Minor crossmatch with microcolumn agglutination method

[oxtail652]

In China, we do not carry out the policy of T&S at blood transfusion department.we perform both major and minor crossmatch as a pre-transfusion tests,and we do not perform the antibody screening test for donor units. But, we have problems when we change Tube to microcolumn agglutination method.

There is the highly frequent weak positive result of minor cross match with cassettes. We found the same situation from literatures issued by domestic magazine. The article reports that the positive rate of minor crossmatch is about 10~20% when application of microcolumn , the reason of high positive rate mainly due to Sensitized patient red blood cells, the result of DAT is weak positive. However, the positive results of Tube are very rare.

The questions of minor crossmatch always trouble us, how do we handle this issue? Can we issue the blood unit with weak positive of minor crossmatch ( DAT positive)?

Thanks in advance

[Malcolm Needs ☆]

Just as a matter of interest, why do you perform the minor cross-match?

[Steven Jeff]

Am I right in assuming that you don't do antibody screens pre-transfusion?

Steve

[David Saikin]

If you are doing the minor xm in IgG gel you can expect every pt with a +DAT to be reactive . . . We have not done minor xm in the USA in 40 yrs. Your Medical Director or National Health Agency will have to provide insight on how to deal with transfusing your pts in whom the minor xm appears incompatible.

[fenwayman]

why would donor units get released to product management with incomplete testing(antibody screen) for shipment to your local hospitals and I am not sure why you do the minor crossmatch. It seems to me if the unit is DAT+, all your minor xmatches would be incompatible as David suggests. Seems to me that I would want to ensure your facility that does the donor testing would include an antibody screen on all units prior to release and investigate any units that are DAT+.

[Malcolm Needs ☆]

why would donor units get released to product management with incomplete testing(antibody screen) for shipment to your local hospitals and I am not sure why you do the minor crossmatch. It seems to me if the unit is DAT+, all your minor xmatches would be incompatible as David suggests. Seems to me that I would want to ensure your facility that does the donor testing would include an antibody screen on all units prior to release and investigate any units that are DAT+.

I think the problem is that it is the recipient's red cells that are DAT +ve, and these are being tested aginst (hopefully) inert donor plasma, but because they are already sensitised by the auto-antibody, they would give reactions in the minor cross-match.

[oxtail652]

In many Chinese hospitals, blood units are fully crossmatched due to following reasons:one is that hospital blood banks do not have the manpower and resources to perform complete antibody investigation, another is that the blood center do not perform the antibody screening for donor unit, and the hospital do not test it either since who can not chage the testing fee from donor.In this situation, we have to perform both major and minor XM. There is no problem to do so with conventional tube ITA, but the problems present when new technology introduced.The microcolumn technology is more sensitive than tube one,the recipient'DAT positive will result in minor XM's positive. however, the DAT is not the routine tesing for recipient.

[JOANBALONE]

In China, do you routinely transfuse packed cells or whole blood?

[oxtail652]

we routinely transfuse packed cells

[John Eggington]

What is the source for the plasma you use in the minor crossmatch? If you're getting it from the blood pack (or the tubing attached to the pack) it could be causing 'false positive' reactions in a gel test that you wouldn't get in a tube IAT (because of the wash phase of the tube IAT). Just a thought.

[JOANBALONE]

Just an FYI, in the US, it is not required to do minor crossmatch for packed red blood cells even if the donor has a known antibody, although many hospitals do not accept these units or prefer to wash before giving to patient (some one correct me if I am wrong). To do minor crossmatch you may have several options: 1. For patient's with positive DAT switch to a less sensitive technique such as tube, however, this will not solve all your problems as many minor crossmatches may still be incompatible. 2. Perform an antibody screen on large volume plasma products for patient's with known positive DAT. 3. Perform minor crossmatch and control (patient cells/patient plasma). If minor crossmatch is stronger than control, do not transfuse. (I am not very comfortable with number #3.) Have you asked other colleagues in China what they do?

jb

Edited April 2, 2011 by JOANBALONE
added more

[Mabel Adams]

Where do you get the donor plasma sample to test in the minor crossmatch? From a tubing segment or do you get pilot tubes of donor blood with the unit? If you have enough donor plasma sample that you could spin it down before testing in gel, that might reduce false positives. Nothing will help if the recipient has a positive DAT, of course. If you are giving packed cells rather than whole blood, maybe you could devise a cut-off level. For instance, if the minor crossmatch is weaker than, say, 2+ you would assume that any antibody in the residual donor plasma on the packed cells would be sufficiently diluted as to cause little problem in the recipient.

If the packed cells have additive solution and were leukoreduced after collection, a large part of the "plasma" in the unit's tubing segments is actually additive. In units not leukoreduced, this is probably pure citrated patient plasma. Has anyone validated the use of citrated plasma in gel testing? What effects do the adsol additives have on gel testing? Maybe you could test these things separately so you could determine which are more likely to cause your problem. I hope that 10-20% of your patients don't have a positive DAT, however I have not tested random people in gel for DAT so have no idea how common it would be since it is a more sensitive method. Tube testing was used in the reports I have seen of the frequency of positive DATs in the population.