International survey of apolipoproteins A1 and B measurements (1983-1984).

We report here results of a worldwide survey of apolipoprotein (apo) A1 and B measurements. A lyophilized pool of human serum was developed for the survey to test its suitability as a candidate Reference Material. Seventy-five laboratories from 18 countries responded to invitations to participate. Using several methods, they evaluated the mass concentration of apo A1 and B in the proposed Reference Material. The bias between laboratories and between analytical methods was then characterized. Fifty-five laboratories reported results before the deadline on measurement of at least one apolipoprotein by one method. Variation in apo A1 and B among collaborators constituted the largest source of error in the study (68% of the total variation for apo A1, 73% for apo B). Variation among method means was not significant for apo A1, but for apo B it constituted 20% of the total variation. Differences due to vials or in replicate measurements within vials were found to constitute 6% or less of the total variability. Within-laboratory, among-vial, and among-replicate CV values were less than 5% for the study. These results suggest that future standardization efforts can be successful.