Centrifuge time and transfused vs. autologous RBCs

[TypeO4life]

Has anyone had any issue with immunohematology automation (analyzers) picking up transfused red cells only for testing vs. transfused + autologous cells?

My lab recently had two specimens, where it appears that the analyzer forward typed only transfused cells for recently transfused patients. This is via gel method. Tube method demonstrated a 4+ reaction when repeated.

I repeated on a different lot of forward typing gel cards, and results were replicated.

I read through previous threads about recommended specimen centrifuge times, and I'm starting to think my centrifuge may be to blame... please share your thoughts!

[galvania]

This is well known and there are indeed other threads concerning this.  Transfused cells may have different densities to the patient's own cells and therefore when you spin the tubes in the centrifuge you may find that the transfused cells and the patient's cells separate.  Then, depending on where you sample from in the tube, you will either get only transfused cells, only patients cells or a mixture, giving a mixed field.  Typically instruments will select cells from the bottom of the tube, whereas pipetting by hand, one normally samples from the top, giving a discrepancy between the two methods.

[TypeO4life]

Thank you for the response! I realize there are different densities, but I couldn't find information as to which was more dense, the transfused versus the patient's own cells? Which type of cells would remain at the top of the red cells when a tube is spun?

[Yanxia]

The transfused cells are denser, so most of them at the bottom, and patients' own cells at the top.

Edited June 4, 2019 by yan xia
typo