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

UNASSIGNED: Hemoglobin A1c has been widely used to diagnose and monitor diabetes. However, the accuracy of HbA1c analysis can be significantly affected by hemoglobin variants, leading to falsely low or elevated levels and misdiagnosis or inappropriate diabetes management.
UNASSIGNED: In this study, we present the case of a 23-year-old man with undetectable HbA1c levels during his annual checkup by high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE). To investigate the reason for HbA1c absence, Sanger sequencing, multiplex ligation-dependent probe amplification assay (MLPA), long-read single molecule real-time sequencing (SMRT) and MALDI-TOF mass spectrometry (MS) were performed, and the proband was identified as compound heterozygous of β-thalassemia with Hb G-Taipei (HBB:c.68A > G) and Hb Lepore-Boston-Washington (NG_000007.3:g.63632_71046del).
UNASSIGNED: The combination of these molecular technologies including MLPA, long-read SMRT sequencing and MALDI-TOF MS is beneficial for identifying rare hemoglobin variants. This case also provides essential evidence for uncovering the effect of compound heterozygosity for Hb Lepore-Boston-Washington and Hb G-Taipei on hematological phenotypes and HbA1c analysis.

UNASSIGNED: In clinical practice, the majority of α-thalassaemia cases arise from deletions of the α-globin genes. However, a subset of cases is attributed to rare haemoglobin variants, which can manifest with borderline or normal screening results, potentially leading to missed diagnoses in clinical practice.
UNASSIGNED: Blood samples were collected from family members and underwent haematological, DNA and RNA analysis.
UNASSIGNED: The five-month-old proband presented a haematological phenotype consistent with Hb H disease. The mother\'s haematology profile was consistent with an α-thalassaemia carrier, while the father exhibited a borderline reduction in MCV and MCH. MALDI-TOF identified an abnormal α-chain in the proband. DNA analysis revealed a novel α-globin variant (HBA2:c.175C>A, α58His>Asn, Hb DG-Nancheng) affecting the distal histidine in the family. The father and the mother had α-genotype of --SEA/αα and αDG-Nanchengα/αα, respectively; while the proband inherited both mutant alleles (--SEA/αDG-Nanchengα). Sequencing of cDNA from HBA2 gene identified an equal ratio of normal and mutant alleles.
UNASSIGNED: This rare case highlighted the importance of identifying rare haemoglobin variant during prenatal screening. The clinical and genetic data provides useful information on the pathogenicity of this variant and further insight into the role of distal histidine residue of α-globin.

Hemoglobin (Hb) Chile [β28(B10) Leu > Met; HBB: c.85 C > A] is a rare hemoglobin variant caused by a missense mutation in the HBB gene. Only one case of Hb Chile has been reported worldwide so far. It is an unstable hemoglobin, characterized by cyanosis associated with chronic methemoglobinemia and hemolytic anemia induced by sulfonamides or methylene blue.
A 9-year-3-month-old girl had mild anemia of unknown etiology for more than 6 years. She had a slight pallor without other symptoms or signs. The complete blood count revealed normocytic normochromic anemia with a sometimes-elevated reticulocyte count, and the bone marrow cytology showed marked erythroid hyperplasia, but the tests related to hemolysis were normal. Therefore, the whole exome sequencing was performed and showed a heterozygous mutation for HBB: c.85 C > A. With asymptomatic methemoglobinemia confirmed later, she was eventually diagnosed with Hb Chile.
This is the first report of Hb Chile in China and the second worldwide. This case shows that Hb Chile is clinically heterogeneous and difficult to diagnose and expands our understanding on the clinical and hematological traits of the disease.

UNASSIGNED: To examine the common types of hemoglobin variants and to evaluate the influence of common variants on the results of two kinds of glycosylated hemoglobin (HbA1c) tests.
UNASSIGNED: We conducted a retrospective study, analyzing the data of a patient population undergoing two HbA1c tests, high performance liquid chromatography (HPLC) and capillary electrophoresis (CE), at West China Hospital, Sichuan University between March 2021 and February 2022. By screening the chromatograms, the hemoglobin variants were identified and their migration positions in the CE method were recorded. The effects of the variants with different migration positions on the findings of the two methods were compared. Variant samples with different migration positions were selected and Sanger sequencing was performed to determine mutations in HBA1, HBA2, and HBB genes in the variant samples.
UNASSIGNED: We examined the HbA1c of 207 786 patient samples, identifying variant peaks in the chromatograms of 372 patients. The detection rate of variants was 0.18%, with the variant identification rate of HPLC being 43.3% and that of CE, 100%. Through sequencing, 20 variants were detected. A total of 261 patient samples were tested for HbA1c with both HPLC and CE. HPLC reported all HbA1c results, while CE did not report HbA1c results for 28 samples, among which, 26 showed abnormal peaks that overlapped with HbA1c peaks, and 2 showed abnormal peaks that overlapped with HbA0 peaks. The commonly observed variant migration positions, as revealed by CE, were at the horizontal coordinates of 225±1, 200±3, 100±2, 124±1, 70±2, and 182±1. There was significant difference between HPLC method and CE method in the determination of HbA1c ( P<0.0083), and the difference between the two methods was the largest when there were variants in the 200±3 region. Linear regression showed that the correlation of HbA1c results between the two methods was different when different regional variants were present, and that the correlation between the two methods was strongest when 124±1 region was present ( r=0.998).
UNASSIGNED: There are diverse types of hemoglobin variants and most of them can affect the HbA1c findings of HPLC. Analyzing the chromatogram facilitates the identification of the variants.

BACKGROUND: Mutations in the hemoglobin subunit delta (HBD) gene (MIM#142000) are associated with decreased levels of the Hemoglobin A2 (Hb A2 ) fraction. We aimed to examine the prevalence of HBD gene mutations and summarize their characteristics in the Chinese population.
METHODS: Individuals who exhibited Hb A2 levels below 1.8%, with or without Hb A2 variant peaks, were chosen for further investigation. Hemoglobin analysis was conducted using capillary electrophoresis. Common α and β-thalassemia in China were detected using gap-PCR and reverse dot blot hybridization. The presence of HBD gene mutations was confirmed by DNA sequencing.
RESULTS: A total of 188 patients were identified as carriers of the HBD gene mutation, with a prevalence of approximately 0.46%. We discovered 36 types of mutations, 30 of which resulted in δ-globin variants, while the remaining 6 resulted in δ-thalassemia. The most common mutation was HBD:c.-127 T > C, accounting for 87.2% of δ-thalassemia cases. In addition, we identified 11 novel HBD gene mutations and found 10 cases compounded with other common thalassemias.
CONCLUSIONS: We observed a high prevalence of HBD gene mutations in southern China. Our findings provide a genetic basis for screening for δ-thalassemia and enrich the spectrum of HBD gene mutations.

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.

UNASSIGNED: Hb Chapel Hill [Alpha2 74(EF3) Asp > Gly] results from an GAC > GGC substitution at codon 74 of the HBA1 or HBA2 genes. Hb Chapel Hill has not been reported since 1986.
UNASSIGNED: A heterozygous mutation, HBA2: c.224A > G, was identified in the proband, her father and sister. We compared the haematological and clinical data of this family with the data reported in the limited number of individuals.
UNASSIGNED: Having excluded iron deficiency, the Hb Chapel Hill was asymptomatic in heterozygous state. The cases presented here characterize cases in new techniques including capillary electrophoresis (CE). Two aberrant peaks were identified by CE, a major peak migrating in the zone 7 that correspond to Hb Chapel Hill (αChapel Hill 2β2) and a minor peak migrating in the zone 1 that correspond to Hb Chapel Hill2 (αChapel Hill 2δ2). Focusing on the variant expression, the Hb Chapel Hill plus Hb A2 variant were around 18.9-20.6% of total Hb in three members.
UNASSIGNED: This data will be useful for providing up-to-date and high quality information on the Hb Chapel Hill.

UNASSIGNED: In the present study, two unrelated cases of Hb Q-Thailand heterozygosity unlinked with the (-α4.2/) α+-thalassemia deletion allele were identified by long-read single molecule real-time (SMRT) sequencing in southern China. The aim of this study was to report the hematological and molecular features as well as diagnostic aspects of the rare manifestation.
UNASSIGNED: Hematological parameters and hemoglobin analysis results were recorded. A suspension array system for routine thalassemia genetic analysis and long-read SMRT sequencing were applied in parallel for thalassemia genotyping. Traditional methods, including Sanger sequencing, multiplex gap-polymerase chain reaction (gap-PCR) and multiplex ligation-dependent probe amplification (MLPA), were used together to confirm the thalassemia variants.
UNASSIGNED: Long-read SMRT sequencing was used to diagnose two Hb Q-Thailand heterozygous patients for whom the hemoglobin variant was unlinked to the (-α4.2/) allele for the first time. The hitherto undescribed genotypes were verified by traditional methods. Hematological parameters were compared with those of Hb Q-Thailand heterozygosity linked with the (-α4.2/) deletion allele in our study. For the positive control samples, long-read SMRT sequencing revealed a linkage relationship between the Hb Q-Thailand allele and the (-α4.2/) deletion allele.
UNASSIGNED: Identification of the two patients confirms that the linkage relationship between the Hb Q-Thailand allele and the (-α4.2/) deletion allele is a common possibility but not a certainty. Remarkably, as it is superior to traditional methods, SMRT technology may eventually serve as a more comprehensive and precise method that holds promising prospects in clinical practice, especially for rare variants.

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.