Fetal hemoglobin: assessment of glycation and acetylation status by electrospray ionization mass spectrometry

Abstract

Electrospray ionization mass spectrometry (ESI-MS) can be used for the measurement of glycated adult hemoglobin. Here, we describe the evaluation of ESI-MS for measurement of glycated (GHbF) and acetylated (AcHbF) fetal hemoglobin and the identification by mass of different chains of fetal hemoglobin. Blood samples were diluted in an acidic denaturing solvent, desalted with AG 50W-X8 resin and introduced directly into the mass spectrometer. Resulting mass spectra were processed to determine the percentage of GHbF and AcHbF and the gamma-chain masses. The procedure yielded reproducible quantitative assay of GHbF and AcHbF, with coefficients of variation <4.9%. Measurement of alpha-chain glycation was similarly reproducible and is suggested as an alternative marker of glycemic control. Marked increases in glycation occurred in dried spot blood samples, which were related to duration of storage, temperature and glucose concentration. Molecular masses of fetal hemoglobin chains were also determined and in 42 neonates studied, two types A and B were identified, two-thirds were type A with gamma-chain masses corresponding to (G)gamma and (A)gamma. In type B, the relative abundance of the (A)gamma-chain was less and the apparent intensity of the (G)gamma-chain was higher. ESI-MS can be used for the estimation of GHbF and AcHbF and the accurate measurement of fetal gamma-chain masses. The use of whole blood is preferred for analysis.