Rate immunonephelometry and radial immunodiffusion compared for apolipoproteins AI and B assay

We measured apolipoproteins (apo) AI and B in fresh plasma samples and serum control pools by using two rate immunonephelometric assay (INA) methods (Beckman "Array" and Behring) and radial immunodiffusion (RID). Both INA methods on average gave apoAI values similar to those by RID in fresh plasma samples. The coefficients of correlation for the two INA-RID method pairs were as follows: Beckman INA vs RID, n = 94, r = 0.73; and Behring INA vs RID, n = 112, r = 0.66. The bias between the INA and RID methods was reflected reasonably well by either lyophilized or frozen control pools. For apoB, the Beckman INA measurements in fresh plasma averaged 40% lower than RID values, due almost entirely to the values assigned to calibration sera, but results by the two methods were highly correlated (n = 94, r = 0.93). The Behring INA values for fresh plasma averaged only 13% lower than RID values, but the two methods were less well correlated (n = 112, r = 0.74). Frozen control pools were most suitable for apoB analysis.