We are in the process of changing our preffered BBK tube from a plain
red top (no additives, yeilds serum) to an EDTA pink top (yeilds
plasma). for use in routine antibody screens and identifications. We
had hoped to benifit from the faster processing times of plasma i.e.
you don't have to wait for it to clot. Over the last few weeks we have
increasingly run into problems with fibrin producing "false positive"
type reactions in MTS cards typically looking like a 1+ reaction, and
also turning up as clumps in tube crossmatches from these tubes. I
don't understand why we are seeing fibrin precipitate in plasma from
these tubes, as I thought that's what the anticoagulant was there to
prevent.Perhaps the anticoagulant is being diluted away when mixed
with MTS solution and/ or saline in red call suspensions. It is very
troublesome because unlike fibrin from serum samples which is clear
cut and recognizable a top line of percipitate on the colllum the
plasma fibrin looks like a genuine positive reaction, and we waste a
lot of time setting up panels and chasing what turns out to be fibrin
or as I like to call it "Anti-MTS".
So; does anyone else have any experience/ input on fibrin in plasma
samples for BBK testing ?

TIA

Rick H