title: Preparation of highly purified monomeric human serum albumin as secondary reference material for standardization of urinary albumin immunoassays.
abstract: BACKGROUND
  International external quality assessments have shown variation in results of urinary albumin among various immunoassays. A well-defined candidate reference material for urine albumin (cRM-UA) was prepared to improve standardization.
  
  
  METHODS
  cRM-UA was prepared from a commercially available preparation of human serum albumin by using gel-filtration HPLC. The value was assigned by transfer from ERM-DA470 using immunoassay systems qualified based on the linearity and variability observed in dilution tests of pooled urine and the calibrators. Effectiveness of recalibration using the cRM-UA was evaluated by measuring 129 urine specimens.
  
  
  RESULTS
  The cRM-UA had a monomeric albumin peak which accounted for 98.9% of the total area by gel filtration HPLC. The lyophilized preparation of the cRM-UA had suitable homogeneity, and short- and long-term stability. Nine of 14 immunoassays met the criteria were used for value assignment. The assigned concentration was 225.1±9.11 mg/l [mean±U: expanded uncertainty with k=2] when reconstituted with 3.00 ml of purified water on weight basis. Recalibration of 7 qualified immunoassays using the cRM-UA resulted in between-method CV of 6.6%.
  
  
  CONCLUSIONS
  The cRM-UA was successful in achieving standardization of urine albumin results among 7 immunoassays which possess performance attributes representing uniform reactivity to both cRM-UA and clinical urine samples.
authors.affiliation: Department of Laboratory Medicine, Asahikawa Medical University, Asahikawa, Hokkaido, Japan. yoshiito@asahikawa-med.ac.jp
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Itoh
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Ichihara
authors.forename: Kouji
authors.initials: K
authors.lastname: Kishi
authors.forename: Shigemi
authors.initials: S
authors.lastname: Hosogaya
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Yamada
mesh_terms: D000419:Albuminuria / Q000652:urine*; D002138:Calibration; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D012015:Reference Standards; D012709:Serum Albumin / Q000032:analysis*
chemical_list: D012709:Serum Albumin