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

Background: 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.Methods: 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.Results: 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 alpha 1 gene, corresponding to Hb J-Cubujuqui [alpha 1 141(HC3) Arg -> Ser (CGT>AGT); HBA1:c.424C>A (or HBA2)].Conclusions: 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.