C/T Ratio

[Joanne P. Scannell]

CAP and FDA.

Out of curiousity, who accredits your transfusion service?

[Joanne P. Scannell]

Am I 'hearing' this right? So when manufacturers state that testing has to be performed within x days (and they always say that donor units are ok until outdates), there is NO scientific evidence for these statements?

[Mabel Adams]

That's what I was just wondering too, Joanne. I know they all list donor units until expiration.

[B.Bullock]

If the questions arose from my note, I was referring to a study of expired reagent red cells. The study looked at cells out to three months post expiration. In-date cells are studied by reagent manufacturers extensively.

[Mabel Adams]

To recap what I think we are talking about (at least on one conversation on this thread):

Malcolm thinks that antigens on stored donor units might deteriorate during storage more than antigens on reagent cells and so it would not be safe to use a strongly reacting patient sample to "screen" units for compatibility. We have evidence that manufacturers of typing sera claim that they should be able to detect antigens on stored units up until unit expiration. Some of these reagents do not react any more strongly with positive controls than do Joanne's patient samples. Malcolm has evidence of some antigen deterioration but that was for cells stored in LISS which is not really how the donor cells in question are stored. Becky's Transfusion article is regarding antigen stability in reagent cells not donor cells. We all count on the AHG crossmatch to detect incompatible donor cells when either we have made a typing error (heaven forbid) or when the antigen is low frequency (or we lack the antisera for some other reason). It sounds like there is no evidence either for or against antigen stability on donor red cells over their entire storage period. Sounds like a good SBB student project.

[Malcolm Needs ☆]

Actually Mabel, I have looked into this a bit more and have found a couple of papers that refute some, but not all, of what I have said, with direct relationship to storage of donor red cells and antigen stability. They are;

Snyder EL, Hezzey A, Joyner R, Davisson W, Buchholz DH. Stability of red cell antigens during prolonged storage in citrate-phosphate-dextrose and a new preservative solution. Transfusion 1983; 23 (2): 165-166.

The new preservative mentioned in the title was ADSOL.

Synder EL, Hedberg SL, Napychank PA, Roberts C, Kagen L, Aster RA, Quinlan K, Strucaly A, Buchholz DH. STability of red cell antigens and plasma coagulation factors stored in a non-diethylhexyl phthalate-placicized container. Transfusion 1993; 33(6): 515-519.

I must admit to only having had time to read the abstracts of these papers at present, but the drawback seems to be that, in both cases, they were using reagent-grade antibodies for the experiments, rather than weak antibodies from patients.

[Mabel Adams]

I was just reading the AABB Technical Manual p482 and it says that "because red cells from donors are often fresher than commercial reagent red cells, some antibodies give stronger reactions with donor red cells than with reagent red cells." Further down the page it says, "Antigens on red cells from clotted samples tend to deteriorate faster than antigens on red cells from donor units that are collected in citrate anticoagulants such as acid-citrate-dextrose (ACD) or citrate-phosphate-dextrose (CPD). Red cells in donor units collected in approved anticoagulants generally retain their antigens throughout the the standard shelf life of the blood component." I really should remember to check this reference more often.

[Malcolm Needs ☆]

I would take that with a bit of a pinch of salt Mabel. CR1-related antigens certainly do not.

[Mabel Adams]

There was more on the page than I included. It mentioned that the Kn and Mc antigens weakened with storage and sometimes Duffy as I recall. I was sort of hoping people would read the whole entry if they wanted more information. Sorry if I didn't make clear that there was more on the topic.

[Eoin]

There seems to be two threads on this forum. - SO

 

What I am interested in is targets for C/T ratios. I guess this woulkd be for three or more populations - medical where it should be close to a C/T of 1.0, surgical {where more leeway, especially neuro and spinal surgery would be expected} and trauma. 

 

I am interested in BBs not using electronic issue, but crossing and holding units.

 

I did a literature survey and there is a wide disparity in C/T targets, so am interested in your thoughts folks. 

 

Cheers

 

Wayne (Eoin).

[NYCA]

Eoin,

Have you gotten any input re: C/T ratios ? Our surgical services department is the only one that exceeds our cutoff of <2.0. I don't see anything wrong with that, because frankly I'd rather have blood crossmatched on high-risk procedures and then release the units the next day if not needed. Would you be so kind and share your findings of the survey you did? Thank you!