DCT+ Donor

[Kandahlawi]

Hi, there are 2 case scenario 

1. In my country, we still do AHG crossmatch in all requested blood even though the antibody screening is negative/negative history of antibodies. Just wonder, if you do IS / electronic crossmatch only, there is risk that you might missed out DCT+ donor that only can be detected by AHG crossmatch. 

2. We provide 4 unit of O RhD+ Pack red cells to be keep at Emergency Department to be used in life threatening bleeding. We will do retrospective crossmatch (AHG phase) once they use the blood using the segment from used blood bags and patients pretransfusion sample. Therefore, we routinely check DCT to each unit before issued, to ensure there is no problem with the AHG crossmatch later on.

What is your comment? Thanks

[yan xia]

I think this is a very good question. We have  encountered several  DCT+ donors, the bloods have been returnted to blood center. I just wonder whether it is significant of the  donor DCT+ , anyway they are eligible to donate.

[Malcolm Needs ★]

Personally, I would not worry too much about a donor who has a positive DAT.

We know that a certain percentage of fit, healthy individuals have a positive DAT for no apparent reason, but the fact that they are fit and healthy, and have a high enough haemoglobin and haematocrit to be able to donate blood, and not keel over themselves, means that their red blood cells are almost certainly surviving normally in their own circulation (or, at the very least, the red blood cells are surviving long enough not to compromise the donors health), and they will almost certainly survive long enough in the recipient's circulation to be efficacious, even if they do not survive quite as long as would be expected.  Such red blood cells are most unlikely to be the cause of some form of haemolytic crisis, just because they are DAT positive.

In fact, the NHSBT no longer routinely test their donors for a positive or negative DAT, and we have seen no incidents as a result.

Edited May 12, 2016 by Malcolm Needs
Added the last sentence.

[exlimey]

I agree with Malcolm's comments and would add that I suspect that many positive DATs in donors occur after collection of the blood, i.e., the donor is not actually DAT+ in vivo, but somehow the red cells pick up globulins during exposure to the chemicals and environment of the collection system. 

[Malcolm Needs ★]

31 minutes ago, exlimey said:

I agree with Malcolm's comments and would add that I suspect that many positive DATs in donors occur after collection of the blood, i.e., the donor is not actually DAT+ in vivo, but somehow the red cells pick up globulins during exposure to the chemicals and environment of the collection system. 

I see from where you are coming, but, when we used to test donors for DAT in the UK, it was done on the satellite tubes, where the blood from the arm was allowed to flow straight into EDTA tubes, and only a small percentage gave a positive DAT.

[exlimey]

39 minutes ago, Malcolm Needs said:

I see from where you are coming, but, when we used to test donors for DAT in the UK, it was done on the satellite tubes, where the blood from the arm was allowed to flow straight into EDTA tubes, and only a small percentage gave a positive DAT.

A valid point. It is not uncommon to find a spurious positive DAT in a sample collected in EDTA tube, especially in "older" tubes.

My point is that crossmatches use segments (pigtails) and the presence of the sugary-goodness in the collection systems can also cause positive DATs.

[Malcolm Needs ★]

Oh, I see what you mean, and you are, of course, correct!

[Kandahlawi]

Thanks for the responses. I read in one article, the incidence of DCT positive among donor is only around 1 in 1000 to 14,000 depend on the specificity of the methods used..i think its about time for my country to omit AHG crossmatch in the procedure..the other argument is that the reagent/screening panel cells is of caucasian origin, so we might missed out some low frequency antigen that are prevalence in our population but not in among caucasian..but again, form our experience, such case is extremely rare. Usually if antibody screening is negative, the AHG crossmatch will be mostly compatible, except in very small percentages will give AHG crossmatch incompatible (and almost all of it are due to DCT positive donor)..