International Federation of Clinical Chemistry standardization project for measurements of apolipoproteins A-I and B. IV. Comparability of apolipoprotein B values by use of International Reference Material.
We performed temporal and thermal stability studies on SP3-07, a liquid-stabilized reference material for apolipoprotein (apo) B, selected during the previous phase of the International Federation of Clinical Chemistry project on standardization of apolipoprotein measurements. Results indicate that SP3-07 stored at -70 degrees C has the long-term stability required for a reference material. We assigned an accuracy-based apo B value of 1.22 g/L to SP3-07, using a nephelometric method that was calibrated with freshly isolated low-density lipoprotein for which the apo B mass value was determined by a standardized sodium dodecyl sulfate-Lowry procedure. Using a common protocol, the study participants transferred the assigned mass value from SP3-07 to the individual calibrators of the analytical systems and measured the apo B concentration of 20 fresh-frozen samples obtained from individual donors and covering a clinically relevant range of apo B values. The among-laboratory CV on these samples, analyzed by 25 analytical systems, ranged from 3.1% to 6.7%. These results demonstrate the lack of matrix effects of SP3-07 and its ability to provide accurate and comparable apo B values in a variety of immunochemical methods. On the basis of the outcome of these studies, the World Health Organization has endorsed SP3-07 as the International Reference Material for Apolipoprotein B.
Marcovina
S M
SM
Department of Medicine, Northwest Lipid Research Laboratories, University of Washington, Seattle 98103.
Albers
J J
JJ
Kennedy
H
H
Mei
J V
JV
Henderson
L O
LO
Hannon
W H
WH
D016632:Apolipoprotein A-I / Q000032:analysis*; D001055:Apolipoproteins B / Q000032:analysis*; D002138:Calibration; D002624:Chemistry, Clinical / Q000592:standards* / Q000706:statistics & numerical data; D004355:Drug Stability; D006358:Hot Temperature; D006801:Humans; D012015:Reference Standards; D012680:Sensitivity and Specificity; D013997:Time Factors
D016632:Apolipoprotein A-I; D001055:Apolipoproteins B