Comparison of apolipoprotein A-I values assayed in lyophilized and frozen pooled human sera by a non-immunochemical electrophoretic method and by immunoassay.
Various immunochemical assays are used for measuring the apolipoprotein A-I in human serum, but results obtained by these assays often cannot be compared owing to methodological problems, the lack of reference methods and inadequate standardization. The electrophoretic apolipoprotein A-I assay avoids the problems associated with antibody-antigen interaction. The method involves spectrophotometric measurement of the Coomassie blue eluted from the apolipoprotein A-I bands of human serum after electrophoresis in a gradient gel. The assay was linear from 0.5 to 4.0 micrograms of apolipoprotein A-I. Within-assay variability was 3.2% and between-assay variability was 5.9%. Overall analytical recovery was 98%. The electrophoretic assay is suitable for the quantitation of apolipoprotein A-I in fresh, frozen or lyophilized serum pools. Analysis of 6 frozen serum pools showed a good correlation between this assay and an immunoturbidimetric assay (r = 0.96), and between this assay and consensus values (r = 0.99). Consensus values were derived from the results of different immunochemical assays performed in 6 laboratories in 3 different countries within 3 years. The mean apolipoprotein A-I concentrations in 3 lyophilized serum pools were 1.04 +/- 0.02, 0.86 +/- 0.02, and 0.45 +/- 0.03 g/l (mean +/- SD) by electrophoretic assay. The consensus values for these pools were 1.04, 0.86, and 0.43 g/l, respectively, as derived from the data of different immunochemical assay measurements performed in 84 laboratories in 34 various countries. The electrophoretic assay has been proposed as an alternative to the immunochemical assays for assigning the target values to reference and control materials, using pure and well-characterized apolipoprotein A-I as a primary standard.
Sigalov
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AB
Biomedical Department, AMW Co Ltd., Moscow, Russia.
D016632:Apolipoprotein A-I / Q000032:analysis*; D001774:Blood Chemical Analysis; D001793:Blood Preservation; D015925:Cryopreservation; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods*; D005612:Freeze Drying; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D015203:Reproducibility of Results
D016632:Apolipoprotein A-I