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Frequency of Antibody Identification


SRTECH

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Forgive me if this has been adressed before...:redface:

At the hospital where I work we repeat Antibody Id's as follows:

1. Pregnant Patients : Every three days.

2. Warm Autoantibodies : If patients have been transfused after last ABID- every 7 days.

3. All other patients : every 30 days if there is no increase in strength of antibody reactivity or appearance that

there is a different antibody present than what was previously identified.

My search of the AABB Technical manual did not result in any time frame that I could find.

How often do you do the above?

Thanks for your anticipated responses!

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Not sure if I get what you mean by Antibody ID. If you mean to completely ID a known antibody, the more important thing is to rule out any new antibodies that have developed since the last screen/ID.

If that is what you are asking, we repeat all "IDs" after the last screen/ID for a particular specimen expires -- every 4 days. Even if the patient has not been recently transfused (or pregnant in the last 3 mos). Your:

". All other patients : every 30 days if there is no increase in strength of antibody reactivity or appearance that

there is a different antibody present than what was previously identified."

confuses me, how can you tell if there has not been another antibody developed unless you do a panel to ID what is there?

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"confuses me, how can you tell if there has not been another antibody developed unless you do a panel to ID what is there"

Per my Blood Banks Policy· When the current antibody screen is positive and an antibody identification has been performed within the last 30 days and there is no increase in strength of antibody reactivity or appearance that there is a different antibody present than what was previously identified, antigen negative units must be crossmatched without further antibody identification work. (Exception: When the patient has demonstrated a warm autoantibody and the screen is positive antibody identification must be performed every 7 days if patient was transfused after the last workup).

.

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Yeah, that seems confusing to me. It seems like it is saying to check for a change in AB strength or reactivity pattern (which you would have to do a panel to determine) and at the same time that you do not have to do an AB ID.

Again, once a certain amount of time has passed, there is no way to determine if another AB has developed without doing another screen, and if the screen is positive (which it will be in the case of a patient with a previously ID'd AB), you would have to do a panel to determine whether or not anything new is present. (you can't just say that there is nothing new developing because the AB screen is simular to a previous one).

Is it possible that the procedure is wrong? Or am I totally missing something here?

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We perform the ID every time the previous sample expires (or when the patient next comes, if longer). We do not re-identify known antibodies, although we do run one cell each to determine if they are still demonstrating. This is mainly to report correctly. Each ID report states only the antibodies currently demonstrating. The pre-existing antibodies are listed with the patient's administrative file.

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I agree with SMiller and Julie. We repeat the AbId when the asmple has expired (and a transfusion is requested). You cannot depend on the strength and pattern of the AbSc to tell if a new Ab has appeared as it may take the same pattern and strength in the Screen as the previous antibody(s). We do repeat the AbSc and I like to because the pattern and strengths are good to look at BUT not to make a major decision on.

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At my place we repeat a full panel every 7 days unless crossmatches against antigen neg blood are reactive, or it's obvious something is different from the antibody screen. However, when I've polled hospitals in my area (central Michigan) the answers go from "every 3 days" to "every 30 days".

Don

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I agree with SMiller and Julie. We repeat the AbId when the asmple has expired (and a transfusion is requested). You cannot depend on the strength and pattern of the AbSc to tell if a new Ab has appeared as it may take the same pattern and strength in the Screen as the previous antibody(s). We do repeat the AbSc and I like to because the pattern and strengths are good to look at BUT not to make a major decision on.

We so the same as Liz, SMiller & Julie, etc (ie: with each new specimen, which is good for 3 days after the date drawn.)

I know that some institutions use the "if similar strength and pattern of previous antibody screen" policy, but I don't feel comfortable with that. A different lot # of Antibody Screening Cells may demonstrate different strenths of antigens, testing techniques and grading can vary between technologists, etc.

Donna

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Another way that those that don't repeat IDs on each new specimen detect evidence of new antibodies is incompatible AHG xms. Also, if the known antibody is K and both screen cells react, you have evidence of a new antibody.

We do a full ID on every new specimen (3 days) because I can't break the habit of my techs running all of the panel cells they know will be positive. Instead I would only run those that will tell them about new antibodies and maybe one expected positive to confirm reactivity. With automation coming, I think we are stuck with running all panel cells every time so I haven't pushed hard for change.

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I still think that relying on the cross-match to detect de novo antibodies is potentially dangerous.

As I've said before, screening cells are chosen because of their phenotype, with all important antigens that show dosage having probable homozygous expresion (many, demonstrated either by molecular techniques, or by flow cytometry). In addition, these cells are in a preservative that is designed to keep the antigen strength at an optimum level, without worrying about keeping the oxygen carrying capacity at an optimum level.

On the other hand, the red cells in a unit can be of any phenotype (often unknown). These cells are in a preservative designed to keep the oxygen carrying capacity at an optimum level, without worrying about keeping the antigen strength at an optimum level.

If, as you say Mabel, there is already an anti-K present, and your K+k+ screening cell happens to be the cell that is also Jk(a+b-), and the patient makes an anti-Jka that is showing dosage, are you certain to detect this in the cross-match? Answer - NO!

Is this dangerous? Answer - judging by the results of the various haemovigilence schemes around the world - YES!

:omg::omg::omg::omg::omg:

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We perform the ID every time the previous sample expires (or when the patient next comes, if longer). We do not re-identify known antibodies, although we do run one cell each to determine if they are still demonstrating. This is mainly to report correctly. Each ID report states only the antibodies currently demonstrating. The pre-existing antibodies are listed with the patient's administrative file.

This is what we do. Does not matter what the AB is.

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The minimum regulations in the US allow not repeating the ID unless there is evidence of new antibody. I agree that I want to run cells on every patient that are as good at detecting the usual antibodies as my screening cells are in a patient with no antibodies so I don't subscribe to the above approach, but it is "legal" and last I knew I think U of Michigan followed this approach.

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I would not be able to sleep at night if I didn't at least do a rule out panel. I've seen too many examples of a negative antibody screen upon admission and a week later have an anti-Jka show up post transfusion.

If you know the patient has an antibody, run a selected panel of cells that are negative for the corresponding antigen so that the only reactions you get would only be from something new.

To me, this is equivalent to techs who think that because the reactivity of a panel matches perfectly with one antibody, they don't need to rule out anything that may be underlying.

Just my 2 cents. Happy thanksgiving.

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Srtech, that's what our BB policy states as well, and the AABB manual says each facility should define and validate policies for the detection of additional antibodies. But this discussion has certainly brought up some "food for thought" and I may be looking at changing our policy. I do think the idea of not re-identifying the original antibody is valid, and cells should be selected to reflect that thought.

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We have been using this for the last few years without any problems:

For patients who have a history of previously identified antibodies, it is not necessary to repeat the antibody ID when they come back for subsequent transfusions, provided that ALL of the following conditions are met:

1) The antibody screen fits the history. For example, if the patient previously had Anti-K and Anti-E, the screen cells that are positive for E or K are currently positive, and the screen cells that are E neg K neg are not reacting.

2) Donor units are phenotyped negative for the patient's antibodies. In the above example the donor units must be negative for both E and K.

3) The phenotyped donor units are crossmatch-compatible at the Coombs phase as well as immediate spin compatible.

Reference:

W J Judd, S H Butch, Repeat Antibody Identification Studies: How Much Is Enough?, Transfusion, 2002—Vol. 42, Supplement.

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1) The antibody screen fits the history. For example, if the patient previously had Anti-K and Anti-E, the screen cells that are positive for E or K are currently positive, and the screen cells that are E neg K neg are not reacting.

So, for example, take a patient with anti-D. Patient has lived in the area since their first cord blood sample at birth so full transfusion history. Patient comes back for a transfusion for a.n. reason and the 3 cell screen is strongly exhibiting a reaction in the first two cells of your 3 cell screen. How do we know that the patient hasn't had a transfusion elsewhere and developed anti C and E? Even patients with a full history sometimes get transfused elsewhere - hence our patient with an anti-f :(

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We use a 3-cell screen (Immucor ECHO)

Well then, unless one of those screening cells is E+, K+, and the other two E-, K-, you will be relying on one screening cell to ensure that no other antibodies have been produced. How would you detect an anti-Jka, for example, if this one cell were Jk(a-b+), or anti-Jkb, if that one cell were Jk(a+b-)? The same allplies for other clinically significant antibodies, such as anti-S, or anti-s, does it not? Or am I missing something here?

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Malcolm, #3 of dmpollock's post indicates that, as is required by the AABB in the US, all units of blood set up the a patient with a known antibody will have to be AHG cross matched. This, in a sense, could give any number of additional "antibody screening cells". If any of them are incompatible/positive then a full antibody identification regimen must be undertaken to determine why the unit(s) are incompatible. I suggest you read the paper referenced at the end of the post if you have not. In my previous life this is the regimen we followed and there were no adverse consequences resulting from it that I am aware of.

Once again I must state that much of what we practiced was driven by where our individual fears lay. There was a time when minor side crossmatching was the norm and every time 2 cells bumped into each other microscopically extensive antibody ID had to be undertaken. DATs and or Auto controls were performed on every patient every time. Over the years the pendulum of paranoia has swung to the other side based on studies, economic pressures, simply more science based information. Will it swing back, maybe, but for many it never moved and never will. I guess I'll just have to keep watching to see where it goes.

So much for my philosophical soap box for a Monday moring. :blahblah::faint:

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Malcolm, #3 of dmpollock's post indicates that, as is required by the AABB in the US, all units of blood set up the a patient with a known antibody will have to be AHG cross matched. This, in a sense, could give any number of additional "antibody screening cells".

This is an entirely unsatisfactory practice - units for crossmatch are treated for optimal oxygen carrying capacity, screening/antibody cells for optimal antigen life. A unit of blood may not have sufficient reactive antigen sites to allow reaction in vitro to occur. They are perfectly capable of illiciting an immune response though.

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