-Thyroxine

Fetal mouse liver cells were incubated in the presence of L-thyroxine. Globin synthesis by cells from the 13th to 15th days of gestation was stimulated by the presence of the hormone. Although protein synthesis by cells from the 17th day of gestation was stimulated, the protein was not identified as globin. A tentative conclusion was drawn that fetal erythroid tissue may be preferentially stimulated by thyroid hormone.     

Hemoglobin Bassett produces low pulse oximeter and co-oximeter readings

Variant hemoglobins can have altered oxygen affinity and can produce changes in oximeter readings. We present a case of hemoglobin Bassett, a possible cause of low pulse oximeter and co-oximeter readings in a 63-year-old woman.     

Effects of Hemoglobin Variants on Hemoglobin A1c Values Measured Using a High-Performance Liquid Chromatography Method

Hemoglobin A1c (HbA1c) is routinely used to monitor long-term glycemic control and for diagnosing diabetes mellitus. However, hemoglobin (Hb) gene variants/modifications can affect the accuracy of some methods. The potential effect of Hb variants on HbA1c measurements was investigated using a high-performance liquid chromatography (HPLC) method compared with an immunoturbimetric assay. Fasting plasma glucose (FPG) and HbA1c levels were measured in 42 371 blood samples. Samples producing abnormal chromatograms were further analyzed to characterize any Hb variants. Fructosamine levels were determined in place of HbA1c levels when unstable Hb variants were identified. Abnormal HPLC chromatograms were obtained for 160 of 42 371 samples. In 26 samples HbS was identified and HbA1c results correlated with FPG. In the remaining 134 samples HbD, Hb Louisville, Hb Las Palmas, Hb N-Baltimore, or Hb Porto Alegre were identified and HbA1c did not correlate with FPG. These samples were retested using an immunoturbidimetric assay and the majority of results were accurate; only 3 (with the unstable Hb Louisville trait) gave aberrant HbA1c results. Hb variants can affect determination of HbA1c levels with some methods. Laboratories should be aware of Hb variants occurring locally and choose an appropriate HbA1c testing method.     

Fetal Hemoglobin Induction by Epigenetic Drugs

Fetal hemoglobin (HbF) inhibits the root cause of sickle pathophysiology, sickle hemoglobin polymerization. Individuals who naturally express high levels of HbF beyond infancy thus receive some protection from sickle complications. To mimic this natural genetic experiment using drugs, one guiding observation was that HbF is increased during recovery of bone marrow from extreme stress. This led to evaluation and approval of the cytotoxic (cell killing) drug hydroxyurea to treat sickle cell disease. Cytotoxic approaches are limited in potency and sustainability, however, since they require hematopoietic reserves sufficient to repeatedly mount recoveries from stress that destroys their counterparts, and such reserves are finite. HbF induction even by stress ultimately involves chromatin remodeling of the gene for HbF (HBG), therefore, a logical alternative approach is to directly inhibit epigenetic enzymes that repress HBG—implicated enzymes include DNA methyltransferase 1, histone deacetylases, lysine demethylase 1, protein arginine methyltransferase 5, euchromatic histone lysine methyltransferase 2 and chromodomain helicase DNA-binding protein 4. Clinical proof-of-principle that this alternative, noncytotoxic approach can generate substantial HbF and total hemoglobin increases has already been generated. Thus, with continued careful attention to fundamental biological and pharmacologic considerations (reviewed herein), there is potential that rational, molecular-targeted, safe and highly potent disease-modifying therapy can be realized for patients with sickle cell disease, with the accessibility and cost-effective properties needed for world-wide effect.     

Advances in Hemoglobin A1c Point of Care Technology

Measurement of hemoglobin A1c (A1C) has long been accepted as the best indicator of glucose control over time. Assays for A1C use technologies based on either charge differences (high-pressure liquid chromatography) or structure (boronate affinity or immunoassay combined with general chemistry). These technologies are generally employed in expensive laboratory instruments. More recently, A1C technology has been incorporated into point of care (POC) devices, allowing for immediate availability of A1C measurements, greatly facilitating diabetes care in both specialist and general practices. POC A1C tests should have acceptable performance, standardization to national reference, National Glycohemoglobin Standardization Program (NGSP) certification, simple operation without need for costly instrumentation, and Clinical Laboratory Improvement Amendments (CLIA) waiver. CLIA-waived POC technology includes Bio-Rad MicroMat™ II (distributed by Cholestech as GDX™) and the Axis-Shield Afinion,™ both of which utilize boronate affinity. The DCA 2000®+ utilizes combined immunoassay and general chemistry. These instruments cost $1000 to $3000 and require regular maintenance, making them appropriate only for high-volume physician offices. The newly improved A1CNow+™ also utilizes combined immunoassay and general chemistry, but the small, inexpensive, disposable monitor can be used by patients as well as by health care professionals. The new version of A1CNow+ has improved performance through recent introduction of automated solid state chemistry manufacturing, improved fluidics and automated assembly of the test cartridge, error-correcting software, and unitary meter calibration with factory calibration directly to the NGSP reference standard.     

Hemoglobin S levels in sickle cell trait individuals

Changes in Department of Defense regulations now permit persons with sickle cell trait to serve in all service branches. However, for purposes of the regulation, sickle cell trait is defined as 41% or less S hemoglobin. Our screening experience, based on 397 individuals with sickle cell trait, with quantitative scan of cellulose acetate electrophoretic sheets, indicates that 20-40% (depending on definition of terms) of individuals with sickle cell trait would be excluded by this criterion.     

Hemoglobin aggregation and pseudosickling in vitro of hemoglobin setif-containing erythrocytes

Erythrocytes from individuals heterozygous for hemoglobin Setif (α⁹⁴ Asp→Tyr) sickle in vitro without deoxygenation when incubated in chloride buffer due to hemoglobin aggregation. We now report quantitative studies of hemoglobin polymerization and deformability in these cells. Hemoglobin polymer gradually increased in intact cells during a 24 h incubation period at 24°C. After 24 hr, about 80% of the cells in 290 mosm sodium chloride buffer contained polymer which appeared as short rods compared to >99% containing polymer at 450 mOsm. Similar proportions of cells were morphologically sickled. Deformability of erythrocytes with 40% hemoglobin Setif incubated in 290 mOsm buffer at 37°C decreased to 80% of normal by 210 min but in 450 mOsm decreased to 50% after only 30 min as measured by the ektacytometer. However, at 4°C deformability remained normal even in 450 mOsm buffer. The solubility of gelled hemolysate containing 40% hemoglobin Setif was 24 g/dl and 21 g/dl at 290 and 459 mOsm buffer respectively. The gel persisted at 4°C with a solubility of 25 g/dl, but melted when dialyzed into sodium phosphate or potassium phosphate buffer. These data suggest that hemoglobin polymerization, reduced deformability, and sickling of hemoglobin Setif-containing erythrocytes are related to reduced hemoglobin solubility. The rate and extent of intracellular polymerization in vitro are considerably reduced (as in the case of sickle trait) compared with erythrocytes from individuals with sickle cell anemia. Hence, the slower kinetics of hemoglobin aggregation in hemoglobin Setif-containing cells provide an alternate system for studying hemoglobin aggregation in hemoglobin Setif-containing cells provide an alternate system for studying hemoglobin polymerization and abnormal rhelogy.     

Hematologic Profile and Lymphocyte Subpopulations in Hemoglobin SC disease: Comparison With Hemoglobin SS and Black Controls

Compared with subjects with homozygous SS disease (Hb SS), persons with hemoglobin SC (Hb SC) are known to have a more gradual loss of splenic function, a lower incidence of bacterial infections, and fewer end-organ failures. We studied hematological indices and lymphocyte subpopulations of 27 Hb SC subjects and compared them with 173 Hb SS patients and 131 black controls. Hb SC patients had higher hemoglobin levels than Hb SS subjects, lower total leukocyte, granulocyte, monocyte, and lymphocyte counts. Platelets decresed with age but not significantly, instead of incressing as among Hb SS patients. Mononuclerar cells were generally similar to controls with the exception of CD8⁺HLA-DR⁺ counts resembling Hb SS, Hematologic changes in Hb SC are limited to moderate granulocytosis in children and aduts, mild monocytosis in aduts, and increased activation of just one lymphocyte subset among those measured.     

Production of Murine Monoclonal Antibody to Fetal Hemoglobin

Fetal hemoglobin (Hb F) is a major hemoglobin (Hb) component at birth. Hb F levels are markedly elevated in a number of inherited and acquired disorders. Measurement of Hb F levels is usually carried out by alkali denaturation which is not very accurate for low and high values. An accurate estimation of Hb F, and also of F cells, is desired in many hematological disorders like sickle cell disease, in monitoring the efficacy of hydroxyurea (HU) therapy, to assess feto‐maternal hemorrhage (FMH) during pregnancy and in the postpartum period. We have raised a murine monoclonal antibody to human Hb F, that accurately measures the number of F cells by flow cytometry. The antibody was found to be potent and specific for F cells.     

糖化血红蛋白筛查在妊娠期糖尿病中的临床应用

目的讨论糖化血红蛋白筛查在妊娠期糖尿病中的临床应用价值。方法现将2019年7月—2020年7月期间将某妇产科医院产检的144例孕妇为该次研究对象,将其中患有妊娠糖尿病的72例孕妇归纳为实验组,将健康妊娠未患有妊娠糖尿病的72名孕妇作为对照组,比较两组孕妇糖化血红蛋白(HbA1c)和空腹血糖(FPG)水平以及HbA1c阳性检出率。结果①实验组检测糖化血红蛋白为(12.62±3.27)%,对照组检测糖化血红蛋白为(5.01±0.84)%,实验组检测空腹血糖为(6.75±0.42)mmol/L,对照组检测空腹血糖为(4.26±0.47)mmol/L,实验组孕妇的HbA1c和FPG水平与对照组相比明显较高,组间数据差异有统计学意义(t=19.126、33.520,P<0.001)。②实验组孕妇的HbA1c阳性检出率为27.70%,与对照组的11.11%相比明显较高,且组间差异有统计学意义(χ²=6.384,P<0.05);对照组孕妇的FPG阳性检出率为25.0%,与对照组的2.8%相比明显较高,且组间差异有统计学意义(χ²=14.864,P<0.001)。结论糖化血红蛋白筛查在妊娠期糖尿病中具有较高的应用价值,其可以尽早发现妊娠期糖尿病,提高妊娠糖尿病的诊断率,临床应用效果较好。     

糖化血红蛋白测定对妊娠期糖尿病的诊断价值研究

目的探究妊娠期糖尿病孕妇接受糖化血红蛋白检测的诊断价值。方法从2018年1月—2019年12月,该文将该院接收的29例妊娠期糖尿病孕妇与29名正常妊娠期孕妇选为观察组与对照组,均接受糖化血红蛋白测定,对比孕妇的血糖水平与糖化血红蛋白水平差异;统计血糖、糖化血红指标的敏感度与特异度差异;对比孕妇组间并发症差异。结果观察组孕妇空腹血糖(8.21±1.89)mmol/L、1 h血糖(12.32±3.18)mmol/L、2 h血糖(9.87±1.96)mmol/L、3 h血糖(8.08±1.77)mmol/L、糖化血红蛋白(7.76±2.46)%,均高于对照组,差异有统计学意义(t=11.111、7.055、11.778、10.280、6.613,P<0.05)。HbA1c的灵敏度与特异度分别为83.41%与89.63%,均高于空腹血糖与餐后2 h血糖,差异有统计学意义(χ²=8.124、6.412,P<0.05)。观察组孕妇发生妊高症、羊水过多等并发症12例,发生率41.38%,多于对照组,差异有统计学意义(P<0.05)。结论糖化血红蛋白测定对妊娠期糖尿病诊断价值较高,可为妊娠期糖尿病孕妇提供诊断与治疗依据。     

Laboratory Advances in Hemoglobin A1c Measurement: A Review of Variant Hemoglobins Interfering with Hemoglobin A1c Measurement

Hemoglobin A1c (HbA1c) is used routinely to monitor long-term glycemic control in people with diabetes mellitus, as HbA1c is related directly to risks for diabetic complications. The accuracy of HbA1c methods can be affected adversely by the presence of hemoglobin (Hb) variants or elevated levels of fetal hemoglobin (HbF). The effect of each variant or elevated HbF must be examined with each specific method.The most common Hb variants worldwide are HbS, HbE, HbC, and HbD. All of these Hb variants have single amino acid substitutions in the Hb β chain. HbF is the major hemoglobin during intrauterine life; by the end of the first year, HbF falls to values close to adult levels of approximately 1%. However, elevated HbF levels can occur in certain pathologic conditions or with hereditary persistence of fetal hemoglobin. In a series of publications over the past several years, the effects of these four most common Hb variants and elevated HbF have been described.There are clinically significant interferences with some methods for each of these variants. A summary is given showing which methods are affected by the presence of the heterozygous variants S, E, C, and D and elevated HbF. Methods are divided by type (immunoassay, ion-exchange high-performance liquid chromatography, boronate affinity, other) with an indication of whether the result is artificially increased or decreased by the presence of a Hb variant. Laboratorians should be aware of the limitations of their method with respect to these interferences.     

Clinical Advances in Hemoglobin A1c Measurement: Do Race and Ethnicity Impact Hemoglobin A1c Independent of Glycemia?

Hemoglobin A1c (HbA1c) is widely used as an index of mean glycemia, a measure of risk for the development of diabetes complications, and a measure of the quality of diabetes care. Emerging literature suggests that, although HbA1c levels change little over time within persons without diabetes, they vary considerably among individuals, suggesting that factors other than glycemia may impact HbA1c. Racial and ethnic differences in HbA1c have been described that do not appear to be explained by differences in glycemia. It is imperative that the nonglycemic factors that affect HbA1c be more clearly defined. Even more important, it must be determined whether differences among individuals or groups correlate with susceptibility to complications or merely reflect variation in hemoglobin glycation.     

Hemoglobin Variant Profiles among Brazilian Quilombola Communities

Brazilian Quilombolas are communities composed of African-derived populations that have their territories guaranteed by the Brazilian Constitution. The present study investigated the hemoglobin (Hb) variants among these population groups. This study was conducted in a total of 2843 individuals of Brazilian Quilombola communities of the Bahia, Pará, and Piauí states. All the participants had their Hb profiles evaluated. The Hb S (HBB: c.20A>T) variant was described in all the studied localities. However, the individuals in Bahia State had the highest frequency of the Hb C (HBB: c.19G>A) variant; individuals from Piauí State had a higher frequency of the Hb D-Punjab (HBB: c.364G>C) variant compared to the other states, and individuals from Pará State only carried the Hb S variant. The present study revealed a specific distribution of Hb variants that could represent different waves of African influence in these Brazilian populations.     

Hemoglobin Villejuif [beta 123(H1) Thr----Ile]: a new variant found in coincidence with polycythemia vera

A new abnormal hemoglobin, Hb Villejuif [beta 123(H1) Thr----Ile] has been discovered during the exploration of a polycythemia in a 87-year-old patient of French origin. The isoelectric focusing of the lysate revealed the presence of a variant hemoglobin with an isoelectric point very close to that of HbA. The oxygen binding properties of the patient's red blood cells being normal, it was clear that the polycythemia was not a consequence of the presence of this hemoglobin. In fact, the red blood cell morphology and the involvement of the other blood cell lines, demonstrating excessive hemopoiesis, led to the diagnosis of polycythemia vera.     

糖尿病患者糖化血红蛋白检测结果及意义探析

目的探讨糖尿病患者糖化血红蛋白检测结果及意义。方法选择该院2019年1—12月收治的79例糖尿病患者作研究组,选择同期79名健康人群作对照组,对比两组糖化血红蛋白检查结果,了解研究组当中糖化血红蛋白和空腹血糖的比例、糖化血红蛋白和并发症发生的关系。结果①研究组空腹血糖、餐后2 h血糖、糖化血红蛋白均高于对照组,差异有统计学意义(P<0.05)。②在研究组中,空腹血糖与糖化血红蛋白的关系:血糖<6.1 mmol/L的3例患者中,糖化血红蛋白异常仅1例(33.33%),血糖浓度在6.1~7.0 mmol/L的9例患者中,糖化血红蛋白异常5例(55.56%)。67例血糖>7.0 mmol/L的患者中,糖化血红蛋白异常67例,占100.00%。③在研究组中,糖化血红蛋白与并发症的关系:检测水平<6.5%的9例患者中1例出现并发症,发生率为11.11%;检测水平在6.5%~9%之间的31例患者并发症发生有14例,发生率为45.16%;检测水平大于9%的39例患者并发症有26例,发生率为66.67%,提示随着糖化血红蛋白水平的升高,糖尿病患者并发症的发生率明显增加(P<0.05)。结论糖化血红蛋白筛查和诊断糖尿病的应用价值显著,可以客观提供患者血糖相关的信息,且和并发症之间呈正相关,可帮助临床糖尿病患者治疗管理,值得临床推广使用。