Quantification of glycated hemoglobin by electrospray ionization mass spectrometry

Glycated hemoglobin, considered to be the best index for the treatment of diabetes mellitus, was measured by electrospray ionization mass spectrometry (ESI/MS) according to the method proposed by Morris et al. at the 44th ASMS Conference on Mass Spectrometry and Allied Topics, 1996. They compared the values obtained by MS and affinity chromatography. Here, the values obtained by ESI/MS were compared with those obtained by high-performance liquid chromatography and by latex agglutination immunoassay. Whole blood samples were diluted 500 fold with 0.2% formic acid-50% acetonitrile solution and 5 microliters of the diluted solution was injected with the ESI/MS system (TSQ 7000) via a sample loop. The within-run and between-run relative standard deviations of the ratio of glycated and non-glycated beta-chain were less than 5%. The correlation coefficients between ESI/MS and conventional methods were higher than 0.96. However, considerable discrepancies were observed among methods. ESI/MS will allow reproducible measurements of glycated hemoglobin and will be useful in the quality control of HbA1c measurement by other principles and also in routine clinical laboratory tests.