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Doing Rule Outs


jhaig

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I think I understand what you are trying to explain, generalist, and I agree with your logic. Let me propose two situations, and let me know if this supports your point, OK?

Situation #1:

March: Pt demonstrates Anti-c, but you cannot rule out Anti-Q (ie: doesn't matter what we name it) (Donor units for him should be c neg and Q neg.)

April: Pt demonstrates Anti-c, but you have a new lot # of panel so you happen to be able to rule out Anti-Q. (So you only have to make sure donor units for him are c neg, right?)

May: Pt's antibody screen is negative. (So you only have to make sure donor units for him are c neg.)

Situation #2:

March: Pt demonstrates Anti-c, but you cannot rule out Anti-Q. (Donor units for him should be c neg and Q neg.)

You don't see this pt in April.

May: Pt's antibody screen is negative. (My opinion is that you only have to make sure donor units for him are c neg.)

Hmmm, so in situation 1and 2 posted by L106 the anti c titer eventually drops to undetctable levels, but units selected for transfusion will be negative for c antigen, this is good. IF anti Q is also present in the March sample, maybe is has also dropped to undetectable levels by April (situation 1) or May (situation 2). I say honor it.

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And the reference lab is using expired cells to do the rule outs for you...

What exactly was CAP citing? Many institutions use expired cells to assist in rule outs. You just need to make sure the antigens are still reactive and use them together with the reactions to in dated cells to come to a final conclusion.

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Hmmm, so in situation 1and 2 posted by L106 the anti c titer eventually drops to undetctable levels, but units selected for transfusion will be negative for c antigen, this is good. IF anti Q is also present in the March sample, maybe is has also dropped to undetectable levels by April (situation 1) or May (situation 2). I say honor it.

I understand what you are saying, but in the hypothetical situations presented, Anti-Q could not be rulled out in the March sample. However, there was no indication to suspect that Anti-Q was present.

Think about the situation where a patient has allo-anti-e. There were probably a dozen or more antibodies that could not be ruled out. However, I doubt that for all future transfusions you made sure that the donor blood was negative for e, C, Jka, Fya, K, Kpa, S, etc., antigens.

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The antibody screen is used a jillion times a day to "rule out" antibody specificities. We usually only require it to have one homozygous cell and sometimes only one heterozygous cell (K). Why do we want 3 hetero or 2 **** once the patient has made one antibody? Having two doesn't make the reactions of weak antibodies any stronger. The only thing having more than one homozygous cell for rule-out does is reduce your odds that one of the cells has a weaker form of the antigen, a poorer fit with the possible antibody or was tested by improper technique (forgot to add sample?). I like to rule out with 2 homozygous Kidd cells in gel because I have seen it show a lot of variability and I would rather not miss a Kidd antibody since they have such a reputation for anamnestic responses and delayed reactions. There are times that I would rather have 2 hetero cells to rule out with for some other specificities rather than only one, but I think routinely finding 3 Kk cells to rule out anti-K is overkill.

On the question of honoring specificities forever because you could not rule them out once: We wouldn't. We don't rule out Cw or Lua or Co b or Di a on our screen cells hardly ever, yet we aren't making sure all units are negative for those antigens. We aren't even antiglobulin crossmatching them. The Co b antigen is almost as common as K and the antibody is considered clinically significant--prabably it is not as immunogenic as K but still not that rare. No harm in E typing the patient because ruling out may be difficult again in the future with an antibody present like anti-M.

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I didn't read everyone's comments so this may be a duplicate. We all say we use homozygous cells for ruling out but we rule out every day using our screening cells. Our screens don't always have homozygous cells for each antigen. We perform electronic crossmatch on negative screens so we could be missing antibodies that show dosage is this a worry for others?

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I didn't read everyone's comments so this may be a duplicate. We all say we use homozygous cells for ruling out but we rule out every day using our screening cells. Our screens don't always have homozygous cells for each antigen. We perform electronic crossmatch on negative screens so we could be missing antibodies that show dosage is this a worry for others?

In the UK, the screening cells are always "homozygous" for those antigens involved in dosage.

I say "homozygous", because, as far as Iknow, the donors used have not actually been tested at a molecular level.

:):):)

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We all say we use homozygous cells for ruling out but we rule out every day using our screening cells. Our screens don't always have homozygous cells for each antigen. We perform electronic crossmatch on negative screens so we could be missing antibodies that show dosage is this a worry for others?

Yes, I think you might want to consider switching to Screening Cells that are guaranteed to be homozygous for the typical antigens that we are most concerned about (Rh, Kidd, Duffy, etc.), or you need to treat your Screening Cells like you treat your Panel Cells (ie: use homozygous cells for rulling out.)

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At a facility I worked at in the past; we would do the inital full-panel work-up for a new antibody; thereafter, we would use a selected cell panel to rule-out, using only 1 homozygous cell (if possible); it became kind of a game "I can rule-out everything with only 3 cells". We also used expired cells; this process was never questioned by the FDA.

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  • 3 weeks later...
Ok, so here's my question: when doing rule-outs, where I work, we have a pile of gel and tube panel cell sets that we use for this purpose, most of which are past their outdates. They still "work", as in, the reactions will still show up, but that's always not made a lot of sense to me--what's the purpose of having an outdate on reagents if they're to be used beyond the expiration? I know you can't always rule out everything on the first shot, with an in-date panel, so what does everyone else here do? I always thought that using outdated reagents was a no-no with CAP, AABB and other regulatory agencies, in any section of the lab? Thoughts?

We do use outdated panels to help w/rule outs. When we Ag type the patient for what we've ID'ed (or can't ID), we also test the outdated cells w/the typing antisera in question.

ie If I was trying to r/o K and found a K homozygous cell on an outdated panel, I would test those cells, along w/my patient, and an appropriate pos and neg screening cell. If my outdated cell still had a strong rxn, I would feel comfortalbe in using it.

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We do use outdated panels to help w/rule outs. When we Ag type the patient for what we've ID'ed (or can't ID), we also test the outdated cells w/the typing antisera in question.

ie If I was trying to r/o K and found a K homozygous cell on an outdated panel, I would test those cells, along w/my patient, and an appropriate pos and neg screening cell. If my outdated cell still had a strong rxn, I would feel comfortalbe in using it.

The only problem with that (much as I admire your thinking; and I do) is that you are not testing like with like.

The grouping reagent you are using on your out-dated red cells is going to be very strong and specific, whereas your sample plasma may well have a very weak, "polyspecific" antibody.

In the example you quote, it might be better to use an old, stored example of anti-K from another patient.

:confused::confused::confused::confused::confused:

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The only problem with that (much as I admire your thinking; and I do) is that you are not testing like with like.

The grouping reagent you are using on your out-dated red cells is going to be very strong and specific, whereas your sample plasma may well have a very weak, "polyspecific" antibody.

In the example you quote, it might be better to use an old, stored example of anti-K from another patient.

:confused::confused::confused::confused::confused:

We are a small hospital and don't freeze old positive samples (often there is nothng left). I'm pretty sure we got the idea of qc'ing old panel cells w/ag typing sera from our former and current BB ref labs. I will check with them next week.

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We are a small hospital and don't freeze old positive samples (often there is nothng left). I'm pretty sure we got the idea of qc'ing old panel cells w/ag typing sera from our former and current BB ref labs. I will check with them next week.

I agree that, if you have nothing else that you can use, grouping reagent is far better than doing nothing at all.

:):):)

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