The survey of abnormal hemoglobins in the Kobe district: Hb G-Coushatta [beta 22(B4)Glu----Ala], Hb Ankara (beta 10(A7)Ala----Asp], Hb Handa [alpha 90(FG2)Lys----Met], and Hb J-Habana [alpha 71(E20)Ala----Glu]

Pathology consultation on HbA(1c) methods and interferences

OBJECTIVES

To review the various hemoglobin (Hb) A1c methods, with a focus on interferences resulting from Hb variants.

METHODS

HbA1c is a marker used for the diagnosis and management of diabetes. Each available HbA1c method has advantages and challenges, such as its susceptibility to interferences.

RESULTS

The presence of Hb variants and/or abnormalities in RBC turnover cannot only interfere analytically with HbA1c measurements but also may affect the clinical interpretation of HbA1c values.

CONCLUSIONS

Familiarity with the advantages and challenges of the various methods used for HbA1c testing is essential when establishing therapeutic management and goals based on HbA1c results, especially in populations with a high prevalence of Hb variants.

Further identification of Hb G-Coushatta [beta22(B4)Glu-->Ala (GAA-->GCA)] in Thailand by the polymerase chain reaction-single-strand conformation polymorphism technique and by amplification refractory mutation system-polymerase chain reaction

Thalassemias and hemoglobinopathies are very common among Southeast Asian populations, particularly in Thailand, where it is estimated that nearly 30% of the population carries at least one such disorder. Moreover, the heterogeneity of different mutant alpha- and beta-globin alleles contributes to the complexity in diagnosis and proper management, as more than 60 thalassemia syndromes and hemoglobinopathies have been described. Herein we report a further case of Hb G-Coushatta [beta22(B4)Glu-->Ala (GAA-->GCA)] (also known as G-Saskatoon, G-Hsin Chu and G-Taegu) in a Thai family in which the mother was found to have an unusual hemoglobin (Hb) anomaly in combination with Hb E [beta26(B8)Glu-->Lys, GAG-->AAG]. We applied our recently described polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique to scan the beta-globin genes and found an aberrant pattern in exon 1. The molecular analysis by direct genomic sequencing successfully identified the nucleotide mutation (codon 22, GAA-->GCA), and a novel amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) for this variant is described.

Genetic studies suggest a multicentric origin for Hb G-Coushatta [beta22(B4)Glu-->Ala]

Hb G-Coushatta [beta22(B4)Glu-->Ala] is found in geographically separated ethnic groups. Commonest along the Silk Road region of China but also present in the North American Coushatta, we sought to determine whether this variant had a unicentric or multicentric origin. We examined the haplotype of the beta-globin gene cluster in two Chinese families and in five Louisiana Coushatta heterozygous for this mutation. Chinese and Louisiana Coushatta had different haplotypes associated with the identical Hb G mutation. These haplotypes were defined by the presence of a HindIII restriction site in the Agamma-globin gene and AvaII restriction site in the beta-globin gene in Chinese subjects and their absence in the Louisiana Coushatta. We found a CAC at codon beta2 (beta-globin gene framework 1 or 2) linked to the Hb G-Coushatta gene in Chinese, and a CAT (framework 3) in Louisiana Coushatta, indicating different beta-globin gene frameworks. Both the Hb G-Coushatta mutation (GAA-->GCA) and the codon 2 CAC-->CAT polymorphism are normal delta-globin gene sequences, suggesting the possibility of gene conversion. We conclude that Hb G-Coushatta had at least two independent origins. This could be due to separate mutations at codon beta22 in Chinese and Louisiana Coushatta, a mutation at this codon and a beta-->delta conversion, or two beta-->delta gene conversion events.

Hb Fukutomi [alpha 126(H9)Asp----Val]: a new hemoglobin variant with high oxygen affinity

Hb Fukutomi [alpha 126(H9)Asp----Val], a new hemoglobin variant with a high affinity for oxygen (log P50 = 0.201 at pH 7.0, normal = 1.087) was detected in a Japanese male during a screening survey. The amino acid substitution is located in the alpha 1 beta 1 contact of the tetramic molecule. Like other variants of the high oxygen affinity type Hb Fukutomi showed increased resistance to auto-oxidation. The tryptic peptide alpha T-13, that usually forms part of the trypsin-resistant core of the alpha chain, was cleaved off by trypsin in the new variant and released into the soluble fraction.