title: Carotenoids, retinol and tocopherols in blood: comparability between serum and plasma (Li-heparin) values.
abstract: OBJECTIVE
  To assess the comparability of concentrations of retinol, alpha- and gamma-tocopherols and individual carotenoids in serum and (Li-hep) plasma over a wide range of concentrations.
  
  
  METHODS
  One hundred sixty-six pairs of samples (serum and lithium-heparin plasma) were analyzed by a quality-controlled HPLC method. Means and 95% confidence intervals, differences, interchangeability and the degree of agreement (Bland-Altman plot) were calculated.
  
  
  RESULTS
  Distribution of all analytes in the two matrices are comparable and interchangeable with minor quantitative adjustments. Within the range of concentrations assessed, the degree of agreement was high, although some differences were observed for minor components with greater analytical imprecision.
  
  
  CONCLUSIONS
  The results indicate an acceptable degree of agreement using either of the two matrices for the analytes assessed except possibly for minor blood components. For retinol and alpha-tocopherol, the comparability and interchangeability of results below the cut-off points for inadequacy need further confirmation.
authors.affiliation: Unidad de Vitaminas, Servicio de Endocrinología y Nutrición, Hospital Universitario Puerta de Hierro, C/ San Martín de Porres, 4 Madrid 28035, Spain. bolmedilla.hpth@salud.madrid.org
authors.forename: B
authors.initials: B
authors.lastname: Olmedilla-Alonso
authors.forename: F
authors.initials: F
authors.lastname: Granado-Lorencio
authors.forename: I
authors.initials: I
authors.lastname: Blanco-Navarro
mesh_terms: D001800:Blood Specimen Collection; D002338:Carotenoids / Q000097:blood*; D006493:Heparin; D006801:Humans; D008094:Lithium; D010949:Plasma / Q000737:chemistry*; D015203:Reproducibility of Results; D024505:Tocopherols / Q000097:blood*; D014801:Vitamin A / Q000097:blood*; D024502:alpha-Tocopherol / Q000097:blood; D024504:gamma-Tocopherol / Q000097:blood
chemical_list: D014801:Vitamin A; D002338:Carotenoids; D024504:gamma-Tocopherol; D006493:Heparin; D008094:Lithium; D024502:alpha-Tocopherol; D024505:Tocopherols