Hellllp me with this please

[leema]

A 25 years old female, thalassaemic on regular transfusion, antibody screening is negative and positive DAT, why would it be incompatible with compatible ABO and Rh donor unit??? the donor unit is DAT negative, :frown:

is it possible that the patient developed an antibody thats not in the commerical cells?? if so how would I type the antibody?

[Deny Morlino]

Is it possible you are dealing with a new antibody in the early stages of formation due to a prior transfusion? The antibody may be bound to the RBC's and would need to be eluted for identification.

This is a section from the technical manual:

1. History of recent transfusion. When a patient has recently been transfused, a positive DAT may be the first indication of a developing immune response. The developing antibody sensitizes the transfused red cells that have the corresponding antigen and the DAT becomes positive; the antibody may not be of sufficient quantity to be detected in the serum. Antibody may appear as early as 7 to 10 days after transfusion in primary immunization or as early as 1 to 2 days in a secondary response4,9; these alloantibodies could shorten the survival of red cells already transfused or given in subsequent transfusions

A developing ab may have a titer too low to be detected by an antibody screen, but strong enough to cause reactions during crossmatch.

Not too much help here but may be a place to start . Good luck with it.

[leema]

Thanx Deny for your reply, I did the acid elution today and came negative :frown:

[Malcolm Needs ☆]

It could be an antibody directed against a low incidence antigen (especially in a thalassaemic patient, as they tend to make antibodies of such specificities) that the red cells of the unit just happen to express.

Finding the specificity of such an antibody is very difficult without a vast range of red cells positive for low incidence antigens, and is not very rewarding.

I would go for cross-match compatible blood.

:):)

[Deny Morlino]

Malcolm spoke my next thought. If was thinking cross match compatible might be the next logical choice. Let us know what you decide.

[leema]

Well, I manged to find compatble blood for her as I crossmatched 3 units and two of them were compatible, however my question is, what would possibly be the reason for this incompatiblity, am i goining to face the problem again next time? if by mistake this blood were transfused to her will it cause transfusion reaction?

[JOANBALONE]

Hi Leema,

I would run a panel. Your screening cells may be heterozygous for several antigens such as M, Fyb etc and therefore may not react with a weak antibody. Your crossmatch cell, on the other hand, may be homozygous for the antigen and react with a weak antibody. Or it could be a low.

[LaraT23]

Unfortuantely you have just stepped into the proverbial grey area of blood banking. You may have to resort to that phrase we all loathe.. the dreaded "least incompatible". It would be nice if the patients all read the text books and their specimens behaved accordingly! From what I am hearing it does sound like a low incidence. As for the DAT, is the patinet on any medications that could cause this? The DAT and the incompatibility may not be related, but may represent two different issues.

[Malcolm Needs ☆]

Unfortuantely you have just stepped into the proverbial grey area of blood banking. You may have to resort to that phrase we all loathe.. the dreaded "least incompatible". It would be nice if the patients all read the text books and their specimens behaved accordingly! From what I am hearing it does sound like a low incidence. As for the DAT, is the patinet on any medications that could cause this? The DAT and the incompatibility may not be related, but may represent two different issues.

It is possible that the DAT has been caused by the unit that initially immunised the patient (if this was recent), but the eluate would appear negative unless tested against the same donor.

The possible low incidence antigen on the incompatible unit may be of a different specificity, as people tend to make a "soup" of antibodies directed against low incidence antigens, and so this unit may be compatible with an eluate made from the paqtient's red cells.

Just my musings!

:):)

[adiescast]

I have to agree with Malcolm. At this point the best bet is an antibody to a low frequency antigen. Is the current sample incompatible with any of the previously transfused units?