Clinical Chemistry
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Clinical Chemistry 40: 537-540, 1994;
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Clinical Chemistry, Vol 40, 537-540, Copyright © 1994 by American Association for Clinical Chemistry

Chemiluminescence receptor assay for measuring vitamin B12 in serum evaluated

S Wentworth, JA McBride and WH Walker
Department of Laboratory Medicine, Henderson General Hospital, Hamilton, Ontario, Canada.

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.




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Copyright © 1994 by the American Association for Clinical Chemistry.