Hemoglobin variants detected by hemoglobin A1c (HbA1c) analysis and the effects on HbA1c measurements

Background:

Hemoglobin (Hb) A1c is a tool widely used to monitor long-term glycemic control in diabetic patients. The objective of our study is to compare the HbA1c values measured on high performance liquid chromatography (HPLC) and immunoassay in patients who were detected to have hemoglobin variant after HbA1c analysis.

Materials and Methods:

We compared the HbA1c values measured using the Arkray Adams A1c HA-8160 (HPLC method) and Roche Cobas Integra (immunoturbidimetric method) from diabetic patients who were diagnosed with hemoglobin variants.

Results:

Forty-three diabetic patients were diagnosed with hemoglobin variants: 13 elevated Hb F, 12 Hb E trait, seven Hb S trait, seven Hb D trait, two Hb E / beta-Thalassemia, one Hb C trait, and one homozygous Hb S.

Conclusion:

Knowledge of hemoglobin variants affecting HbA1c measurements is essential, in order to avoid mismanagement of diabetic patients.     

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.     

HbA1c对糖尿病诊断价值的探讨

目的探讨HbA1c作为糖尿病诊断标准的临床应用价值。方法对43例个体行75gOGTT和Hb1c检测。结果HbA1c≥6．0％和≥6．5％分别作为诊断糖调节异常和糖尿病的标准,其灵敏度分别为70．59％和50．00％,特异度为88．89％和77．78％。结论以HbA0c≥6．0％作为糖调节异常的诊断标准具有较好的临床应用价值,但以HbA。c≥6．5％作为糖尿病诊断标准的应用价值并不满意。     

酶法测定HbA1c浓度的临床应用

目的 探讨酶法测定HbA1c浓度的临床应用价值.方法 根据定值高低值质控物的检测结果来评价酶法测定HbA1c的稳定性,用酶法测定31例糖尿病患者、68例非糖尿病对照者的HbA1c浓度,将结果与高效液相色谱(HPLC)法测得的结果进行比较和分析.结果 酶法的批内CV为0.93% (低值)、0.55%(高值),批间CV为1.43% (低值)、1.03%(高值);与HPLC法相关性系数r分别为0.967(n=31,P<0.01)、0.954(n=68,P<0.01).结论 酶法测定HbA1c可在全自动生化分析仪上进行,且具有简便、快速、易于推广等优点.     

False hemoglobin A1c value as a result of compound heterozygotes of hemoglobin E and hemoglobin New York

The presence of hemoglobin (Hb) variants might interfere with some glycated hemoglobin (HbA_1c) measurements. There have been a few reports of compound Hb variants affecting HbA_1c testing. Here, we report a case of the coinheritance of two Hb variants in the β‐globin gene. High‐performance liquid chromatography with the Hb program showed a high HbA₂ level. Similarly, an E‐window peak was separated on the high‐performance liquid chromatography with a glycated Hb program. However, capillary electrophoresis showed two abnormal peaks and no HbA peak. Sanger sequencing confirmed the presence of Hb New York and HbE. This is the first report of a compound heterozygote for HbE and Hb New York. The double heterozygote caused erroneous results for HbA_1c on high‐performance liquid chromatography and enzyme assay.     

The relationship of postprandial glucose to HbA1c

The gold standard for the assessment of the overall glycemic control is the determination of HbA1c. There are, however, insufficient data to determine reliably the relative contribution of fasting and postprandial plasma glucose to HbA1c. Increasing evidence suggests that excessive excursions of postprandial glucose might be important for the development of micro- and macroangiopathic complications. With respect to the treatment options, one important question to be answered is whether premeal, postmeal or fasting plasma glucose, alone or in combination, will be necessary in adjusting the therapy to achieve optimal HbA1c levels while minimizing hypoglycemia. HbA1c is difficult to predict from fasting plasma glucose. There are indications that there is a shift in the relative contribution from postprandial glucose at good to fair HbA1c levels (<7.3% to <9.2%) to fasting plasma glucose at high HbA1c (>9.3%). There is also a better correlation of afternoon and evening plasma glucose with HbA1c than with prebreakfast and prelunch plasma glucose values. Since the definition on how to define postprandial glucose is still a matter of debate and since postprandial glucose depends on the premeal blood glucose level and, on the time of the meal, its size and composition and the therapeutic strategy, the data so far available are inconclusive and the best correlation of HbA1c is with the area under the glucose profiles. Continuous glucose monitoring under daily life conditions will be the key to definitely unravel the relationship among HbA1c and fasting, premeal, postprandial and postabsorptive plasma glucose.     

Falsely high glycated haemoglobin [HbA1C] because of haemoglobin OSU-Christiansborg

Glycated haemoglobin (HbA1c) is routinely used to assess the degree of glycaemic control in diabetic patients. We report a case of a 73 year old diabetic woman who had an elevated HbA1c of 13.4%. She was on maximum oral hypoglycaemic agents and was commenced on insulin. However, her HbA1c continued to remain high at 20.4%. Subsequent tests revealed that she had a haemoglobin variant, Haemoglobin Osu-Christiansborg, causing the falsely high glycated haemoglobin.     

Accuracy and Precision of a Point-of-Care HbA1c Test

Background:Point-of-care (POC) hemoglobin A1c (HbA1c) testing has advantages over laboratory testing, but some questions have remained regarding the accuracy and precision of these methods. The accuracy and the precision of the POC Afinion™ HbA1c Dx test were investigated.Methods:Samples spanning the assay range were collected from prospectively enrolled subjects at three clinical sites. The accuracy of the POC test using fingerstick and venous whole blood samples was estimated via correlation and bias with respect to values obtained by an NGSP secondary reference laboratory (SRL). The precision of the POC test using fingerstick samples was estimated from duplicate results by calculating the coefficient of variation (CV) and standard deviation (SD), and separated into its components using analysis of variance (ANOVA). The precision of the POC test using venous blood was evaluated from samples run in four replicates on each of three test cartridge lots, twice per day for 10 consecutive days. The SD and CV by study site and overall were calculated.Results:Across the assay range, POC test results from fingerstick and venous whole blood samples were highly correlated with results from the NGSP SRL (r = .99). The mean bias was −0.021% HbA1c (−0.346% relative) using fingerstick samples and −0.005% HbA1c (−0.093% relative) using venous samples. Imprecision ranged from 0.62% to 1.93% CV for fingerstick samples and 1.11% to 1.69% CV for venous samples.Conclusions:The results indicate that the POC test evaluated here is accurate and precise using both fingerstick and venous whole blood.     

Hb Ube-2 in a diabetic case with an abnormally low HbA1C value.

A 69-year-old male diabetic patient had an abnormally low HbA1C value of 2.8%, which was inconsistent with his elevated fasting plasma glucose of 8.2 mmol/l. Hb analysis disclosed that the abnormal Hb was Hb Ube-2 [alpha68 (E17) Asn --> Asp] and it accounted for 21.5% of the total Hb. Since the glycated abnormal Hb emerged at the same position as did HbF on high performance liquid chromatography, the HbA1C value was falsely low. The present case demonstrates that Hb Ube-2 is one of the abnormal Hbs in which caution should be exercised when monitoring diabetic control.     

Reference ranges of glycated hemoglobin (HbA1c) in capillary blood in the Spanish population

Cross-sectional analysis describing HbA1c reference values by sex and age in a randomly selected Mediterranean general population sample. Using two methods, Point-of-Care systems and centralized laboratory, results show that HbA1c values increase with age. Almost half of the sample aged 65 years or older had median values >5.7% (prediabetes cut-off point).     

三种检测方法对变异血红蛋白患者糖化血红蛋白测定结果比较分析

目的 研究3种糖化血红蛋白（HbA1c）检测方法对变异血红蛋白患者HbA1c测定结果的比较分析.方法 收集2012年1月到2012年12月50例不同类型变异血红蛋白患者血样标本为研究对象,血红蛋白D、Q、G、J和E标本共25例,平均年龄（24±3）岁,男14例,女11例;血红蛋白F标本来源于新生儿,共25例,男11例,女14例;同时收集50例无变异血红蛋白标本为对照组,平均年龄（25±5）岁,男25例,女25例.使用亲和层析高效液相色谱（HPLC）法、离子交换HPLC法和免疫法三种方法检测HbA1c.用方差分析和Pearson相关分析法进行数据统计.结果 HbA1c结构正常组使用亲和层析HPLC法Ultra2、离子交换HPLC G8和VariantⅡ、免疫法DCA Vantage四种方法检测HbA1c分别为5.7％±1.1％、5.7％±1.2％、5.7％±1.2％、5.7％±1.1％,各组差异无统计学意义（F=0.023,P＞0.05）.25例变异血红蛋白F新生儿中,离子交换HPLC法和免疫法均检测不到血红蛋白F中的HbAlc值;空腹血糖与Ultra2检测HbA1c相关（r=0.647,P＜0.05）;空腹血糖与VariantⅡ和G8及DCA Vantage组的检测结果均无明显相关.亲和层析HPLC法不受血红蛋白D、Q、G、J和E的干扰,与血糖明显相关（r=0.823,P＜0.05）.离子交换HPLC法检测结果受到血红蛋白D、Q、G、J和E不同程度的干扰;免疫法测定的HbAlc与血糖相关（r=0.611,P＜0.05）.结论 亲和层析HPLC法测定的HbAlc可更准确地反映平均血糖水平.变异血红蛋白会干扰离子交换HPLC法的HbA1c的检测结果,免疫法检测结果仅受血红蛋白F的干扰.     

糖化血红蛋白用于筛查糖尿病的意义

目的比较并评价空腹血糖（FPG）和糖化血红蛋白（HbA1c）在筛查DM中的应用价值。方法上海地区研究对象2298名,为明确DM诊断而就诊者和DM高危人群接受DM筛查者,男956名,女1342名,年龄52±13岁,行OGTT并测定HbA1C;以其工作特征曲线（ROC）评价FPG和HbA。C在筛查DM中的敏感性和特异性。结果（1）按照1999年WHO的DM诊断标准,本研究人群糖耐量正常（NGT）、空腹血糖受损（IFG）、糖耐量受损（IGT）、IGT合并IFG和DM者分别为830、110、380、183、795例。其中DM患病率为34．6％。（2）依据ROC判断,与DM状态相关的FPG最佳临界点为6．1mmol／L,敏感性和特异性均为81．5％,曲线下面积为0．899（95％CI0．885～0．914）,阳性似然比4．18,阴性似然比0．23;与DM状态相关的HbA1c最佳临界点为6．1％,敏感性和特异性均为81．0％,曲线下面积为0．890（95％CI0．876-0．904）,阳性似然比4．26,阴性似然比0．23;如应用FPG≥6．1mmol／L或HbA1c≥6．1％筛查DM,敏感性和特异性分别为96．5％和65．2％,阳性似然比2．77,阴性似然比0．05。结论FPG和HbA1C在筛查DM中具有相似的价值,二者均有相似的特异性和敏感性以及阳性似然比和阴性似然比。为了最大限度的筛查出DM患者,建议对于6．1mmol／L≤FPG〈7．0mmol／L或HbA1c≥6．1％的患者行OGTT检查以明确有无DM。     

Predictive value of HbA1c level for in-hospital acute coronary syndrome patients with diabetes

Background Diabetes mellitus (DM) is the major risk factor of coronary artery disease (CAD), and the control status of blood sugar has direct effect on the prognosis of CAD. HbA1c is the important parameter reflecting control status of blood sugar, however, it is unclear about the value of in-hospital HbA1c in patients with acute coronary syndrome (ACS). Methods A retrospective analysis was performed for 236 in-hospital diabetic patients with ACS. Patients were stratified into two groups according to HbA1c level when admission (Well controlled group (HbA1c≤7.0%) and High HbA1c group (HbA1c > 7.0% ); major adverse cardiovascular events (MACE) group and Non-MACE group). In-hospital MACE and mortality were set as the observation target. Results 282 patients (112 in Well controlled group and 170 in High HbA1c group) were enrolled, of which 146 (51.77%), 63 (23.34%), and 73 (25.89%) patients respectively had unstable angina (UA), non-ST-segment elevation myocardial infarction (NSTEMI), and ST-segment elevation myocardial infarction (STEMI). Inhospital all-cause mortality and in-hospital MACE were both similar in Well controlled group and High HbA1c group (6.25% vs. 7.06% and 15.18% vs. 16.47%, P > 0.05). In MACEs, cardiac death (4.46% vs. 5.29%), recurrent myocardial infarction (2.68% vs. 2.94%), hemorrhage events (5.35% vs. 5.29%), malignant arrhyth- mia (6.25% vs. 5.29%), cardiac shock (4.46% vs. 4.12%), acute heart failure (8.93% vs. 10.0%), revascularization (4.46% vs. 5.29%) were also all similar in both two groups. In addition, there were no significant difference in HbA1c level between MACE group and Non-MACE group. Single-factor logistic regression analysis showed that HbA1c was not a risk factor for in-hospital MACE (P > 0.05) 1 . Conclusion The present study sug-gests that admission HbA1c is not the risk factor of in-hospital MACE in ACS patients with diabetes.