Hb Yongning [β1 (NA1) Val→Leu; <i>HBB</i> :C.4G &gt; C]: A Novel Hemoglobin Variant Causing Significant Interference in Common Glycated Hemoglobin Assays

We report a novel β-globin chain variant identified in a proband who is also a carrier of β-thalassemia. Glycated hemoglobin analysis revealed an elevated Hb A_1c level of 20.34% using high-performance liquid chromatography (HPLC), while the fasting blood glucose level was 5.49 mmol/L. Subsequent testing using an alternative HPLC system showed an Hb A_1c value of 2.8%, and the immunoturbidimetric assay failed to yield a detectable result. Sanger sequencing confirmed the presence of two heterozygous point mutations in the β-globin gene: CD1 (GTG > CTG) (<i>HBB</i>:c.4G > C) and CD17 (AAG > TAG) (<i>HBB</i>:c.52A > T). Hemoglobin analysis showed the variant electrophoresing at the HbA position. The <i>HBB</i>:c.4G > C mutation represents a previously unreported variant, which has been designated Hb Yongning based on the proband's geographical origin.