Is there consensus that anti-K cannot be excluded if a single K+k- panel cell is agglutinated regardless of the number of K+k+ panel cells that are unagglutinated?

Using ORTHO Resolve Panel A for a patient with weak anti-D (reacting 2+), anti-K is excluded on the basis of a single non-reactive K+k+ panel cell. If you add Resolve Panel B, anti-K is/is not excluded based on 1 panel cell that is D+, K+k- and 2 non-reactive panel cells that are D-, K+k+?

With these findings, would your current policy require transfusion with K-negative red blood cells?

We allow rule out of K with a single dose cell--preferably more than one such cell--although 2 cells doesn't make the antigen stronger, just reduces the likelihood of errors and missed reactions due to weak antigen expression. One factor that I consider is, how likely is it that if I missed a weak antibody I would give an incompatible unit? That is much less likely with K than with c. Also, K antibodies just tend to be sturdy and detectable-especially in modern testing methods. Remember, you are ruling out every day with whatever zygosity of cell is on your Ab screening cells (for all of your patients with negative screens). Most screening cell sets don't include a double-dose K.

I agree with you entirely Mabel.

Just occasionally, as a Reference Laboratory, we will detect an anti-K that is only reacting with multiple examples of K+k- red cells, but not with multiple examples of K+k+ red cells, and we do honour these, but quite how clinically significant these antibodies are is debatable.

In the case of Dansket I would not select K neg blood, because there is hint thet there is an anti K present (you can blame your reaction on the anti D). In a case where only the K+k- neg is reactive (and 2 or more K+k+ are non rective), I would look further for the anti K or select K neg blood. A few weeks ago we had a case like that, screening neg and crosmatch positive (was KK).

Peter

We get 16 and 20 cell panels from Immucor, 3%. Convert to 0.8%, run another heterozygous Kell cell and call it a day.

I would call it anti-K because if your patient is types as K neg it's not going to hurt to give K neg blood and most units are K neg. Have you tried running ficin to see if the hetero cells pop out?

Based on our protocol, which is the common 3 and 3 r/in r/out rule, if we had three neg calls for a K it is considered ruled out (dosage not a big deal normally with Kells.) And has been pointed out, the one reactive cell in this case was probably due to the D.

But even if that K+k- cell was negative for D, I would think the reaction more an equivocal one than due to the K that happened to be on it. Still, if that were the case, we would have looked for another K+k- cell in another panel just for peace of mind.

Scott

I'm finding it strange that they would even run the whole Resolve B panel when they suspected anti-D from screen/Resolve A, but that's me...

I'm finding it strange that they would even run the whole Resolve B panel when they suspected anti-D from screen/Resolve A, but that's me...

I agree with you. However, this scenario was intended as an example to pose the question, "Whenever you have a reason to run Resolve Panel B and the K+k- panel cell is agglutinated, can you exclude anti-K if there are one or more K+k+ cells that are not agglutinated?"

Using the logic that you can't rule out K in this case would mean that you pretty much can't rule out anything without a non-reactive homozygous cell for that antigen. Let's say you have multiple antibodies, anti-c and anti-Fya, so most cells react. If you had 2 Ss cells that did not react, you could not rule out S because the anti-c or Fya reacted with a cell that happened to be SS. When I am dealing with most cells reacting, I am willing to rule out using heterozygous cells as long as there is nothing in the reactivity that suggests there is another weak antibody lurking--like the D (R1R1) & KK cell is reacting stronger than the other R1R1 cells tested. I think this also may depend on your resources. Reference labs have many more panel cells to choose from.

Oh I see. I missed the part that the K+k- cell is also D+. Sorry!

I would say good luck finding multiple k- cells to prove your point. And yes, it would have to also be D negative to get a true rule out. Good luck there too. We would rule out based on the hetero, plus your full crossmatch will catch any odd thing that also happens to be on that homozygous K cell, that might not necessarily be K..... Darn things don't read the books do they?

Well - there again I think you need to think about how sensitive the test method is that you are using. Some labs, for instance ARC IRLs, routinely rule out aby on heterzygous cells when testing in PEG, enzymes, GEL or Solid Phase.

In the NHSBT in the UK, we never do, unless there is no alternative. For example, we had a patient with anti-K+Era (a nasty little combination!) where we could only rule out the presence of an anti-S with an S+s+ K-, Er(a-) red cell.

If we have to rule out using cells with presumed heterozygous expression of an antigen, we say so on our reports, and leave it up to the hospital as to whether they want to honour (in that case) the possible anti-S and give S-, K- blood.

I see your point Malcolm, but I think that when a sample is sent to a reverence lab, the reverence lab has to give the advise. In that situation we diside we can not rule out and say select S negative.

The presence of multiple antibodies (or HFA) can never be the reason to rule out on heterozygous cells. You have to search for other cells or use other methodes to rule out, for example absorption.

Last year we had a pregnant women with anti P+Pk+P1, and the father is K+ and E+. We do not have cells that are P- and E+ or K+. So have ruled out these antibodies several times during pregnancy with absorption. And the good news is she is now pregnant again!!

Peter

Under normal circumstances Peter, I completely agree with you.

It was just that, in the case of our patient with anti-K+Era, he was for urgent surgery, and we didn't have time to perform adsorption studies - it took long enough to identify the anti-Era!!!!!!!!!

I'm glad that lady is in your "patch", and not mine!!!!!!!!!!!

Do screening cells in the UK always contain a k- cell? If not, you are ruling out anti-K on all patients with a negative screen using a heterozygous K+ cell. Or is K not one of the ones for which double-dose is required for rule-out?

Hi Mabel,

No they don't usually have a K+k- screening cell, and we do rule out anti-K using heterozygous expression with these.

Anti-K, without doubt, can, occasionally, show dosage, but it is very rare, and I am comfortable with this.

Just to argue against myself, however, we had a patient in just this week who had an anti-D+C+E, but gave a sinle 1+ reaction with the K+k- panel cell after it had been treated with papain (nothing by straightforward IAT, but 1+ by enzyme-IAT). I asked my staff to test the patient against two other examples of rr, K+k- red cells, and loh and behold (or, as we were usung papain-treated red cells, perhaps that should be "Low" and behold), there was the weakest anti-K that I think I have ever seen in 40 odd years in the game - so it can happen.

Malcolm, just a side note. My wife's anti-K shows up at immediate spin, goes away at 37 and then comes back at AHG (PEG and LISS testing). She's a nurse and they seldom do things the way normal people do!

If this unusual patient had not also had another antibody, you would not have found the weak anti-K. I know we never want to ignore one that we know about, but would the patient really be harmed if they lost the transfusion lottery and got one of the 9% of units that are K+? Or at least more harmed than are patients with antibodies to low freq antigens that we don't detect and happen to transfuse--a scenario we have obviously accepted since we do IS or electronic xm.

I doubt it very much Mabel.

If it doesn't react by IAT, but does by enzyme-IAT, we tend to consider it clinically insignificant (although we are honouring it); the exception being anti-Jka.