dat's with phenotyping

[Kwenz]

When you are phenotyping DONOR UNITS, do you do a DAT on all positive results to prove that the result is due to the presence of antigen on the cell and not because the unit has a positive DAT? I understand the need for this on a patient but question the need to do it on a donor unit.

[johna]

When you are phenotyping DONOR UNITS, do you do a DAT on all positive results to prove that the result is due to the presence of antigen on the cell and not because the unit has a positive DAT? I understand the need for this on a patient but question the need to do it on a donor unit.

I don't see what the point would be. If you are looking for antigen-negative units and the donor result was antigen-positive you would exclude the donor anyway.

[johna]

I don't see what the point would be. If you are looking for antigen-negative units and the donor result was antigen-positive you would exclude the donor anyway.

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Correction on my previous post. After thinking about this for a while I've come to the conclusion that a DAT would be appropriate since you would want to label these units as antigen-positive, (even though you wouldn't be using them for the patient being crossmatched) and would want to ensure that the results were correct. I've been away from the hospital blood bank side of things too long!

[Yanxia]

I think it is no need to do DAT on all antigen-postitive units. To do a donor's antibodies screening, it will include auto-control that can reflect the DAT status. And if a unit is DAT positive, especially IgG1 or IgG3 it is danger to transfuse this kind of blood.

This is just my personal view.

Yanxia

[galvania]

Well, wouldn't it depend on the antigens you were screening for? I would have thought that if you were looking for antigens using a coombs technique, then it would be good practise to include a DAT as a negative control. (For all antigens tested by coombs on the DiaMed gel cards, this requirement is actually written in to the box insert); but if you are using another technique then a different, relevant, control would be needed to validate the results (eg if tested by enzymes, then a control using the patient's cells treated with enzymes against, for example 2% albumin)

[OPUS104]

This is a big debate with our QA dept. right now. Often when looking for multiple antigen negative units we (of course) quit testing a unit if the first antigen is pos. Most antisera inserts state that a DAT must be performed to verify the positive result.........................crazy for us to do for one Fya result,..........but we record pos. results in donor history. Thus the fight with QA. This is another case of company CYA in the inserts that causes us untold hassle with QA.

[galvania]

This is a big debate with our QA dept. right now. Often when looking for multiple antigen negative units we (of course) quit testing a unit if the first antigen is pos. Most antisera inserts state that a DAT must be performed to verify the positive result.........................crazy for us to do for one Fya result,..........but we record pos. results in donor history. Thus the fight with QA. This is another case of company CYA in the inserts that causes us untold hassle with QA.

But surely the company would be negligent if it did NOT tell you to do this, and you falsely reported a unit as Fya+ when it was in reality Fya- with a positive DAT.....

[bbbirder]

I keep going back to the earlier statement, "If you are looking for antigen-negative units and the donor result was antigen-positive you would exclude the donor anyway." and I think this is correct. As a transfusion service (not a donor center) I am looking to protect my patient from an antigen positive unit.

Granted, the unit could be 'mislabeled' as positive for an antigen if it had a positive DAT, but for a transfusion service, I don't think I care. (Should I?)

Linda Frederick

[OPUS104]

Hey bb.....

In that situation I don't see how it could be bad. No long time record and no chance of patient harm........

[Mabel Adams]

I agree this is not a problem for tranfusion services but is for donor centers. Do US donor centers always do DAT or Auto control as part of donor testing?

[OPUS104]

If we get multiple positives when testing coombs....yes. If we only test one antigen and stop if it is positive,,,,,,,no. We are not real concerned about a single "false" positive. Having said that, we are currently reviewing this policy with our QA dept. Any data from any other donor centers would be appreciated.

[Mabel Adams]

I'm just glad that most of the antisera I keep are monoclonal and don't require AHG testing. Sidesteps the problem for all but anti-Fya. (We only keep common antisera.)