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How many times do you perform an antibody identification?


javvcr

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My latest CAP survey had a specimen that hit this topic - a sample with anti-Cw in it. The results came back with no concensus for that sample - the referees were almost as divided as the rest of us. I think it likely that the folks who found the antibody were doing AHG crossmatches on everybody and picking up the antigen positive donor. The folks who didn't find it were probably doing the AS (which was negative) with an IS crossmatch. It will be interesting to see what the 'discussion' is when the final report comes from CAP.

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:rolleyes:I wish CAP would use more realistic antibodies. Most antibody screening cells do not have the Cw antigen.

I agree with you on the second point Mary, but not the first. We often identify an anti-Cw, either on its own or in conjunction with other atypical alloantibodies, so the presence of an anti-Cw is realistic.

What is very much a moot point is whether or not anti-Cw is clinically significant in terms of haemolytic transfusion reactions. I have never seen a convincing case.

As far as I am aware, there is only one paper in the literature that implicates anti-Cw in haemolytic idsease of the foetus (as opposed to haemolytic disease of the newborn) and this case was never sent to a Reference Laboratory for independent verification, but was diagnosed at the hospital (And no, I am not decrying hospital laboratories. All I am saying is that independent verification is always worthwhile from a scientific point of view).

:)

Kollamparambil TG, Jani BR, Aldouri M, Soe A, Ducker DA. Anti-Cw alloimmunization presenting as hydrops fetalis. Acta Paediatrica 2007; 94; 499-501.

Edited by Malcolm Needs
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I also had this CAP Survey (one sample had Anti-Cw and another sample had Anti-A1), but what I was unhappy about was how to report our findings. (Should we report a Neg Ab Screen, but report the antibody in the Ab Identification section???) I finally called CAP for clarification.

I was told that if you report "Unexpected antibody not detected" in the Ab Screen section, their computer will grade your answer as "Incorrect" if you also report any antibody in the Ab Identification section. (Then, I was told that you are supposed to write an explanation that you identified Anti-XXX in the "Other" section at the end of the report form.)

It was obvious that they were not going to get a consensus for the results, because CAP's computer was not capable of recognizing the correct answering combinations ("Neg" Antibody Screen results and "Anti-Cw" or "Anti-A1" in the Antibody Identification results) or recognize the correct answers if the Lab did Electronic Xmatches or Immediate Spin-Only Xmatches ("Neg" Antibody Screen results, "No antibody detected" Antibody Identification results, and "Compatible" Xmatch results.)

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Hold on to your seats because most of you aren't going to like this but.....

If we had ID'd an antibody, let's say anti-K for discussion purposes, in the past (how far in the past is not relevant), we would do an antibody screen on the current specimen, it the screen is positive only for anti-K and the AHG x-m is compatible with K negative units we do no additional testing. This is in full compliance with AABB Stds (I don't have a copy with me to quote chapter and verse).

:faint:

Well, as far as it following the Standards, I would say "yes and no." You are covered for following the Standards by performing an Antibody Screen every 3 days (and looking for changes); and you are not the only Institution to just look for a "change" in reactivity to determine whether another work-up needs to be done. However, the way the Standards actually word it in 5.13.3.3 "In patients with previously identified clinically significant antibodies, methods of testing shall be those that identify additional clinically significant antibodies. I can tell you that I have seen this scenario a number of times: Same cell(s) reacting as previously identified antibody(ies); crossmatch compatible; patient transfused. Next specimen, positive DAT because the "new" antibody was on the same cell(s) as the old, and is only reacting with homozygous expressions of the Antigen. Had it at my current Insitution several months ago on a patient with a historical Anti-c, who made an Anti-Jka which was on the same cells as the c, and was only reacting with homozygous cells.

Now in saying that, I do also acknowledge then that if you are not running at least a select cell panel with every specimen (every 3 days), then you still have this risk (i.e. in a phone poll I did in my local area last year, the majority of Institutions only run a new panel every 7 days and some Instittuions longer.

So, going back to the Standard, are we "really" complying if not running select cells every 3 days (which I can say I don't do; but given these scenarios, it is taking a risk).

Brenda Hutson, CLS(ASCP)SBB

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I also had this CAP Survey (one sample had Anti-Cw and another sample had Anti-A1), but what I was unhappy about was how to report our findings. (Should we report a Neg Ab Screen, but report the antibody in the Ab Identification section???) I finally called CAP for clarification.

I was told that if you report "Unexpected antibody not detected" in the Ab Screen section, their computer will grade your answer as "Incorrect" if you also report any antibody in the Ab Identification section. (Then, I was told that you are supposed to write an explanation that you identified Anti-XXX in the "Other" section at the end of the report form.)

It was obvious that they were not going to get a consensus for the results, because CAP's computer was not capable of recognizing the correct answering combinations ("Neg" Antibody Screen results and "Anti-Cw" or "Anti-A1" in the Antibody Identification results) or recognize the correct answers if the Lab did Electronic Xmatches or Immediate Spin-Only Xmatches ("Neg" Antibody Screen results, "No antibody detected" Antibody Identification results, and "Compatible" Xmatch results.)

Yes! We stressed over how to report this one for several days. We also called and were told to use the "other" section. I haven't received my results yet from the pathologist, but hopefully we conveyed our answers correctly! We do electronic crossmatching, so of course we just performed immediate spin on the CAP, so we most definitely did not get the anti-Cw. I wonder if they included the anti-Cw to prove some point for electronic crossmatching??

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I also had this CAP Survey (one sample had Anti-Cw and another sample had Anti-A1), but what I was unhappy about was how to report our findings. (Should we report a Neg Ab Screen, but report the antibody in the Ab Identification section???) I finally called CAP for clarification.

I was told that if you report "Unexpected antibody not detected" in the Ab Screen section, their computer will grade your answer as "Incorrect" if you also report any antibody in the Ab Identification section. (Then, I was told that you are supposed to write an explanation that you identified Anti-XXX in the "Other" section at the end of the report form.)

It was obvious that they were not going to get a consensus for the results, because CAP's computer was not capable of recognizing the correct answering combinations ("Neg" Antibody Screen results and "Anti-Cw" or "Anti-A1" in the Antibody Identification results) or recognize the correct answers if the Lab did Electronic Xmatches or Immediate Spin-Only Xmatches ("Neg" Antibody Screen results, "No antibody detected" Antibody Identification results, and "Compatible" Xmatch results.)

I think that you all have every right to complain.

These exercises should be there to test your serological prowess, not your ability to fill out a form, either electronically or by hand.

:eek:

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I'll confess I've never been trained to selectively panel from the positive antibody screen. We run a primary panel (usually 11 cells (CSL) or 16 cells (Immucor) with known multiples), then select cells to knock out knowns, prove likely ones (definite neg for known, or dosage with known, pos for suspected).

In our previous system also, we would report history of anti-X and then anti-Y detected in this sample, so we would have to demonstrate the disappearance of a known antibody if that was the case.

I'll add to that we never use the patient's sera to verify antigen negative status, every unit we receive must be pheotyped to confirm antigens by guidelines, regardless of the information provided by ARCBS.

I would agree with SMW that you do not need to re-identify known antibodies, particularly if you are not relying on a compatible crossmatch for transfusion purposes (which for reasons previously mentioned, I do not feel comfortable doing anyway). What would be the benefit of proving the antibody(ies) is still there, or that it has disappeared? It does take a little time to create your select cell panel, but once you do it awhile, it can be quick. By using a select cell panel and not re-identifying previously identified antibodies, your work-up can take much less time.

Brenda Hutson, CLS(ASCP)SBB

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So if a patient has a history of an anti-e, you run a 16-cell panel (of which 14-15 cells are likely e-positive), you now have maybe 1 or 2 results (from the e-negative cells) that have provided you any useful information? That's what makes blood bank serology so interesting...you have to think before you leap. It doesn't make sense to waste tech time and facility reagents/money, let alone wasting patient sample, by performing testing that provides no value and does not change the type of product selected for transfusion. Why not report history of anti-X, no additional antibodies detected? You're still going to select X-negative units and perform a serologic crossmatch but perhaps only needed to test a few panel cells.

As a second comment, the regulations do NOT require units to be tested with a reagent antisera to determine they are antigen negative. The regs (e.g., AABB 5.14.3) state units "...shall be prepared for transfusion that do not contain the corresponding antigen and are serologically crossmatch-compatible." The standards do not specify the method or HOW you make the determination the units are antigen-negative or even who does that testing. So if you determine the patient's serum is reacting at X-strength with a single dose expression of a particular antigen and you test that unit with the patients serum, you complied with both requirements (antigen neg and xmatch) with only one test. Think of it as an analogy to antibody detection. The regs state methods of testing shall demonstrate clinically significant antibodies but they do NOT specify what those methods are---you get to decide (and provide supporting rationale if necessary). The same for crossmatch, ABO typing, infectious disease testing, ...... Testing with reagent antisera may be your selected method to determine that a unit is antigen negative and comply with the regs, but please do state that is the requirement or imply that is the only acceptable method to meet the requirement.

Again, from my perspective, Anti-Jka is one good example of why this is risky; at least if you use Gel. I have seen quite a few Anti-Jka antibodies that not only reactive with homozygous cells only, but do not even react with "all" homozygous cells. (I posted a previous Thread on that). So again, from my persepctive, it is a risk to rely on a compatible crossmatch for transfusion purposes.

Just where I am coming from; don't mean to put anyone else down who does it differently.

Brenda Hutson, CLS(ASCP)SBB

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For a single antibody, we would run a primary 11 cell panel, and the CSL's are good at separating out Rh antibodies particularly, not so terrific as things get more complicated. The 16 cell panel we use when the patient has multiple antibodies, otherwise it's generally used for selective panelling, after the primary panel.

We can't say something has disappeared if we haven't proved it - especially if our screening cells don't necessarily demonstrate the disappearance because the "new" antibody can be positive in at least one cell that crosses with the "old" antibody. I will say what we now do is only report an anything new and the other information is available in the LIS, but our testing practice has not changed.

And, I'm Australian:

The ANZSBT guidelines 2.2.2.1: "Red cells should be selected which are negative for the relevant antigen where the antibody is clinically significant [Table 1]. Antigen typing should be confirmed by the laboratory performing the pretransfusion testing." Table 1 lists by clinical significance, obviously.

Using the patient's serum is not an accepted method of confirmation of antigen-negative status.

You can quibble on the use of should up there, but GLP dictates that "should" in this instance means "must" - everyone makes mistakes, even the ARCBS.

One thought I had in reading your post. I have seen a number of instances where antibodies are mis-identified because they are on the same cells as the known antibodies. This can especially be a problem with less experienced Blood Bankers. I learned a system a long time ago that I have since made Techs. in every Insititution I work at, follow; even in a Reference Lab (because of a couple of incidences of reporting a new antibody that was not in fact there). What I do is in the right hand column of the rows tested, I will put the phenotype of the known alloantibody(ies); for example, if a patient has Anti-E, Anti-c and you are trying to prove or rule-out Anti-K now, I might write: E+c-K+ in one of the rows. Otherwise, less experienced Techs. might look at the fact that all of the K+ cells are positive, and conclude the patient has an Anti-K, without taking into consideration known alloantibodies.

To prove something, they are required to have 3 cells which are positive for the new suspected antibody, but negative for the others. And on an initial work-up, same thing; write antigens in the rows, depending on what you suspect is there; must have 3 for each antibody, which are negative for the others.

Brenda Hutson, CLS(ASCP)SBB

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Our current policy follows (with reference). I would like someone from U Mich to verify, but I believe their practice is the same as below. Note, not applicable for warm autoantibodies.

-------------------------------------

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.

And what about the possibility of new antibodies being under the previously identified? You cannot always expect a change in strength when that happens. As I mentioned earlier, we had this happen with an Anti-Jka. The patient had a previously identified anti-c. The 2 Jka screening cells were also the c+ cells; no change in strenth. Next work-up, it was a new lot# of screening cells and Jka was on cell I this time (so c-). And by then, we also had a lovely positive DAT to go along with it!

Brenda Hutson, CLS(ASCP)SBB

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In the UK, a patient is not eligible for electronic issue if a clinically significant atypical alloantibody has every been detected in their plasma, so this would not be an issue (unless, of course, the patient switches hospitals, forgets to produce their antibody card and the antibody is no longer detectable, and then they are a candidate for an anamnestic response).

However, am I correct in thinking that you are referring to an antibody directed against a low incidence antigen here John, where the antigen is almost certainly not going to be expressed on the screening red cells? If so, that is a slightly different situation, because you are much less likely to come across, for example, a unit that is both K+ and Wr(a+) (although, of course, it can happen) than one which is K+ and Jk(a+) (to use Donna's example).

Even then though, there was a paper/editorial written some years ago now by George Garratty entitled something along the lines of "Do we need to worry about low incidence antigens" (I don't think that is by any means the correct title, but it was something like that) in which he showed amthematically that there was very little chance of a unit of blood expressing a low incidence antigen being given to a patient by electronic issue, who had an antibody directed against this same antigen, and it being strong enough to cause anything more than a minor delayed haemolytic transfusion reaction, resulting in a little jaundice and a requirement for re-transfusion as the red cells are removed from the circulation.

If I can find the actual reference amongst the detrius on my desk here at home, I'll post it.

:)

When I have worked places with Electronic XM, patients with known alloantibodies do not qualify; they must have a AHG crossmatch performed. And again, as I responded in many e-mails now, I think there is a risk in not screening units. As far as low Incidence antibodies, I guess my thought is that there are 2 things accomplished by performing a AHG crossmatch on patients with known alloantibodies: picking up incorrect antigen typing results, and catching antibodies to Low Incidence antibodies in a patient who is a known "antibody producer."

Just my thoughts...

Brenda Hutson, CLS(ASCP)SBB

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Hey all!

We do a new workup on a patient every three days, unless it is a surgical patient who's qualified for "preadmit" antibody screens which lasts 14 days. I wish we'd do this where I currently work, but where I used to work, we would run a selected cell screen for patients who have previous known antibodies. We would also run a cell positive for the known antibody to see if it is still reactive. If the selected cell screen is negative, then we know that the patient hasn't developed any new antibodies. Depending on what the antibody is and whether or not it is currently reactive, we would perform either an immediate spin or AHG (gel) crossmatch.

Where I am working now, we do not have a way to bill for a selected antibody screen yet, so we are running a regular 3-cell screen and then a selected panel if we get positive reactions in the screen.

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Good point Donna and nope, you understood correctly. The theory is that if the antibody screen does not indicate a "new" antibody and all antigen negative units are AHG x-m compatible the odds are greatly in your favor that you are safe to transfuse. If I remember correctly this was first put forward by John Judd and the University of Michigan Blood Bank.

Do you perform immediate spin x-ms or electronic x-ms? If so aren't you worried about the possibility of an antibody that's not on you screening cells? Same basic idea.

I think the most recent CAP survey is a good example of John's point. If you did not have Cw on your screening cells, you did not identify the antibody. If your policy includes performing immediate spin or electronic crossmatch in the absence of antibodies, the crossmatch would have been non-reactive as well. We had an interesting experience with this one because we are a hospital system with 4 transfusion services. Only one performs antibody identifications and that one uses solid phase as the primary method. The other three use tube as the primary method. As it turns out, the solid phase screen had Cw on it, but the tube screen did not. So, our big hospital reported a positive screen, identified the anti-Cw, and got an incompatible crossmatch, but the 3 smaller hospitals reported a negative screen, no antibody ID indicated, and compatible crossmatches. What a mess!

Anyway, I think John is saying that if you get a patient with a low frequency antibody like anti-Cw, you may not detect it in the screen and you would not detect it in the crossmatch. This is a risk we take in performing either immediate spin or electronic crossmatch because we can make the assumption that we will catch all significant antibodies in the screen. This is not to say that we should go back to all Coombs crossmatching, just that this is a calculated (well sort of, I didn't do the math myself!) risk.

Was that pedantic enough Malcolm?

;)

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I think the most recent CAP survey is a good example of John's point. If you did not have Cw on your screening cells, you did not identify the antibody. If your policy includes performing immediate spin or electronic crossmatch in the absence of antibodies, the crossmatch would have been non-reactive as well. We had an interesting experience with this one because we are a hospital system with 4 transfusion services. Only one performs antibody identifications and that one uses solid phase as the primary method. The other three use tube as the primary method. As it turns out, the solid phase screen had Cw on it, but the tube screen did not. So, our big hospital reported a positive screen, identified the anti-Cw, and got an incompatible crossmatch, but the 3 smaller hospitals reported a negative screen, no antibody ID indicated, and compatible crossmatches. What a mess!

Anyway, I think John is saying that if you get a patient with a low frequency antibody like anti-Cw, you may not detect it in the screen and you would not detect it in the crossmatch. This is a risk we take in performing either immediate spin or electronic crossmatch because we can make the assumption that we will catch all significant antibodies in the screen. This is not to say that we should go back to all Coombs crossmatching, just that this is a calculated (well sort of, I didn't do the math myself!) risk.

Was that pedantic enough Malcolm?

;)

Well, I liked your answer!!!!!!!!

:):):)

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We always did a rule out panel with each new sample. There were so many times after 30 plus years that a second antibody would be there I wouldn't consider a different approach. I think it is important to help staff understand how to create a rule out panel - it was an item that I would perform competency assessment on because it is so important.

Jeanne Wall, M.Ed., MT(ASCP) SBB

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SuperMT,

I am not sure I'm understanding your reply, but do you perform immediate spin crossmatches on a patient with a previous known antibody if it is currently nonreactive?

Once a patient is known to produce an antibody, our facility, and every place I have ever worked at, always require a gel (IAT) crossmatch for the rest of that patient's life.....

Just curious...

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SuperMT,

I am not sure I'm understanding your reply, but do you perform immediate spin crossmatches on a patient with a previous known antibody if it is currently nonreactive?

Once a patient is known to produce an antibody, our facility, and every place I have ever worked at, always require a gel (IAT) crossmatch for the rest of that patient's life.....

Just curious...

Yes, I'm a little worried about this too.

As a matter of fact, we have just finished using a panel of cells that included an r"r cell with a weaker than normal E antigen. It was so weak that, in many cases it did not appear to react by IAT with examples of anti-E in pregnant women that other examples of r"r gave 3 to 4+ reactions by IAT (and before you ask why this cell was included - don't - we didn't produce the panel!). It does demonstrate, however, that relying on a single example of a red cell is highly dangerous.

:eek:

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We do identification every 14 days. It's too much work to do them every 3 days. We compare current screen results with the previous result, and perform the DAT. If there has been no significant change in the screen (a prev neg cell is now positive) and if the DAT continues to be neg, we do not run identification until after 14 days. If the previous DAT was positive, we only work it up IF the current DAT is stronger than the previous one, and that is only done IF the patient was transfused between the last DAT and the current DAT.

Hope this makes sense.

YS

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We do identification every 14 days. It's too much work to do them every 3 days. We compare current screen results with the previous result, and perform the DAT. If there has been no significant change in the screen (a prev neg cell is now positive) and if the DAT continues to be neg, we do not run identification until after 14 days. If the previous DAT was positive, we only work it up IF the current DAT is stronger than the previous one, and that is only done IF the patient was transfused between the last DAT and the current DAT.

Hope this makes sense.

YS

It makes sense. I happen to completely and utterly disagree with it, but it makes sense.

:frown::frown::frown::eek::eek::frown::frown::frown:

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If the patient is an in-patient and we know that he has not been transfused since the antibody was ID'd, we do not ID it again. We crossmatch antigen negative blood (AHG) and transfuse. If the patient has been transfused since the antibody ID was done, then we would perform antibody ID again. If the patient is an out-patient, we ID every time. We have generalists, pool, and cross-trained staff members and for us, this is the most straightfoward way to handle this.

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