Does anyone exclusivly use homozygous cells (of doseage prone ag's) in ruling out?...and ignore heterozygous cells?

[lalamb]

On panel cells that don't react w/my pateint plasma, I have been ignoring the heterozygous cells..... I don't look at them to do rule outs (Rh's, Kidd, Duffy, MNS) and only look at the homozygous cells to rule out, irregardless of the reaction strength.

Reaction strenght may review a doseage pattern, but I look at that later.

A coworker is concerned that there is no reference specifically for "ignoring heterozygous cells altogether"....just seperate references for:

• ruling out w/3 cells is optimal and ruling out w/2 cells is sometimes all you get
  
• looking at the cells w/the stronger antigen strenght, which is usually a homozygous cell for Rh's, Kidd, Duffy, MNS
  

Other thoughts ? :eyepoppin

[Malcolm Needs ☆]

I would ignore red cells that are presumed to express heterozygous antigens at your peril.

There could be a nasty little antibody specificity there that is outside the normal range of specificities that you usually see (such as an anti-Cob), that is only being expressed on these cells. Granted anti-Cob is rarely clinically significant, but it's 02.20 in the UK, and that is all I could think of as an example at the moment, and my tests are about to finish their incubation!!!!!!!!!!

Or have |I got the wrong end of the stick about your question?

[Mabel Adams]

First, you don't need to rule out with 3 pos cells. The rule of 3 is that you need 3 pos and 3 neg (or 2 and 5) to be statistically likely to be assigning the right specificity to the antibody that is reacting. You rule out several antibodies with a single cell on every negative antibody screen that you run. If it is good enough there, why should the rules change when you have a positive screen?

As for your actual question, it is also our policy on the first run through to mark off using only double-dose (homozygous) cells. It helps those less experienced in Ab ID not to have marked off something that they really still need to consider due to dosage. Once you have marked off based on the double-dose cells, you certainly may need to still evaluate the single-dose cells. You may choose to use them in marking off as well, depending on the specificity and difficulty of finding double-dose cells. Maybe strike the word "ignore" from the conversation so you make them less anxious? I don't think you need a reference to make this acceptable practice, but I think Harmening's book says to mark off only double-dose cells first. Of course, if you are trying to find 3 double-dose cells that don't react for marking off, you would be running a lot of cells. After the first marking off effort, antibody ID starts to move into the realms of art and judgment and lends itself less well to simplistic algorithms.

[Mabel Adams]

If you want to lend credence to your point of view, you can also use the Antibody ID powerpoint that is under the Educational Materials under the Library tab above. I think teachers are using it in their blood banking classrooms which means some experts support your approach.

[Malcolm Needs ☆]

I hadn't seen that PowerPoint before Mabel.

Quite simply, it is excellent.

Thank you.

(Sadly though, I don't think it's going to help me with the interesting little case that I'm working on at present!!!!!!!!!!!).

Edited February 21, 2013 by Malcolm Needs

[Mabel Adams]

Are you working night shift, Malcolm? It must be 2 a.m. in the UK!

[Malcolm Needs ☆]

I've worked all day, and am now on-call.

The one on which I am working is a sickle cell patient who (literally) walked into hospital feeling a little tired, with an Hb of 29g/L. She is known to have an auto-antibody (she certainly has!!!!), with an anti-E+Fya underneath, and has had episodes of hyperhaemolysis. Just what I want at this time of night (now just gone 3 in the morning)!!!!!!!!!!!!!!

I'm just about to see if her B cells have been "encouraged" to pop out another specificity, prior to cross-matching. I do so hope not. I'm tired and hungry, but this promises to be at least a three mug of strong coffee case!!!!!!!!!!!

[David Saikin]

There are times when all you have are heterozygous cells . . . and dosage doesn't mean they don't/won't react; just that their rxs may be weaker. Anti-M using gel is one case where many times only the homozygous cells react and gel users get used to that pretty quickly. Those M's are usually not clinically significant. Otherwise, I will use heterozygous cells to r/o when I have to.

[Joanne P. Scannell]

We do not use heterozygous cells (with few exceptions, e.g. Anti-K, -Cw, -Lua) to rule out. I have several examples of clinicaly significant antibodies that react ONLY with homozygous cells in our files.

I got validation of this concept at an AABB session in Baltimore, MD (was that 2005?). A well known reference lab mid-USA was presenting case studies and a big 'take home' was 'Do NOT rule out with 'heterozygous' cells!' In fact, be wary of ruling out with 'all' 'homozygous' cells because what may appear 'homozyous' on the panel sheet may actually be 'heterozygous' with an allele that is not tested, e.g. Fya+/Fy3 is not 'homozygous' for Fya even though it may appear that way on the panel sheet being displayed as Fya+/Fyb-.

nb I'm using semi-quotes because we are not supposed to be using 'zygosity' for expression of an antigen ... but we all do.

[Joanne P. Scannell]

What happened to the 'good old days' when we used to call the floor in the middle of the night to tell them that unless this was a life-threatening situation, the transfusion will occur during the day?

Tired patient? Go to bed, go to sleep.

Poor Malcom! How did your patient pan out? More antibodies (a responder, for sure!).

More support for transfusing 'phenotype-identical' to these frequent flyers? (Was this patient phenotyped?)

I've worked all day, and am now on-call.

The one on which I am working is a sickle cell patient who (literally) walked into hospital feeling a little tired, with an Hb of 29g/L. She is known to have an auto-antibody (she certainly has!!!!), with an anti-E+Fya underneath, and has had episodes of hyperhaemolysis. Just what I want at this time of night (now just gone 3 in the morning)!!!!!!!!!!!!!!

I'm just about to see if her B cells have been "encouraged" to pop out another specificity, prior to cross-matching. I do so hope not. I'm tired and hungry, but this promises to be at least a three mug of strong coffee case!!!!!!!!!!!

[Malcolm Needs ☆]

Well, after eight (yes, eight) cycles of alloadsorption, the auto-antibody was as strong as it was before I started, even by using pre-warmed, warm-washed LISS tube IAT at 37oC using a monospecific anti-IgG. Apart from the warm auto, she is also known to have a "cold" auto of wide thermal amplitude, together with an alloanti-E and an alloanti-Fya, and has had an episode of hyperhaemolysis.

In the end, she was given ABO and D compatible, C-, E-, S-, K-, Fy(a-b-), Jk(b-), HbS- blood, cross-matched by the "immediate spin" technique - which, of course, we could have done Before I spent 9 and a half hours working on her samples!!!!!!!!!!!!! Grrrrrrrrrrrrrrrrrr!!!!!!!!!!!!!!!!

At the same time, I also had another AIHA patient who had dropped her Hb from over 100g/L to 55g/L in about six hours. Plasma looked like mud. She's okay too, but was quite rare in that she was Ro, K+.

[jmphil4]

We require 1 homozygous cell to rule out with a few exceptions...K obviously and C and E when Anti-D is present. Any other exceptions are on a case-by-case basis.

[OxyApos]

I have solid phase/ Echo and it has similar issues like Gel. I teach new employees to only look at Homozygous cells first and see if there's a pattern etc. Basically that unlike school specimens, real patients have to be looked at as a whole with multiple scenarios and not to start crossing off every cell they can. Newly formed, low titer, etc can only show up on homozygous even if its an E and not just the notorious M and Jka/Jkb antibodies.

[lalamb]

I have solid phase/ Echo and it has similar issues like Gel. I teach new employees to only look at Homozygous cells first and see if there's a pattern etc. Basically that unlike school specimens, real patients have to be looked at as a whole with multiple scenarios and not to start crossing off every cell they can. Newly formed, low titer, etc can only show up on homozygous even if its an E and not just the notorious M and Jka/Jkb antibodies.

WE just had a pt, who had very weak rxn's...might have been a newly forming Jka. Pt had 1+ rxns on Jka homozygous and heterozygous cells...no classic doseage pattern.?????...so maybe there were 2 ab's? Tho the ref lab did say that Jka doseage may show variable expression.

M and S were initially ruled out using heterozygous cells.....I reviewed the panel using only the homozygous cells and M and S were not ruled out.

Ran a Jka-/M+, Jka-/S+ cells , which were neg...so these ab's were each ruled out w/1 cell.

Phenotyped the pt who ended up being M+, S-. Ended up crossing Jka- S- units.

By using homozygous cells to do the 1st look, I feel more comfortable that I'm getting a better (safer) picture. We will phenotype the pt for things that can't rule out. If the pt is pos...no worries. If pt is ag neg, we'll give ag neg units.

We usually have 2 indate, 16 cell panels. I have used E heteozygous cells (as they are rare), but try to include at least 1 E homozygous cell.

A lot of work but I have to sleep at night..

I appreciate all the FAST input

Edited February 21, 2013 by lalamb

[jmphil4]

Ran a Jka-/M+, Jka-/S+ cells , which were neg...so these ab's were each ruled out w/1 cell.

Phenotyped the pt who ended up being M+, S-. Ended up crossing Jka- S- units.

If you ruled out S, why did you honor it (if you don't mind me asking)?

[Joanne P. Scannell]

Lalamb ... who do you buy your panels from? I need larger panels.

[ChrisH]

I have seen a number of anti-Jka that do not react on all homozygous cells. So when I teach students, I tell them to rule out with homozygous but if the pattern does not fit then look at the ones with only one ruled out cell.

Hey I just reached my 100 post and it only took me 9 years!

[Mabel Adams]

In gel I often see anti-Jka that reacts with some double-dose cells but not all. I prefer to have 2 homozygous Jka pos cells to rule out if I can--or at least teach people to look for that pattern.

[Mabel Adams]

My conclusion from all of this is that you can have some rules of thumb as you start interpreting an antibody ID but it often moves into a realm of knowledge and judgment that you just can't write rules for.

[Joanne P. Scannell]

I agree ... instinct/training/experience has it's effects. It comes down to 'When in doubt, don't rule it out'. We have a whole set of LIS codes for 'Possible Anti- ___' because of this. And yes, they function to restrict allocation of antigen-pos/antigen-untested RBCs.

Aside from that, the basic answer to the original question of this thread is 'Do not rule out using heterozygous cells.'

My conclusion from all of this is that you can have some rules of thumb as you start interpreting an antibody ID but it often moves into a realm of knowledge and judgment that you just can't write rules for.

[SMILLER]

I agree. If you look at our procedure manual, it would say to do 3 rule outs/3 rule ins with at least one homoz for Ags that show dosage. But as discussed here, this rule cannot be hard and fast. A majority of workups are straight forward, but there are auite a few that one must be more careful with for various reasons.

We do have a helpful little chart of special notes for various Ags that have special quirks, likely phenotypes for Rh Ags, etc.

Scott

[Malcolm Needs ☆]

We do have a helpful little chart of special notes for various Ags that have special quirks, likely phenotypes for Rh Ags, etc.Scott

A helpful LITTLE chart Scott? Good Lord, if it's got all the special quirks involved with Rh, I bet it covers the entire hospital, let alone the walls of your blood bank!!!!!!!!!!!!!!!!!!!!!

:haha::haha:

That having been said (with tongue very firmly in cheek), I think that is a great idea.

[PAWHITTECAR]

Care to share your "helpful little chart"?

[ElinF]

We require 1 homozygous cell to rule out with a few exceptions...K obviously and C and E when Anti-D is present. Any other exceptions are on a case-by-case basis.

So, is it ok to rule out C and E on heterozygous cells when anti-D is present ? I always thought it was, then read somewhere that it wasn't, so we started giving E negative blood since it is alomst impossitble to rule out with homozygous. Are we doing too much work?

[Malcolm Needs ☆]

YES!!!!!!!!!!!!!!!!!!!