International Federation of Clinical Chemistry standardization project for measurements of apolipoproteins A-I and B.

To minimize differences in apolipoprotein measurements among laboratories and methods, a standardization program involving common suitable reference material is needed. The Committee on Apolipoproteins of the International Federation of Clinical Chemistry initiated a collaborative study for the standardization of test systems for measuring apolipoproteins (apo) A-I and B, with 25 company laboratories and three research laboratories involved in apolipoprotein analysis to: (a) evaluate calibration differences among the test systems; (b) evaluate whether comparability of the data can be achieved with the use of frozen serum pools to recalibrate the different systems; and (c) evaluate and select suitable candidate reference material. We used 26 test systems for apo A-I and 28 for apo B. Relatively modest differences were found in calibration for apo A-I, but very wide differences were observed for apo B methods. After uniform calibration, the overall among-laboratory CV for apo B decreased from 19% to 6%. Three lyophilized serum preparations for apo A-I and three liquid-stabilized serum preparations for apo B were selected for further evaluation as candidate international reference materials.