From Tiffany Jones, Orlando Health: I was wondering if you could clarify for me why we can't use a blue citrate tube for a platelet count after it has been spun once. Are there any studies to back up this reason? My facility seems to get a fair amount of patients displaying EDTA-induced platelet clumping and we resort to asking for a recollect on the patient because if a blue top had been drawn, in all likelihood it was spun in the coagulation department. It also gets a little trickier when the patient is an outpatient draw. Thank you for your time!
Hello, Tiffany, thanks for a provocative question. The short answer is no , having done a literature search, I find there are no published studies that indicate platelet counts from centrifuged and subsequently resuspended citrate whole blood specimens are either valid or unreliable. We rely on expert opinion, which assumes that centrifuged platelets are likely to become activated and clumped. The clumped platelets are unlikely to resuspend evenly. The question is not addressed in the relevant and most recently published CLSI documents, H3 and H21, Procedures for the Collection of Blood Specimens by Venipuncture, and Collection, Transport, and Processing of Blood Specimens for Testing Plasma-Based Coagulation Assays and Molecular Hemostasis Assays, respectively.
I've forwarded your question to two specimen management experts and hope to get additional responses from them. Meanwhile, it may be interesting to run a simple platelet count study in your own laboratory to find out what happens to the platelet count from a resuspended tube. Check back soon for some additional responses.