Estimation of LDL-associated apolipoprotein B from measurements of triglycerides and total apolipoprotein B.
BACKGROUND
VLDL and chylomicrons may interfere with measurements of apolipoprotein B (apo B) on LDL particles. Ultracentrifugation of samples enriched in chylomicrons and VLDL and subsequent measurement of apo B in the infranate fraction [density (d) = 1.006] removes this interference. This apo B fraction is called "LDL-apo B."


METHODS
We retrospectively analyzed 64 895 measurements of triglycerides, total apo B, and LDL-apo B. Samples were ultracentrifuged, and 3 commercially available immunoassays that use different antibodies were used to measure LDL-apo B in the 1.006 infranate fraction.


RESULTS
After adjusting for triglyceride concentration, we found total apo B and LDL-apo B measurements to be strongly correlated. We derived a simple linear equation for calculating LDL-apo B concentration (in milligrams per deciliter) from measurements of total apo B and triglycerides: LDL-apo B = apo B - 10 mg/dL - triglycerides/32. This equation accurately predicts LDL-apo B values within +/- 12% of the measured value in 75% of cases.


CONCLUSIONS
Our equation provides a convenient means of estimating LDL-apo B from commonly available measurements of total apo B and triglycerides without the need for ultracentrifugation. LDL-apo B measurements were also independent of the different apo B antibodies in the 3 assays used in this study. An equation that predicts LDL-apo B particle number may be useful, regardless of the apo B assay used.
Baca
Arthur M
AM
Berkeley Heartlab Inc, Alameda, CA 94501, USA. abaca@bhlinc.com
Warnick
G Russell
GR
D000465:Algorithms; D001055:Apolipoproteins B / Q000097:blood*; D006801:Humans; D007118:Immunoassay; D008077:Lipoproteins, LDL / Q000097:blood*; D012189:Retrospective Studies; D014280:Triglycerides / Q000097:blood*; D014461:Ultracentrifugation
D001055:Apolipoproteins B; D008077:Lipoproteins, LDL; D014280:Triglycerides