BACKGROUND: Hb Himeji is variant hemoglobin associated with increased glycation in a mutated β chain. We measured HbA1c using various methods in a family with Hb Himeji. METHODS: The proband was a 42-y female. While receiving treatment for Graves' disease, an oral glucose tolerance test showed normal glucose tolerance, but HbA1c by enzymatic assay was abnormally elevated (11.6%). Hemoglobin gene analysis identified Hb Himeji [β140 (H18) Ala→Asp]. RESULTS: HbA1c values measured by high-performance liquid chromatography (HPLC; HLC-723G8 and HA-8160 instruments), immunoassay, enzymatic assay, affinity method, and electrospray ionization/mass spectrometry were 3.2%, 5.2%, 11.5%, 9.7%, 7.2%, and 9.6%, respectively. Glycation product of the variant hemoglobin measured by HPLC, using HLC-723G8 and HA-8160, was 9.1% and 4.5%, respectively. The proband's father with type 2 diabetes was the first reported case of Hb Himeji. HbA1c by affinity method was markedly elevated (18.0%), but it was 5.3% by HPLC. The proband's two sisters also had Hb Himeji variant and similar method-dependent discrepancies in HbA1c values were observed. CONCLUSIONS: In the patients with Hb Himeji, discrepancies occur between plasma glucose and HbA1c with all measurement methods because of differences in HPLC mobility, increased glycation, and antigenic changes of the variant β chain.
BACKGROUND: Hb Himeji is variant hemoglobin associated with increased glycation in a mutated β chain. We measured HbA1c using various methods in a family with Hb Himeji. METHODS: The proband was a 42-y female. While receiving treatment for Graves' disease, an oral glucose tolerance test showed normal glucose tolerance, but HbA1c by enzymatic assay was abnormally elevated (11.6%). Hemoglobin gene analysis identified Hb Himeji [β140 (H18) Ala→Asp]. RESULTS: HbA1c values measured by high-performance liquid chromatography (HPLC; HLC-723G8 and HA-8160 instruments), immunoassay, enzymatic assay, affinity method, and electrospray ionization/mass spectrometry were 3.2%, 5.2%, 11.5%, 9.7%, 7.2%, and 9.6%, respectively. Glycation product of the variant hemoglobin measured by HPLC, using HLC-723G8 and HA-8160, was 9.1% and 4.5%, respectively. The proband's father with type 2 diabetes was the first reported case of Hb Himeji. HbA1c by affinity method was markedly elevated (18.0%), but it was 5.3% by HPLC. The proband's two sisters also had Hb Himeji variant and similar method-dependent discrepancies in HbA1c values were observed. CONCLUSIONS: In the patients with Hb Himeji, discrepancies occur between plasma glucose and HbA1c with all measurement methods because of differences in HPLC mobility, increased glycation, and antigenic changes of the variant β chain.
Authors: Vânia Guedes; Rita Bettencourt-Silva; Joana Queirós; Maria da Luz Esteves; Maria José Teles; Davide Carvalho Journal: J Med Case Rep Date: 2017-07-26