title: Oxidative modifications impair albumin quantification.
abstract: BACKGROUND
  Hypoalbuminemia is a measure of malnutrition, inflammation and a predictor of mortality in uremia. It is controversial whether albumin levels per se are associated with the clinical outcomes in uremic patients. The co-occurrence of hypoalbuminemia and oxidative stress in hemodialysis (HD) patients led us to hypothesize that oxidative modifications of albumin decrease its detection and influence albumin quantification.
  
  
  METHODS
  Albumin levels are determined in clinical laboratories mainly by the bromocresol green (BCG) spectrophotometric assay. The detection of serum albumin was investigated in HD patients and in healthy controls using an "albumin-detection index", defined as the ratio between BCG read-out (albumin-specific) to total albumin. The detection efficacy of albumin was also investigated in vitro, after glycoxidation, HOCl-mediated-oxidation, and metal-catalyzed-oxidation. Oncotic pressure was measured to assess albumin function.
  
  
  RESULTS
  The albumin-detection index of patients was significantly lower compared with controls, correlating negatively with oxidative stress markers (serum advanced oxidation protein products-AOPP and glycoxidized serum albumin) and positively with serum albumin levels. The albumin-detection index was also decreased after in vitro oxidation.
  
  
  CONCLUSIONS
  The study shows, both in vivo and in vitro, decreased detection of oxidized albumin by a commonly-used clinical assay, thus providing the molecular link between oxidative stress and hypoalbuminemia. Oxidative stress as reflected by hypoalbuminemia, rather than actual albumin levels, may be related to cardiovascular morbidity outcomes in HD patient.
authors.affiliation: Eliachar Research Laboratory, Western Galilee Hospital, Nahariya, Israel. Regina.Michelis@naharia.health.gov.il
authors.forename: Regina
authors.initials: R
authors.lastname: Michelis
authors.forename: Batya
authors.initials: B
authors.lastname: Kristal
authors.forename: Tamara
authors.initials: T
authors.lastname: Snitkovsky
authors.forename: Shifra
authors.initials: S
authors.lastname: Sela
mesh_terms: D000328:Adult; D000419:Albuminuria / Q000097:blood*; D002318:Cardiovascular Diseases / Q000097:blood / Q000209:etiology* / Q000401:mortality; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011487:Protein Conformation; D006435:Renal Dialysis / Q000009:adverse effects*; D012709:Serum Albumin / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism*
chemical_list: D012709:Serum Albumin