Hb Kalundborg [beta 79(EF3)Asp -> Glu; HBB: c.240C>a], a Possible Low-affinity Hemoglobin Variant Detected during Hb A(1c) Measurement

A previously unknown hemoglobin (Hb) variant was detected during measurement of glycosylated Hb (Hb A(1c)) after the introduction of a new high performance liquid chromatography (HPLC) apparatus. Subsequent DNA sequencing revealed a heterozygous single nucleotide substitution at codon 79 (C>A) on the beta-globin gene changing an amino acid [beta 79(EF3)Asp -> Glu; HBB: c.240C>A]. The new Hb variant was named Hb Kalundborg after the place of origin of the proband. Heterozygosity for this mutation appears to have no clinical significance in itself except for a possibly slightly lower oxygen affinity. However, it interferes with Hb A(1c) measurement by HPLC, causing a falsely high Hb A(1c) concentration when using the G11 apparatus with clinical implications possibly to follow.