From Tanja Skierka:
I have been searching for a reference that supports the use of ultracentrifugation in lipemic samples for prothrombin time (PT), partial thromboplastin time (PTT), and fibrinogen (FG) tests. We are using a Siemens BCS with optical detection and have very good results with their 570 nm alternative for lipemic samples. However, we have occasional patients with hyperlipidemia that is not solved by redraw or 570 nm. We have been told ultracentrifugation is an option, but I have been unable to find a reference.
Hello, Tanja Skerka, and thank you for your question. My primary reference for specimen-related questions is Adcock, D DM, et al. Collection, Transport, and Processing of Blood Specimens for Testing Plasma-based Coagulation Assays and Molecular Hemostasis Assays: Approved Guideline–Fifth Edition. CLSI Document H21-A5, Clinical and Laboratory Standards Institute, 940 West Valley Road, Suite 400, Wayne, PA 19087-1898. The document states, “Ultracentrifugation has been suggested in some circumstances; however, there are no published studies. In a small, unpublished study of lipemic samples, PT and APTT assays were decreased and fibrinogen levels were increased by about 10 to 15%. Until published studies are performed or the laboratory has validated the procedure, mechanical and/or electromechanical methods should be utilized when possible for these samples that are icteric, lipemic, or contain substances that interfere with light transmission.”
I know that most optical coagulometers adequately compensate for lipemia by employing alternate wavelengths, however it appears from the CLSI standard, we cannot use ultracentrifugation with assurance.
Relative to this, I have heard anecdotes that the larger multimers of von Willebrand factor are lost from the supernate during ultracentrifugation, however I’ve been unable to confirm this by reviewing references.