So, I was reviewing completed antibody panels and discovered that some techs are having trouble  ruling out Kell.

I was taught that Kell had the potential to show dosage but often did not. So, to be safe,  you wouldn't rule Kell out on a heterozygous cell. Personally, I always try to use cell 22 on Panel B from Ortho. It's homozygous. I can lay my head down at night. However, the newer techs are being taught ( or at least the ones I seem to work with) that Kell doesn't show dosage and can be ruled out on 1 heterozygous cell.

I called our local Blood Bank Reference lab. They try to rule out Kell on the homozygous cell as long as anti-E and anti-D are not a factor, but if they cannot, they use 2 or 3 heterozygous cells.

So, my question is: How can I instruct my BB techs to do this? What's really right? I'll take whatever you got! Thanks in advance!

If that's the way you want it done, write it into a procedure.  40 yrs ago I learned that Kell did not exhibit dosage and could be ruled out with a heterozygous cell.  My experience has taught me otherwise.  Still, I try to r/o w a homozygous cell but it does not bother me to r/o using a heterozygous one. 

I am OK with ruling out the presence of anti K with single dose cells. I think I have seen anti K showing dosage only 1x in all m years of BB. 

It should be based on what is written in your SOP. For me, big K can be rule out using one heterozygous.  It does not show dosage. 

I am going to make myself VERY unpopular here.

Firstly, there is no such antigen as Kell (the closest is K5 or Peltz), and there is no such antibody as anti-Kell (the closest is anti-K5 or Anti-Peltz).  The blood group system is Kell Blood Group System, but the first antigen within that system is K, and the antibody directed against that antigen is anti-K.  The ONLY individuals who can be described as being Kell Negative are those incredibly rare individuals who have the K_o phenotype.

Secondly, ONLY genes can be either homozygous or heterozygous (or, in some cases, hemizygous).  Antigens CANNOT be described as either homozygous or heterozygous (or, in some cases, hemizygous).  As red cells do not contain a nucleus, but merely express antigens, as the result of the individual inheriting certain genes, red cells CANNOT be either homozygous or heterozygous (or, in certain circumstances, hemizygous).  The correct way of describing such red cells is to describe them as having either homozygous expression, or heterozygous expression (or, in some cases, hemizygous expression).

Having got that off my chest (BUT, IT IS VERY IMPORTANT), I will now address the underlying question of this thread.

Without doubt, the reaction between an anti-K and the K antigen CAN show "dosage"; I don't think anyone would dispute that these days.  However, the more important question is, over the years and years and years that we have been using antibody screening cells that are K+k+, and have, therefore, NOT detected an anti-K that only reacts with red cells that have (supposed) homozygous expression, and do not forget, some of those cells may actually have come about as the result of a genotype of KE02/KEN, which means that the red cells actually have hemizygous (or "single dose"expression), how many patients have actually suffered a haemolytic transfusion reaction that has been clinically significant, causing morbidity or mortality?  I would contend that, having looked through as much of the available literature as I have been able, the answer is zero.

Obviously, if there is an anti-K present in the first place, albeit, it is undetectable by routine serological techniques, then transfusing the individual with either K+k+ or K+k- red cells will boost the anti-K, but it has not, as far as I know, resulted in mortality or morbidity, but will, almost certainly, result in an increase in titre and avidity of the antibody (I recognise, of course, that this could have disastrous results in a pregnancy, but only if the pregnancy is not properly monitored).

On top of all the above, it is well-known that there are mutations of the KEL1 gene, resulting in "unusual" amino acid substitutions, resulting in weakened expression of the K antigen, are not unknown.

It is well known that almost all blood group systems have their "quirks", which means that nobody can rely 100% on their antibody screening cells, BUT WE ALL DO!

I would politely suggest that an anti-K that is only detectable with red cells that are (genuinely) K+k- are not that important.

I have actually seen a number of these beasts - usually as a result of a complaint that cell x did not pick the cell up when cell y did - and cell y just happened to be a K+k-.  Usually these were antibodies that were detected years ago and whose levels have now fallen, predictably, with time.

The pragmatic point is - you are never going to get every single set of screening cells with a k- cell in them.  If you've got one, great - use it!  If you haven't I still would not lose any sleep over it.  Malcolm's points above are of course totally relevant as usual

I've seen one patient showing dosage for anti-K. That said, we still rule out with 2 cells. If we can find a K⁺k^-  cell, we use it. If we can only find K⁺k⁺ cells, we use them and don't use any sleep - as Malcolm pointed out, that's what you get on the antibody screen.

Assuming that most patient samples are tested against screening cells that do not have a K+k- cell,  is the exclusion of anti-K1 using a screening cell with heterozygous expression allowable if the antibody screen result is negative but not allowable if the antibody screen result is positive?  

If the facility endorses a computer "crossmatch" with a negative antibody screen (using a K+k+ cell) do you require additional testing with a K+k- cell to exclude anti-K1?  Ours does not - but we also allow exclusion of anti-K1 with a K+k+ cell for any patient.

Just a side note, my wife's anti-K would show up at immediate spin, go away at 37oC  and then come back strong at AHG.  Her anti-D was detectable only at AHG.  Her anti-S disappeared completely after about 1 year.  She's a nurse, you can't expect her antibodies to be normal!!