Our Reference Lab rules out D,f,K,P1, and Xga on a single or heterozygous cell. Also they rule out C and E on one cell in the presence of Anti-D. I am interested in other opinions on this practice.

Thanks.

Our Reference Lab rules out D,f,K,P1, and Xga on a single or heterozygous cell. Also they rule out C and E on one cell in the presence of Anti-D. I am interested in other opinions on this practice.

Thanks.

IT'S DANGEROUS!

:eek::eek:

I believe those were the recommmendations that came out of the 2008 IRL conference (at least the Anti-C, Anti-E in the presence of Anti-D and the exclusion of Anit-K). In fact, based on this conference we have changed our rule out protocols.

More details on your colorful response, please, Malcolm.

I believe their reference is from "Serologic Problem Solving" by AABB.

More details on your colorful response, please, Malcolm.

Well, the thing is Terri, that all individual's red cells have a different number of antigen sites on them.

It is all very well saying that R2R2 red cells have the highest number of D antigen sites for the "normal" Rh types, but an apparent R2R2 from a single source may come from an R2r", who, by coincidence, also has a lower than normal number of D sites on the red cells. It is, therefore, theoretically possible for there to be an anti-D to be present that is weak, and which does not react (visually anyway) with this anti-D. It may be missed.

It may be rare, but it can, but shouldn't happen.

The same applies for all other antigens (although I seriously would not mind missing some of these antibodies (e.g. anti-P1).

Well, the thing is Terri, that all individual's red cells have a different number of antigen sites on them.

It is all very well saying that R2R2 red cells have the highest number of D antigen sites for the "normal" Rh types, but an apparent R2R2 from a single source may come from an R2r", who, by coincidence, also has a lower than normal number of D sites on the red cells. It is, therefore, theoretically possible for there to be an anti-D to be present that is weak, and which does not react (visually anyway) with this anti-D. It may be missed.

It may be rare, but it can, but shouldn't happen.

The same applies for all other antigens (although I seriously would not mind missing some of these antibodies (e.g. anti-P1).

I think we should all request that our suppliers do DNA-based testing on screening cells and panel cells. They would only have to do it once and have it available on a web site. This wouldn't be in place of serologic typing, but in addition. Then we would have information on a larger number of antigens, including Dombrock. And I think that would also give us information on those R2r" cells that we thought were R2R2. (I actually think we had one not long ago - nearly all our passive anti-D's were either reacting stronger with Cell 1 (R1R1) and with Cell 2 (R2R2) or were only reacting with Cell 1. The main reason that I could think of for this to occur was exactly what you suggest.

Anyway, if we all request it, it would certainly carry some weight (I hope).

I think this could be done using BioArray at the Philadelphia Red Cross.

Belva

Please forgive my ignorance, but isn't a R2r cell heterozygous for E and a R2R2 cell homozygous for E. How would they look the same serologically?

thanks

Please forgive my ignorance, but isn't a R2r cell heterozygous for E and a R2R2 cell homozygous for E. How would they look the same serologically?

thanks

Hi harrisonka,

No, what I was saying was that an R2r" (DcE/dcE) cell is serologically identical to an R2R2 (DcE/DcE) cell.

You are absolutely correct in saying that an R2r (DcE/dce) would be heterozygous for the RHE gene and would give positive results with both anti-E and anti-e.

:)

I'm actually surprised a Reference Lab would use this rule-out protocol. When I worked in a reference lab we used three rule outs (homozygous when possible, though K and C & E in the presence of D were notable for the allowed use of heterozygous cells). My current lab requires 2 homozygous cells for rule-out (except for those situations noted above) and another lab I worked in required only one homozygous rule-out.

I think that using only one cell, particularly one heterozygous cell, to rule out any clinically significant antibody is not a sound practice since it increases the likelihood of missing the antibody due to the variations in strength of reactions mentioned in other posts. Of course, that's just what we do when we accept a negative antibody screen, though, isn't it? I'd expect a higher level of performance from a Reference Lab, though.

In the UK, Guidelines state that the screening cells must exhibit apparent homozygous expression of any antigen against which antibodies are known to show "dosage", so that the screening is as reliable as possible (although no screening cells can express all antigens).

Edited October 13, 200915 yr by Malcolm Needs
rotten syntax (probably not much better now either!)

Note: Due to the issues with Anti-E strength using Ortho MTS Gel technology, we only r/o E with homozygous ONLY...which means in the presence of Anti-D we rarely have a cell available that can r/o E.

So what happens if you have an anti-E that truly responds to homozygous dosage only...in other words, no matter how many heterozygous cells you run, they will all be negative? I'm not sure it matters whether you run one or three heterozygous cells if the antibody is reacting with homozygous cells only. If you decide to rule out on homozygous only, then you will never (OK, very rarely) be able to rule out anti-C or anti-E in the presence of anti-D (unless you are able to do it by phenotyping the patient). Do you then always give E and C negative units to all patients with anti-D?

So what happens if you have an anti-E that truly responds to homozygous dosage only...in other words, no matter how many heterozygous cells you run, they will all be negative? I'm not sure it matters whether you run one or three heterozygous cells if the antibody is reacting with homozygous cells only. If you decide to rule out on homozygous only, then you will never (OK, very rarely) be able to rule out anti-C or anti-E in the presence of anti-D (unless you are able to do it by phenotyping the patient). Do you then always give E and C negative units to all patients with anti-D?

If you really can't rule out anti-E or anti-C because you haven't an r"r" or r'r' cell available, then giving rr is the only alternative, but how many people really use these cells each time? Indeed, how many have them available ever. Not many I would venture to say.

We do (frozen) because we are a Reference Laboratory, but no way would I sanction my staff to thaw these each time we had an apparent anti-D that may or may not also have an anti-E or anti-C that only reacts with a "double dose" of the antigen.

:(

This is only really a problem when anti-D is present. We DO r/o C with 3 heterozygous. But having had a large number of patients with anti-E showing dosage, our medical director decided we shouldn't rule out E with heterozygous cells. It's not a big deal to give E-negative units to patients with Anti-D, as most Rh negative units are also E-neg. It's just a minor inconvenience to have to phenotype the unit for E.

Addendum: remember...I'm talking about MTS GEL methods...the manufacturer has acknowledged problems with E detection in the past.