title: Measurement of glycated albumin in serum and plasma by LC-MS/MS.
abstract: BACKGROUND
  Diagnosis of diabetes and monitoring of long-term blood sugar are preferably done by measurement of glycated hemoglobin (HbA1c). Diabetic patients with end stage renal disease (ESRD) may have short-lived red blood cells due to hemodialysis (HD), and thus higher turnover of hemoglobin. The level of glycated hemoglobin (HbA1c) may be lower than expected for these patients, even at increased blood glucose, possibly making glycated albumin (GA) measurement a better alternative.
  
  
  METHODS
  The percentage of GA was measured by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Fast and efficient trypsin digestion of proteins in diluted serum or plasma resulted in a high number of proteotypic peptides from albumin, including KQTALVELVK which was detected both glycated and non-glycated by multiple reaction monitoring (MRM). The percentage of GA was estimated by neat peak area response of glycated peptide divided by the sum of glycated and non-glycated peptide.
  
  
  RESULTS
  Acceptable method reproducibility (6% CV), repeatability (2-6% CV), limit of quantification (0.75% GA), linearity (R(2) = 0.999) and recovery (79 ± 9%) was achieved without using calibration or isotope-labeled internal standard. GA was strongly correlated with HbA1c (r = 0.84) for patients without ESRD. The average ratio of GA/HbA1c was significantly higher (p = 0.0021) for ESRD patients (1.84 ± 0.38, n = 62) compared to other patients (1.67 ± 0.28, n = 225).
  
  
  CONCLUSIONS
  GA measurement by detecting glycation in KQTALVELVK with LC-MS/MS seems to be a useful supplement to HbA1c for detecting increased blood glucose in diabetic patients with ESRD.
authors.affiliation: a Department of Medical Biochemistry , Stavanger University Hospital , Stavanger ;
authors.forename: Cato
authors.initials: C
authors.lastname: Brede
authors.affiliation: b Department of Mathematics and Natural Sciences , University of Stavanger , Stavanger , Norway.
authors.forename: Beate
authors.initials: B
authors.lastname: Hop
authors.affiliation: b Department of Mathematics and Natural Sciences , University of Stavanger , Stavanger , Norway.
authors.forename: Kåre
authors.initials: K
authors.lastname: Jørgensen
authors.affiliation: a Department of Medical Biochemistry , Stavanger University Hospital , Stavanger ;
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Skadberg
mesh_terms: D000595:Amino Acid Sequence; D001774:Blood Chemical Analysis; D002853:Chromatography, Liquid; D048909:Diabetes Complications / Q000097:blood*; D006442:Glycated Hemoglobin / Q000378:metabolism; D017127:Glycation End Products, Advanced; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000209:etiology; D012709:Serum Albumin / Q000378:metabolism*; D053719:Tandem Mass Spectrometry; D000093423:Glycated Serum Albumin
chemical_list: D006442:Glycated Hemoglobin; D017127:Glycation End Products, Advanced; D012709:Serum Albumin; D000093423:Glycated Serum Albumin; C517652:hemoglobin A1c protein, human
keywords: Blood glucose; diabetes; end stage renal disease; glycated albumin; liquid chromatography; mass spectrometry