A case of a novel hemoglobin variant, Hb A2-Karatsu, discovered following a falsely elevated HbA1c value

Clin Chim Acta. 2022 Dec 1:537:154-157. doi: 10.1016/j.cca.2022.10.015. Epub 2022 Oct 22.

Abstract

The patient, a man in his thirties, presented to our hospital for a secondary examination after a 2020 medical check-up found a high hemoglobin A1c (HbA1c) level on high-performance liquid chromatography (HPLC). The HbA1c level determined by HPLC (HA-8180V, fast mode) was elevated at 6.8%, but a 75-g glucose tolerance test showed normal glucose tolerance. The glycated albumin level was within the reference range at 14.6%. The continuous glucose monitoring-derived mean blood glucose and the percentage of time in range were 99 mg/dL and 98%, respectively. The HbA1c levels determined by HPLC (G9, fast mode), enzymatic assay, and immunoassay were all 5.3%. An isoelectric focusing analysis showed an abnormal band on the anode side of HbA2, and a globin gene analysis detected a heterozygous mutation at codon 144 [AAG (Lys) → TAG (stop codon)] in the δ-chain. Since this mutation is a novel δ-chain hemoglobin variant, it was given the name 'Hb A2-Karatsu'.

Keywords: Delta chain; Glycated albumin; Hb A2-Karatsu; Hemoglobin A1c; Hemoglobin variant.

Publication types

  • Case Reports

MeSH terms

  • Blood Glucose
  • Blood Glucose Self-Monitoring*
  • Chromatography, High Pressure Liquid
  • Glucose Tolerance Test
  • Glycated Hemoglobin / analysis
  • Hematologic Tests
  • Hemoglobins, Abnormal* / analysis
  • Hemoglobins, Abnormal* / genetics
  • Humans
  • Male

Substances

  • Glycated Hemoglobin A
  • Blood Glucose
  • Hemoglobins, Abnormal