Rule outs for Anti-Kell

[donellda]

We have been having a discussion on rule out cells for Anti-Kell. I always use cells of a homozygous expression for rule outs with a few exceptions. In the case of Anti-D, I will use heterozygous cells to rule Anti-C and Anti-E. In the past for rule outs for Anti-Kell, we were told that 2 cells of a heterozygous expression for Kell was acceptable in the absence of a homozygous cell. In the past few years, we have been using one heterozygous cell to rule out Kell. We were questioned by another hospital on our use of the one heterozygous cell. They stated that they use 3 heterozygous cells in the absence of a homozygous cell. I contacted our local reference lab to see what they do, and they said that, while 2 cells of a heterozygous expression would be better, they only use one for rule outs. I am just wondering what everyone else does in this instance.

[AMcCord]

I suppose your comfort level would depend on the method you use. If you are a gel user who has missed an anti-K, you might be more inclined to use more ruleouts. I feel pretty secure with only one if I'm using PeG.

[rrcc1974]

We are gel users. For Anti-Kell we use 2 heterozygous cells or 1 homozygous cell.

[Dawn]

We require 3 to rule-out, we would prefer that one of them is homozygous, however with anti-K we allow 3 heterozygous.

[rcurrie]

In SBB school we were given 10 lashes with a transfusion set for saying "Anti-Kell". Kell is a system, not an antigen.

That said, there just aren't that many K+k- cells floating around on the average panels (or screen sets, for that matter). Whenever I have had an unidentifiable antibody (that is, everything ruled out on the panel), I suspected anti-E or anti-K, and went from there by unruling out E+e+ and K+k+ cells to see if either antibody was still possible. Usually, it was one or the other in the final outcome.

BC

[Lcsmrz]

I think there should be a difference between a Reference Lab and the rural 100-bed hospital: one stocks multiple panels, while the latter is lucky to stock one. One panel will have modified rules to decide when to call an ID and when send it out.

Our little hospital with one panel uses one homozygous or two heterozygous cells (apologies to Dr Judd) to rule-out antibodies, with the exceptions of Anti-C and -E in the presence of Anti-D.

[Eagle Eye]

we use atleast 2 heterozygous. we use gel. If we have one heterozygous on screening cell and one on panel we rule out anti-K. With gel panel(A), it is difficult to find homozygous cells.

[Philip Thornton]

We use one homozygous or in the absence of one at least two heterozygous for K rule outs.

[adiescast]

Thanks, Bob, for reminding us of our antigen systems! We prefer to use a homozygous cell for rule out, but often there is not one. We allow rule out on a single heterozygous cell in the absence of suspicious activity. My theory is (and it generally holds up for the Kell system, not so much with MNSs) that if the antibody won't react with one heterozygous cell, it won't react with the next one either, so either you require the homozygous rule out or you take the risk. We do not use gel and have not thus far had a problem with anti-K1 not reacting with heterozygous cells.

I try not to be too paranoid!

[skopti]

We use 1 homozygous cell, if not available, then we use 2 heterozygous cells.

[Mabel Adams]

Although we allow 2 single-dose K cells, we must not fall into the belief that this is actaully more sensitive than one single-dose cell. Due to dosage, a double-dose cell may be more sentitive. But using 2 single-dose cells reduces the likelihood that an anti-K will be missed because one of the K+ cells did not react due to technical or other difficulties. Statistically, anti-K is a very common antibody so it is worth some extra effort to make sure it is not there.

[ckcheng]

Anti-K does not show dosage and k is a high incidence antigen. It is very difficult for one to select K+k- cell to exclude anti-K. Especially if your practice is to choose only panel cells that are not expired. One heterzygous cell can be used to exclude anti-K.

CK Cheng, MSc, SBB(ASCP), CQA(ASQ)

HONG KONG

July 23, 2008

[Liz0316]

If an antibody such as anti K is dosing and not reacting on heterozygous cells, what is the difference if you run 2,3 or 10. It's not reacting on heterozygous cells.

We allow rule outs for anti K on a single cell, because K does not normally dose. Now if you need to run selected cells, you will more than likely run another K+ cell, whether it be heter or homozygous, so you'll feel better, but truthfully, that's all it does.

[NedB]

The AABB Technical Manual has a discussion about probabilities for ruling in or out. We follow their suggestion; three cells to rule in or three to rule out to have a 95% confidence level; with the caveat that one homozygou equals two heterozygous. The AABB protocol is basically sound for high- and moderate- incidence antigens, but does not give a mathematically sound 95% confidence level with low-incidence antigens. That said, antibody identifications sould be correlated to the percentage of incompatible AHG crossmatches with supposedly antigen -negative units. If the percentage is high, guess what - you missed something. Incidentally, we use (and love) gel.

[SANDRA CORBETT]

We Use 2 Heterozygous Cells For Ruling Out Kell, Unless We Are Lucky Enough To Get A Panel In With A Homozygous Kell. Sandy Corbett

Jordan Hospital Plymouth, Mass

[NedB]

I mentioned the AABB discussion about probabilities. The reason for the use of probabilities is that most antigens show some diversity (Anti-D in Rh Pos patients). By selecting more than one cell to rule out you reduce the odds of missing an antibody which was stimulated by a single donor with an uncommon or less than common form of the antigen.

[debbylb]

We rule everything out with either one homozygous cell or two heterozygous cells.

[csjuarez]

We routinely rule out the "common" red cell antibody specificities with 2 homozygous cells. However, the case of the K1 antigen is one of the exceptions to the rule and is commonly ruled out with 2 heterozygous cells. Other exceptions are C and E in the presence of anti-D (2 heterozygous cells), S in the presence of anti-M (1 homozygous and 2 heterozygous cells if 2 homozygous are not available on the indate panels), and the "cold" antibodies Lewis, M, N where we use only 1 homozygous rule out.

Though I've worked in labs where a single homozygous rule out was the norm, I'm not comfortable with that. As has been mentioned, it is very possible to miss something significant when only one cell is used for a rule-out.

We are also gel users and I don't fear we are missing significant K, E, or other specificities due to the method. Any system will miss weak reactions from time to time -- none is perfect, but we are pleased with our experience with gel.