Lipid tests on lipemic serum

Medical Laboratory Observer, April, 2007 by Daniel M. Baer

Q What is the preferred method for running a lipid panel on very lipemic samples? Do you airfuge the sample and run the tests on the cleared specimen, or do you run the tests on the sample, "as is," and then add a qualifying statement about the lipemia?

A This is a good and important question. Assuming that your lipid panel reports total cholesterol, triglycerides, low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C), your best bet is to send very lipemic specimens to an National Heart, Lung and Blood Institute-Centers for Disease Control and Prevention (NHLBI-CDC) standardized laboratory, (1) which uses the classical preparative ultracentrifuge procedure. Airfuging (ultracentrifugation) will remove the chylomicra and very low-density lipoprotein (VLDL), which contains mainly triglycerides. Therefore, the analysis of the clear infranatant solution after ultracentrifugation will not give accurate triglyceride results.

If the specimen is not very lipemic (i.e., triglycerides less than 1,000 mg/dL), you can dilute the original specimen with albuminated saline to obtain an estimate of the triglycerides. Then, the use of the ultracentrifugation procedure will be helpful for the total cholesterol and HDL-C assay. There is one commercial laboratory (Atherotech Inc., Birmingham, AL) that uses the micro-sample preparative ultracentrifuge method to give you direct measurements of all lipoprotein components, including lipemic specimens.

If your lipid panel is restricted to cholesterol, triglycerides, and HDL-C testing, using an airfuge at 100,000 X g for five minutes is an alternative quick method to remove those triglyceride-rich lipoproteins. This will allow you to report total cholesterol and HDL-C.

--Herbert K. Naito, PhD, MBA

NorthStar Consulting Service

Beachwood, OH

References

1. Cholesterol Reference Method Laboratory Network. Available at: http://0-wwwcdcgov.mill1.sjlibrary.org/labstandards/pdf/crmln/Web_TCCert_US_Report.pdf. Accessed January 29, 2007.

"The key to a good laboratory is the professionalism of its staff.
Up-to-date facilities and equipment help, but it is a dedicated,
knowledgeable staff that allows the lab to provide great patient care."
--Daniel M. Baer, MD, MLO editorial advisory board

Daniel M. Baer, MD, is professor emeritus of laboratory medicine at Oregon Health and Science University in Portland, OR, and a member of MLO's editorial advisory board.

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