Falsely high HbA1c value due to a novel α1-globin gene mutation: Hb shantou [α127(H10)Lys > Glu; HBA1: c.382 A > G]

Interference of hemoglobin variants in HbA1c quantification

Fasting blood glucose and glycated hemoglobin (HbA_1c) are routine biomarkers to screen and monitor diabetes mellitus. HbA_1c results from glycation at the N-terminus of the β globin chain of tetrameric human hemoglobin. Fasting blood glucose level varies with the nature and amount of food intake, physical exercise, etc., and, accordingly, is a short-term measure of glucose control. In contrast, HbA_1c provides an average measure of glucose control for the long-term (8-12 weeks). Unfortunately, genetic variants of hemoglobin may interfere with HbA_1c quantification using ion exchange chromatography, capillary electrophoresis, immunoassay and boronate affinity chromatography. Mass spectrometry, however, measures total glycation of hemoglobin across both α and β globin chains and correlates well with the ion exchange based method. Additionally, mass spectrometry based quantification is not impacted by the presence of genetic variants of hemoglobin and thus might be a better analytical choice for diabetes mellitus.

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.

Electrophoresis features and genotypes of Hb bart's hydrops fetalis

Hydrops fetalis syndrome (Hb Bart's disease) is one of the common fetal development abnormalities and the most severe form of α-thalassemia. It causes fetal death during the third trimester or shortly after birth. The aim of this study is to investigate the feature of Hb Bart's disease by Capillary electrophoresis (CE) and its genotypes. A total of 38 cases of suspected fetal Hb Bart's disease were analyzed by B-ultrasound and CE, including 17 with 24-28 weeks of pregnancy, 9 with 29-32 weeks of pregnancy, and 12 with 33-38 weeks of pregnancy. All cases were then identified by DNA analysis. The minimum concentration of Hb Bart's was 72.2% and the highest 90.9%. Hb Bart's fraction increased while that of Hb Portland decreased with the duration of pregnancy. In order to avoid serious maternal morbidity, it is necessary to diagnose Hb Bart's disease as soon as possible and CE can be used as a method of rapid diagnosis.