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 HbA1c 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 HbA1c 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 HbA1c 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 HbA1c measurement by Variant II Turbo 2.0 and Bio-Rad D100. This study demonstrates that patients with abnormally high HbA1c levels should be highly suspected of carrying Hb variants. When the HbA1c results are considered unreliable, other indicators such as glycated albumin may be a possible alternative to HbA1c in diabetic patients.

[Analysis of L2HGDH gene mutation in a patient with 2-hydroxyglutaric aciduria].

OBJECTIVE: To explore pathogenic mutation in a family affected with 2-hydroxyglutaric aciduria. METHODS: Exons of 3 candidate genes, including L2HGDH, D2HGDH and SLC25A1, were amplified with polymerase chain reaction and subjected to direct sequencing. RESULTS: DNA sequencing has found that the proband and his affected younger brother have both carried a heterozygous mutation c.845G>A (p.R282Q) in the exon 7 of the L2HGDH gene. The same mutation was not detected in the his sister who was healthy. Pedigree analysis has confirmed that the above mutation was inherited from the mother. No mutation was detected in exons and flanking sequences of the D2HGDH and SLC25A1 genes. CONCLUSION: Mutation of the L2HGDH gene probably underlies the 2-hydroxyglutaric aciduria in this family.