Effects of lyophilization of serum on the measurement of apolipoproteins A-I and B.
A common accuracy-based standardization program is indispensable for establishing reference intervals for the clinical use of apolipoproteins. The development and distribution of reference materials and quality-control materials that do not exhibit matrix effects between methods is essential to the standardization process. We examined the suitability of lyophilized material as a common reference material for the measurement of apolipoproteins A-I and B. We determined values for apolipoproteins A-I and B in frozen and lyophilized serum pools, using different immunochemical approaches. We found little or no differences in apolipoprotein A-I values between frozen and lyophilized pools as determined by the different methods. In contrast, values for apolipoprotein B in lyophilized samples were consistently lower than those obtained for frozen samples. After adjusting for the effect of dilution due to reconstitution, the difference in the apolipoprotein B values for lyophilized as compared with frozen samples ranged from -26% to 4%, depending upon the assay method. Evidently, serum pools in lyophilized from are not a suitable matrix for reference materials for apolipoprotein B measurements but can be used for apolipoprotein A-I measurements.
Marcovina
S M
SM
Northwest Lipid Research Center, Harborview Medical Center, Seattle, WA 98104-2499.
Adolphson
J L
JL
Parlavecchia
M
M
Albers
J J
JJ
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A / Q000097:blood* / Q000592:standards; D001055:Apolipoproteins B / Q000097:blood* / Q000592:standards; D001793:Blood Preservation / Q000379:methods; D002784:Cholesterol / Q000097:blood; D005612:Freeze Drying; D005615:Freezing; D006801:Humans; D012015:Reference Standards; D014280:Triglycerides / Q000097:blood
D016632:Apolipoprotein A-I; D001054:Apolipoproteins A; D001055:Apolipoproteins B; D014280:Triglycerides; D002784:Cholesterol