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DAT- if micro pos, do you do an eluate?


Karrieb61

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Would you always do an eluate in the following scenario? Mother is group O Pos, antibody screen negative at delivery. Baby is group A Pos (or group B ) DAT positive. Do you have to do an eluate to prove the antibody causing the Positive DAT is maternal anti-A or anti-B and not a rare antibody that wasn`t detected when the mother had her screen done? Or can you just state the DAT is positive probably due to maternal anti-A (or anti-B )

In my hospital we do eluates for all cases like these, and I think we are wasting our time.

 

We do an Immune Anti-A/Anti-B test with cord blood panels where mom is O and baby is A or B. If the Immune Anti-A/Anti-B is positive with the positive DAT, that's all we do - no elution. If the the Immune is negative and the DAT is positive, we would ask the pathologist to evaluate the clinical condition of the baby and let him/her decide whether or not to perform an elution.

 

How often do we do the elution?.....I can't remember the last time we did one.

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If the DAT is positive (we use gel, but if we happen to use tube testing then yes, everything counts) AND the patient has been transfused recently (still debating the definition of 'recently'), we prepare and test an eluate.

 

Keeping in mind that even if the entire unit were transfused, only approximately 10% of the circulating RBCs in the patient will be donor cells ... now remove those donor cells that are being destroyed ... so, ummm, why do we expect a strong positive DAT then?  (We actually had a mistransfusion (nurses not doing the ID of the patient because 'they know who they are working on') where an entire unit of Group A was transfused to a Group O patient ... the DAT was negative.)

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We do an Immune Anti-A/Anti-B test with cord blood panels where mom is O and baby is A or B. If the Immune Anti-A/Anti-B is positive with the positive DAT, that's all we do - no elution. If the the Immune is negative and the DAT is positive, we would ask the pathologist to evaluate the clinical condition of the baby and let him/her decide whether or not to perform an elution.

 

How often do we do the elution?.....I can't remember the last time we did one.

AMcCord may I ask how often do you get Immune anti-A/anti-B negative with Positive DAT?

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We often see cases with neg DAT, but eluation is pos in ABO HDFN.

I have ask the physician  the meaning of this test , they say if we can eluate anti-A /anti-B, then they will give the infant immunoglubulin in treatment, if not then not give.

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AMcCord may I ask how often do you get Immune anti-A/anti-B negative with Positive DAT?

 

I don't think we've seen a negative Immune anti-A/anti-B with a positive DAT and an O mom. That's one of the things I look at specifically when I do supervisory review. Of course, the majority of type A or B babies with a type O mom do not have a positive DAT. 

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  • 1 month later...

We do an Immune Anti-A/Anti-B test with cord blood panels where mom is O and baby is A or B. If the Immune Anti-A/Anti-B is positive with the positive DAT, that's all we do - no elution. If the the Immune is negative and the DAT is positive, we would ask the pathologist to evaluate the clinical condition of the baby and let him/her decide whether or not to perform an elution.

 

How often do we do the elution?.....I can't remember the last time we did one.

I'd love to get rid of elutions...some of our older doctors have now retired and we haven't had an elution ordered for at least a year.  What is the Immune AntiA/AntiB test you are speaking of?  MAnufacturer, etc??  Most of time with a positive DAT on cord bloods doctor's go ahead and start the bili lights when we call the result.  Occasionally, one dr would order an elution and it would usually be ABO incompatibility.  

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I'd love to get rid of elutions...some of our older doctors have now retired and we haven't had an elution ordered for at least a year.  What is the Immune AntiA/AntiB test you are speaking of?  MAnufacturer, etc??  Most of time with a positive DAT on cord bloods doctor's go ahead and start the bili lights when we call the result.  Occasionally, one dr would order an elution and it would usually be ABO incompatibility.  

 Immune Anti-A/-B is an AHG test of baby's serum/plasma with A and B reagent cells (with enhancement). A positive test indicates the presence of Anti-A or -B from mom. No need for an elution.

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Hi Karrieb61,

Are you referencing performing eluates for pos-transfusion investigation or for mother/baby ABO incompatibility?

My view is that the DAT is a crappy test . . . er, ahem . . . it is not a sensitive test.  One can easily get a negative DAT and end up getting a specificity out of the eluate, since the eluate concentrates the antibody. 

At our facility we currently look at all DAT's microscopically, which is a bit of carryover from previous management.  We do eluates on micro + DAT's if the patient has been transfused in the last 2 weeks.  If I remember right, we have gotten specificities out of eluates performed on samples with micro + DAT's (at least if I remember right.  Help me out here, Mabel.) For babies, we still report the DAT as pos (even if just micro+) and that is where the workup stops.  We don't do further investigation to prove it is maternal anti-A or anti-B causing the positive DAT.  However I suppose we would investigate further if the physician requests us to do so.

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Well, Whitney, I wouldn't agree that the DAT is 'not a sensitive test'.  But it isn't always very specific (which isn't the same thing).  And if you're microscoping all your negs, you are erring on the side of much too sensitive for purpose.  The DAT is a useful tool, but no more than that, and it should never ever be used out of context otherwise the results are meaningless.  See my previous rants on this issue in this same thread!

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Hello again, First of all, no I wasn't referring to babies since we don't transfuse babies here for starts and our current policy says that if the DAT is positive, we "consult the physician" which we haven't had to do, maybe never.

I was talking about adult positive DATs. I did a ton of research on this, partly to improve my old knowledge since I was out of technical blood banking for years prior to coming to my current job, and partly to get a consensus before making any changes here.

For now, we are doing DATS on the Echo, complement, when required, by tube of course. We aren't doing eluates anymore, and I have written the procedure to send out an eluate if the patient was transfused up to 3 months ago and the DAT was positive. We've done that twice maybe and they found nothing new that we didn't pick up in the ABID on the Echo.

I am now routinely talking with the Reference Lab we work with - if our Echo DAT is positive at 1+ or 2+, its very likely that a tube DAT will be negative  completely, including microscopically. Therefore our Ref Lab wouldn't bother with an eluate if they start with repeating the DAT by tube and it's negative. So things will remain confusing to a point since we will probably always see at least slightly pos DATs with the Echo that will be negative elsewhere.

Finally, micro DATs- I was going to dump them but a local Transfusion MD for whom I have great respect says that micro DATs may be valuable. So for now, I'm not changing any of our micro reading SOPs. More on those later on. I personally think that micro readings are value less because we all interpret these differently and way too many techs will call sticky cells 'weak pos" to avoid thinking that they are missing something important. We only have one dedicated blood banker and the other techs aren't in there often enough to gain a ton of confidence when these sticky situations develop.

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In my experience the DAT is highly subjective to variables such as the method/reagent, the laboratory technique of the technologist (e.g. 'shaking' of the tube), reaction grading, and the circumstances surrounding the test performance (e.g. what else is going on to delay the testing/disorient the technologist).

This is basically why we permit microscopic readings. I'd rather that someone saw the 1+ reaction that they shook away as a microscopic reaction due to poor/hasty technique. It's also not a help that the manufacturer insert clearly indicates: "examine negative reactions with an optical aid."

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  • 2 weeks later...

Back to the daily DAT question: could a physician possibly be trying to monitor some type of drug interaction for his/her patient? Trying to think outside of my little box here.

I don't know about daily.  I did work at an institution that performed drug studies for pharmaceutical companies and they always ordered DATs on those patients. It might be required. I have seen in the PDR - Physicians Desk Reference - for drugs - positive DAT listed as side effects.

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  • 6 months later...

Sometimes the DAT can be negative due to destruction of the cells. Just because it is negative does not mean that there is not An underlying antibody present. Sooo, if your DAT is positive, regardless of the strength! you should perform the eluate.

Sometimes the DAT can be negative due to destruction of the cells. Just because it is negative does not mean that there is not An underlying antibody present. Sooo, if your DAT is positive, regardless of the strength! you should perform the eluate.

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Sometimes the DAT can be negative due to destruction of the cells. Just because it is negative does not mean that there is not An underlying antibody present. Sooo, if your DAT is positive, regardless of the strength! you should perform the eluate.

Sometimes the DAT can be negative due to destruction of the cells. Just because it is negative does not mean that there is not An underlying antibody present. Sooo, if your DAT is positive, regardless of the strength! you should perform the eluate.

 

DCeDCe - does your name mean that you repeat your posts too? Hee hee ;)

 

You make a very good point though

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