Impact of glutathione-HbA1c on HbA1c measurement in diabetes diagnosis via array isoelectric focusing, liquid chromatography, mass spectrometry and ELISA.

Hemoglobin A1c (HbA1c) has been proven to be a key biomarker for diabetes screening, and glutathiolation of HbA1c (viz., GSS-HbA1c) has been identified. However, the impact of GSS-HbA1c on the measurement of HbA1c for diabetes screening has not been quantitatively assessed yet. To address the issue, the micropreparative capillary isoelectric focusing (cIEF) developed in our previous work was used for the high resolution separation and purification of hemoglobin (Hb) species. The main fractions of HbA0, HbA3 and HbA1c extracted from the developed cIEF were identified by validated Mono S method. The proposed GSS-HbA1c fractions in the cIEF were pooled and identified by electrospray ionization mass spectrometry (ESI-MS). The HbA1c enzyme-linked immunosorbent assay (ELISA) kit was employed for further quantitative analysis of GSS-HbA1c. A total of 34 blood samples with HbA1c levels from 4.2% to 13.4% were assessed via the above comprehensive strategy of IEF-HPLC-MS-ELISA. It was demonstrated that the HbA1c levels detected by cation exchange LC were considerably influenced by the glutathiolation of Hb and the range of detected GSS-HbA1c values was between 0.23% and 0.74%. The results and developed cIEF methods have considerable significances for investigation of diabetes and clinical diagnosis.