Journal of Lipid Research, Vol 30, 597-606, Copyright © 1989 by Lipid Research, Inc.
Comparison of two commercial nephelometric methods for apoprotein A-I and apoprotein B with standardized apoprotein A-I and B radioimmunoassays
JL Adolphson and JJ Albers
Department of Medicine, University of Washington, Seattle 98104.
Normotriglyceridemic and hypertriglyceridemic samples were analyzed for
apoproteins A-I and B using the Beckman Array System and the Behring
Nephelometer, and the nephelometric values were compared to values obtained
by highly standardized radioimmunoassays developed at the Northwest Lipid
Research Center. Although the means of the apoA-I values obtained by each
method were similar, comparison of sample values by least-squares
regression analysis revealed large differences (Sy = 20 mg/dl for Beckman,
Sy = 18 mg/dl for Behring) (Sy = standard error of the estimate) regardless
of whether the comparison included hypertriglyceridemic samples. For
normotriglyceridemic samples, there was good agreement between apoB values
obtained by the Behring Nephelometer and those obtained by RIA (r = 0.91, m
= 1.03, Sy = 12 mg/dl). However, significantly higher apoB values were
obtained on hypertriglyceridemic samples by the Behring Nephelometer. ApoB
values for normotriglyceridemic samples obtained by the Beckman System and
RIA showed fairly good correlation (r = 0.86, m = 0.71, Sy = 14 mg/dl).
However, the nephelometric values for normotriglyceridemic samples averaged
29% lower than those obtained by RIA. This difference could largely be
accounted for by the low apoprotein B value assigned to the Beckman
calibrator. Significantly lower apoprotein B values were obtained on
hypertriglyceridemic samples by the Beckman Nephelometer even after
correction for calibration differences. Apoprotein values obtained by
nephelometric methods may be inaccurate, particularly if the samples are
hypertriglyceridemic.