Standardization of commercial assays for serum Apo A-I and Apo B: a consensus procedure for the calibration of reference materials.

Commercial apolipoprotein A-I and B assays show a broad variation of results. This is particularly evident for the different Apo B test kits available commercially. The cause of these differences is mainly due to the inadequate international standardization of apolipoprotein assays. A common effort is at present made by commercial organizations within the International Federation of Clinical Chemistry together with the IFCC Committee on Apolipoproteins to achieve a consensus on a practical standardization procedure for apolipoprotein measurements. The aim is to calibrate all commercially available Apo A-I and Apo B test kits using frozen serum pools (at three levels) previously standardized against primary reference materials. Secondary serum reference materials (at three different concentrations) (SSRM) will be selected among those offered by industrial organizations to serve as "International Master Calibrators". These will replace the Interim Serum Reference Materials (frozen serum pools) which cannot be delivered indefinitely. The secondary serum reference materials will be used by all commercial organizations to control the validity of their own calibrations.