title: Chemiluminescence receptor assay for measuring vitamin B12 in serum evaluated.
abstract: We evaluated a chemiluminescence receptor assay for vitamin B12 in serum (Magic Lite; Ciba Corning Diagnostics), in which an acridinium ester label is used with magnetic particle separation. Within- and between-batch precisions were generally acceptable, except at low analyte concentrations. The reference range determined from 104 elective preoperative patients was 120-610 pmol/L, compared with 150-590 pmol/L for our in-house radioligand-binding assay. Magic Lite discriminated between normal and abnormal results as effectively as the in-house method when local reference ranges were applied. Magic Lite demonstrated a negative bias at low analyte concentrations and was unable to detect any vitamin B12 in two B12-deficient patients. Assay accuracy--judged from analytical recovery and comparisons with the in-house method and two other radioassay kits (Quantaphase, Bio-Rad Labs., and Immophase, Ciba Corning Diagnostics)--was poor at low B12 concentrations when the manufacturer's recommended two-point calibration was used. This problem was partially corrected by using a full set of calibrators.
authors.affiliation: Department of Laboratory Medicine, Henderson General Hospital, Hamilton, Ontario, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Wentworth
authors.forename: J A
authors.initials: JA
authors.lastname: McBride
authors.forename: W H
authors.initials: WH
authors.lastname: Walker
mesh_terms: D006801:Humans; D007700:Kinetics; D008163:Luminescent Measurements; D008280:Magnetics; D008863:Microspheres; D011786:Quality Control; D011869:Radioligand Assay / Q000379:methods* / Q000706:statistics & numerical data; D011933:Reagent Kits, Diagnostic / Q000706:statistics & numerical data; D012016:Reference Values; D012680:Sensitivity and Specificity; D014805:Vitamin B 12 / Q000097:blood*
chemical_list: D011933:Reagent Kits, Diagnostic; D014805:Vitamin B 12