False HbA1cValue due to a Rare Variant of Hemoglobin J-Cubujuqui

Hemoglobin (Hb) J-Cubujuqui is a rare Hb variant, and reports about it are very limited. There are no descriptions that it affects the results of glycated Hb.

In this study, we describe a rare variant discovered during newborn screening. Both high-performance liquid chromatography (HPLC) and capillary electrophoresis for hemoglobin analysis displayed abnormal peaks. The Hb variant was confirmed by Sanger sequencing.

The pedigree study shows the variant was inherited from the newborn's father. His fasting blood glucose (FBG) level was 5.5 mmol/L. HbA1c measured by HPLC was falsely low in her father (2.41%), whereas that measured by immunoassay was normal (5.11%). Sanger sequencing revealed a heterozygous mutation (CGT˃AGT) at amino acid position 141 of the α1 gene, corresponding to Hb J-Cubujuqui [α1 141(HC3) Arg→Ser (CGT˃AGT); HBA1:c.424C˃A (or HBA2)].

This is the first report that Hb J-Cubujuqui interferes with the measurement of HbA1cand prompts clinicians to pay attention to the accuracy of glycated Hb results.