We recently had a female teenage patient that was previously reported from an outside hospital to have a WAA, CAA and low incident allo antibody (not identified) about a month before being sent to us.  The original hospital blood bank was gracious enough to send the ABO genotype report from New York Blood Center which showed the patient is type B but nothing regarding Rh (D) typing or antibody identification.  Both our gel and tube ABORh reactions had positive controls and were completely inconclusive (we tried washed and prewarmed as well).   Our gel screen and LISS screen were 4+ positive as well.  We sent to our IRL for workup and it came back with WAA,  no underlying allo, and they had to DTT treat the cells to come up with the ABORh of B pos.  We decided to result our ABO as NTD (no type determined) and Rh as IND (indeterminate) and have instructions to give least incompatible (DAT IgG and auto control both 4+ so anything less than 4+ is considered least incompatible) type O pos or O neg RBCs for transfusion.  Luckily she didn't need transfusion during this admission but I'm questioning my own logic.  We can't determine the ABO or Rh type but we also can't determine the WAA so we rely on the results from our IRL to result the ABID.  Should we also rely on the IRL for the ABO and Rh result, change the patient's type to B POS, and give least incompatible type B POS (instead of using type O) if necessary?  Can we rely on one Rh type from our IRL to give Rh positive RBCs and platelets?  She's now being seen in our hematology clinic weekly.  

With all due respect, if you do not trust the results given to you by your IRL, why did you send samples to them in the first place?

The other thing is that the term "least incompatible" has been "rubbished" by LaTwrie Petz almost 20 years ago now (and you can't get much better than him!) - see Petz LD.  "Least incompatible" units for transfusion in autoimmune hemolytic anemia: should we eliminate this meaningless term?  A commentary for clinicians and transfusion medicine professionals.  Transfusion 2003; 43(11): 1503-1507.  DOI: 10/1046/j.1537-2995.2003.00583.x.

I apologise if this reads as I am being personally rude to you; that is DEFINITELY NOT my intention.

We always felt that least incompatible is like saying someone is a little pregnant . . .

The classic WAA case - an autoantibody that prefers the presence of a normal e antigen on its target red cells. May or may not be compatible with e- (R2R2) cells, but often shows weaker reactivity, especially in it's early stages of development. By the time the autoantibody gets to the 4+ stage (complete, solid agglutination), there are rarely any weaker cells.

The question: Do you transfuse e- (R2R2), i.e., the "least incompatible" ?

From a rarity/inventory point of view, in the short term that may be manageable, but probably unsustainable long term. The decision gets more complicated when the patient is E-. One could argue that there's a significant chance that by transfusing "double-dose" E+ cells, you'll cause the patient to make anti-E. Oops. Next time around, the R2R2 option may be off the table.

And ultimately, as Petz opines, there's scant evidence to support that "least incompatible" cells (e- in the above case) survive in vivo any better than random cells.

By any chance did the Reference Lab perform any other antigen typing?  Sure, you can't get Kell typings from a DTT Treated Cell, but what about the others?  Having that information would helpful with the decision to transfuse 'antigen-negative' (yes, 'least incompatible' evokes a false sense of security).

I vote to trust the Reference Lab/DTT Treated Cell testing and call her B Pos.  You say she has a Warm AutoAntibody (of Undetermined Specificity, I assume) ... is the 'thermal amplitude' so wide that it is interfering with the Room Temperature backtype as well?

I can't help thinking about some of those 'panagglutinin' situations.  Am I running off the field with those thoughts?

22 hours ago, Malcolm Needs said:

With all due respect, if you do not trust the results given to you by your IRL, why did you send samples to them in the first place?

The other thing is that the term "least incompatible" has been "rubbished" by LaTwrie Petz almost 20 years ago now (and you can't get much better than him!) - see Petz LD.  "Least incompatible" units for transfusion in autoimmune hemolytic anemia: should we eliminate this meaningless term?  A commentary for clinicians and transfusion medicine professionals.  Transfusion 2003; 43(11): 1503-1507.  DOI: 10/1046/j.1537-2995.2003.00583.x.

I apologise if this reads as I am being personally rude to you; that is DEFINITELY NOT my intention.

Hi Malcolm,

What terminology is recommended in these situations? We have always used "least incompatible" in the states. I think, probably, the majority of our databases have that option listed besides "compatible" and "incompatible." What terminology should replace "least incompatible?"

Edited February 10, 20223 yr by jayinsat
punctuation error.

14 minutes ago, jayinsat said:

Hi Malcolm,

What terminology is recommended in these situations? We have always used "least incompatible" in the states. I think, probably, the majority of our databases have that option listed besides "compatible" and "incompatible." What terminology should replace "least incompatible?"

We used and continue to use:  INCOMPATIBLE. 

12 minutes ago, jayinsat said:

Hi Malcolm,

What terminology is recommended in these situations? We have always used "least incompatible" in the states. I think, probably, the majority of our databases have that option listed besides "compatible" and "incompatible." What terminology should replace "least incompatible?"

In England, where most cross-matching for these cases is performed by the NHSBT, usually using plasma post-allo-adsorption, we always used the term "suitable for".

To all, we use Least Incompatible because that's what the physicians understand.  The result is incompatible and a signed waiver from Standard Protocol is required by the MD prior to transfusion.  No further antigen typing was reported in the preliminary report by our IRL and the patient was recently transfused.  There transfusion recommendations are for type compatible, least reactive with patient serum/plasma and to order a red cell genotype (NGS).  We do not routinely have the IRL complete crossmatches with their adsorbed plasma but I could order it.  I will update our chart to accept the ABO and Rh with B POS, I was just leery because of the report from the outside hospital being incomplete.    

As Malcolm posted if you don't believe the IRL results why send it. The IRL gave you a B pos result, which aligns with the other history you obtained. That being said your policy may need to be scrutinized to determine if the B pos result is valid for the entire admission or needs to be confirmed for each new sample. I would suggest getting this clarified for future admissions, get your pathologist involved as they may have strong opinions on this and once clarified document clearly in your LIS the process.

For those who call these units 'incompatible' and transfusing them, what does the wording in your waiver say? I assume you are not just issuing "incompatible" units without some kind of deviation form. Please help us out; those who are still using the rubbish term "least incompatible", to start discussions on what kind of language to use. Here are some terms I recall from older posts about this subject, please refresh my memory as these are the only ones I can remember so far. Thank you in advance for any help.

1. Suitable for.

2. Serologically compatible.

3. Most compatible.

Mine states the units are incompatible and gives the reason for the incompatibility.  

I like “Reactive”, though we use “least incompatible”. I think change is the issue as the the questions about meaning would last years!! 

We issue units for warm auto cases as 'incompatible, approved by pathologist'. We enter a comment in the patient Blood Bank record with the date/time we got the approval, from whom, and documentation of any instructions they give and any instructions we are asked to pass on to nursing. In some cases, the pathologist may consult with the ordering provider and request that he/she sign a 'Request for Release' form with one of two options selected:

- incompatible units due to clinically insignificant interference (cold agglutinin, rouleaux, etc.) OR

- incompatible units due to interference from a clinically significant warm reacting autoantibody. Although some units may appear compatible in vivo, it is impossible to rule out any underlying clinically significant alloantibodies that may cause a hemolytic transfusion reaction.

The pathologist may also sign the release form in some cases, if requested by the provider.