Higher degree of glycation of hemoglobin S compared to hemoglobin A measured by mass spectrometry: Potential impact on HbA1c testing.
BACKGROUND
Glycated hemoglobin (GHb), reported as HbA1c, is used as marker of long-term glycemia for diabetic patients. HbA1c results from boronate affinity methods are generally considered to be unaffected by most hemoglobin variants; this assumes comparable glycation of variant and non-variant (HbAA) hemoglobins. In this report, glycation of HbA beta chain (βA) and HbS beta chain (βS) for the most common Hb variant trait (HbAS) are examined.


METHODS
We analyzed 41 blood samples from subjects with HbAS, both with and without diabetes. Using LC-MS, ratios of glycated HbS to glycated HbA were determined by comparison of areas under the curves from extracted ion chromatograms.


RESULTS
Glycation of βS chains was significantly higher (p<0.001) than βA chains; this difference was consistent across subjects. Total (α+β) glycated HbAS was theoretically estimated to be ~5% higher than glycated HbAA.


CONCLUSIONS
This novel mass-spectrometric approach described allows for relative quantification of glycated forms of βS and βA. Although βS glycation was significantly higher than that of βA, the difference in total glycation of HbAS versus HbAA was smaller and unlikely to impact clinical interpretation of boronate affinity HbA1c results. These data support the continued use of boronate affinity to measure HbA1c in patients with HbAS.
Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO, United States.
Kuanysh
K
Kabytaev
Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO, United States.
Shawn
S
Connolly
Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO, United States.
Curt L
CL
Rohlfing
Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States.
David B
DB
Sacks
Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO, United States. Electronic address: stoyanova@health.missouri.edu.
Alexander V
AV
Stoyanov
Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO, United States. Electronic address: littler@health.missouri.edu.
Randie R
RR
Little
D002853:Chromatography, Liquid; D006442:Glycated Hemoglobin / Q000032:analysis* / Q000737:chemistry; D006031:Glycosylation; D006441:Hemoglobin A / Q000737:chemistry*; D006451:Hemoglobin, Sickle / Q000737:chemistry*; D006801:Humans; D013058:Mass Spectrometry
D006442:Glycated Hemoglobin; D006441:Hemoglobin A; D006451:Hemoglobin, Sickle; C517652:hemoglobin A1c protein, human
Boronate affinity; Glycation sites; Hemoglobin A1c; Hemoglobin S; Hemoglobin glycation; Mass spectrometry