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Hi All

My manger has decided to send all positive DAT( even if it's weak positive ) to reference lab for elution if patient has been transfused in last 28 days. Is it really necessary to perform elution when there's no sign of haemolysis ? Is there any guidelines to follow for investigation of positive DAT. 

 

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Hi gagpinks,

We perform elutions on positive IgG DAT only if the patient has been transfused or pregnant in the past 3 months.  I do believe that this is up to each facility's individual policy regarding protocol order vs. physician order.  (many positive DAT's are due to infection, medication, or patient condition)

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18 hours ago, gagpinks said:

Hi All

My manger has decided to send all positive DAT( even if it's weak positive ) to reference lab for elution if patient has been transfused in last 28 days. Is it really necessary to perform elution when there's no sign of haemolysis ? Is there any guidelines to follow for investigation of positive DAT. 

 

In my opinion, this very much depends upon the underlying pathology.  For example, if the patient has an auto-immune haemolytic anaemia, the chances are very strong that the DAT will be positive before as well as after the transfusion, and that any eluate will be positive with all red cells tested (of normal type).  The chances of detecting a new antibody specificity on the DAT positive red cells under these circumstances is disappearingly small.

Therefore, if the sample is sent to a reference laboratory on a regular basis, your manager will be 1) showing a degree of ignorance that should be surprising, 2) will be upsetting the staff of the reference laboratory, as most have enough to do, without having to perform extra, unnecessary work, and 3) as you are in the UK, will be wasting the tax payer's money (and, as a UK tax payer, I feel very strongly about this).

If, on the other hand, the positive DAT is new, then a reference laboratory would be delighted to help out.

Of course, what your manager could do is to buy his/her own laboratory an elution kit, and train his/her staff to use it!!!!!!!!!!!!!!!!  This may bring the cost of the kits to meaningful results ratio to the overall pathology manager, which could be of interest!

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A blanket policy like the one gagpinks describes will result in a lot of clinically irrelevant testing (as Malcolm so elegantly stated). Having a policy is a good idea, but it must be applied with precision, on a case-by-case basis.

An eluate may be relevant if there's clinical or laboratory evidence of a transfusion reaction. I've heard of policies where a significant change in the strength of a post-transfusion DAT triggers preparation of an eluate. However, as Malcolm also points out, such eluates in persons with "warm-autos" are almost useless, unless one is prepared to perform adsorptions on the eluates to look for alloantibodies behind the auto.

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3 hours ago, Malcolm Needs said:

In my opinion, this very much depends upon the underlying pathology.  For example, if the patient has an auto-immune haemolytic anaemia, the chances are very strong that the DAT will be positive before as well as after the transfusion, and that any eluate will be positive with all red cells tested (of normal type).  The chances of detecting a new antibody specificity on the DAT positive red cells under these circumstances is disappearingly small.

Therefore, if the sample is sent to a reference laboratory on a regular basis, your manager will be 1) showing a degree of ignorance that should be surprising, 2) will be upsetting the staff of the reference laboratory, as most have enough to do, without having to perform extra, unnecessary work, and 3) as you are in the UK, will be wasting the tax payer's money (and, as a UK tax payer, I feel very strongly about this).

If, on the other hand, the positive DAT is new, then a reference laboratory would be delighted to help out.

Of course, what your manager could do is to buy his/her own laboratory an elution kit, and train his/her staff to use it!!!!!!!!!!!!!!!!  This may bring the cost of the kits to meaningful results ratio to the overall pathology manager, which could be of interest!

I agree with you Malcolm! ! The way we are sending sample to reference lab, I feel like to buy elution kit. But it's their any guidelines on Positive DAT where I could convince my boss.   My understanding is to send sample to reference lab if there is strong indication of transfusion reaction or HDFN. 

 

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  • 5 months later...

If patient had transfusion in last 28 days and if DAT is positive I understand we have to perform elution to find out wheather is there any clinical significant antibody present. 

But if patient is on regular transfusion  (not AIHA) and DAT is positive do we still have to send sample to reference lab for elution eventhough elution is done within 28 days. 

For eg : If patient had transfusion last 28 days.current DAT is positive, sample sent to ref lab for elution : no antibody detected. 1 week later patient need transfusion but DAT is positive. Is it still necessary to perform elution eventhough elution is performed 1 week ago.( No sign of haemolysis in this case).

My manger thinks when there is DAT positive patient is on regular transfusion we have to perform elution every time patient need blood. 

I am still confused when to perform elution?  

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I don't want to get you into trouble, but I would suggest that you gently persuade your manager to either read (and take notice of) BSH Guidelines or (or better still, and) contact an NHSBT Consultant to get advice/contact one of the writing group of the Guidelines (medically qualified, if necessary) to save him/her and his/her staff a lot of totally unnecessary work and expense (particularly as his/her budget is provided by British tax payers, of which I am one)!!!!!!!!!!!!!!!!!   :angered::angered::angered::angered::angered:

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Interesting topic.  In just a few posts, it is easy to see there is a variety of ways labs approach the "how often are elutions performed" question and under what circumstances.  I too agree with Malcolm; in the presence of AIHA and a positive DAT, most likely you will get off a panagglutinin every time you perform an elution.  Once this occurs, there is no point in performing additional elutions on a routine basis.

In the patient though who has a positive DAT and is transfused on a regular basis, and has a negative eluate (yes, this does occur) the elution question is a bit different.  Technically, any transfusion can result in the production of an alloantibody that may or may not present itself in a hemolytic fashion.  It is possible to have a "delayed serologic transfusion reaction" that shows no signs or symptoms of a hemolytic process. In this scenario, the idea of not doing an elution on a regular basis because it has never revealed anything in the past, may result in missing a newly formed, clinically significant antibody that is only detectable in the eluate.  Not performing an eluate in this scenario is not without risk and should not ever become "policy" without proper overview of the clinical situation.

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On ‎3‎/‎21‎/‎2017 at 4:54 PM, StevenB said:

Interesting topic.  In just a few posts, it is easy to see there is a variety of ways labs approach the "how often are elutions performed" question and under what circumstances.  I too agree with Malcolm; in the presence of AIHA and a positive DAT, most likely you will get off a panagglutinin every time you perform an elution.  Once this occurs, there is no point in performing additional elutions on a routine basis.

In the patient though who has a positive DAT and is transfused on a regular basis, and has a negative eluate (yes, this does occur) the elution question is a bit different.  Technically, any transfusion can result in the production of an alloantibody that may or may not present itself in a hemolytic fashion.  It is possible to have a "delayed serologic transfusion reaction" that shows no signs or symptoms of a hemolytic process. In this scenario, the idea of not doing an elution on a regular basis because it has never revealed anything in the past, may result in missing a newly formed, clinically significant antibody that is only detectable in the eluate.  Not performing an eluate in this scenario is not without risk and should not ever become "policy" without proper overview of the clinical situation.

To bounce off what you're saying, I don't think I've seen any studies that looked at an increased rate of "informative eluates" based on changes in the DAT strength since last testing.

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1 hour ago, goodchild said:

To bounce off what you're saying, I don't think I've seen any studies that looked at an increased rate of "informative eluates" based on changes in the DAT strength since last testing.

The nearest I have seen to this is:

Sachs UJH, Roder L, Santoso S, Bein G.  Does a negative direct antiglobulin test exclude warm autoimmune haemolytic anaemia?  A prospective study of 504 cases.  British Journal of Haematology 2006; 132: 651-661 (DOI: 10.1111/j.1365-2141.2005.05955.x).  Don't be fooled by the title of the paper, as the paper does go into this, but only briefly.

In such cases, we used to gauge to see if the intervals between transfusion episodes were getting shorter, suggesting that a "new" antibody may be present, but this also depended on the doctors looking after the patient remaining the same (brand new doctors out of medical school tend to be a bit more enthusiastic about ordering transfusions, until they are tamed!).

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  • 3 years later...

We performed elutions when the DAT is positive in IgG and the patient has been transfused in the last 14 days. There could be a rare instance that we would do an elution anyway but I can't recall a time that we felt it was indicated.

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