At one time, anti-D was the most common antibody implicated in severe HDFN. Due to the routine administration of Rh immune globulin (RhIG) to Rh negative mothers, the incidence of anti-D HDFN has decreased substantially. The antibody has not been eliminated, however, and it is still implicated in HDFN and can be associated with severe disease,but Anti-K will be the most common from now on.

The development of alloantibody such as anti-K to fetal RBC exposure may be less if the fetal cells are ABO incompatible with the mother. This is proposed to be due to the shortened life span of ABO incompatible fetal red cells in maternal circulation.Anti-K is frequently associated with a severe form of HDFN due to the ability of the antibody to suppress fetal erythropoiesis in addition to causing hemolysis. Some antigens are well developed on fetal cells (e.g., Kell), some are slightly weaker (e.g., ABO), and some are poorly developed or not present at all on fetal cells (e.g., Lewis).

Edited January 13, 201213 yr by Abdulhameed Al-Attas

This is a critical titre and hydrops fetalis is considered to be likely,In general, critical titers of anti-D are 16 or 32. Titers for anti-K are generally lower, a titer of 8 being typical. Titers are generally performed every 4 to 6 weeks. Once the titer reaches the predetermined critical level, additional testing such as ultrasound, amniocentesis, or cordocentesis are generally indicated to determine the severity of the disease.

It was only last week that I sent a sample from the hospital I work in, to Malcolm’s RCI laboratory on a lady who is 16 weeks pregnant with an anti-K. Malcolm’s laboratory has reported back an anti-K titre of 16000 with a request for repeat samples at 20 weeks, samples from the partner and advice to refer the lady to a specialist fetal/maternal unit. If I remember correctly (telephone report so far) the samples will be sent to the International Blood Group Reference laboratory in Bristol

I suspect we will have little to do with the further management of this patient, because I am sure she will be referred and rightly so.

Steve

:)

Edited January 13, 201213 yr by Abdulhameed Al-Attas

We do not type our OB patients for K, nor do we transfuse K negative units to them. I have not heard of any cases of HDN caused by anti-K at our hospital.

In Oklahoma, anti-K has not been that frequently encountered with severe HDN. In fact, we have seen in some cases the titer of the antibody rise to 1:32/64 levels and the baby turns out to be Kell negative. I think the comments made concerning the relatively low frequency of K+ in the population (at least in OKLA). It will be interesting to follow the work done with the HLA alleles and the association with HDN. I also wonder if the blood transfusion triggers are different for different regions. Sometime UV lights work well.....

. It would ask a lot of them to keep anti-K for the occasional young woman being transfused and then if the only 2 O units they had happened to be K+ they would be scrambling. They are all generalists that would have to remember these special rules twice a year.

As 85% of the Caucasian population is K neg it isn't at all a big ask. Randomly selecting a bag from the fridge would only have a 15% chance of it being K+ which is why incidence is low. Yes incidence is low but the consequence for the 15% of those 15% who have a K+ baby is severe.

And you really should credit you staff more intelligence. I find your statements about generalists quite insulting!

I have great respect for generalists! They have to know every area of the lab and yet might deal with a certain problem only once ever year or two. I certainly meant no disrespect and I am sorry that you feel insulted.

Hi there

I am hoping someone with knowledge could interpret some lab results please.

I am currently 15 weeks pregnant and my bloodwork came back at 11 weeks as group B Negative (which I already knew) and Antigen K- with a titre of 1:64 which I understand to be critical level for an anti-Kell pregnancy. They believe I got the antibodies from a transfusion in 2003 (previous pregnancy though diferent partner).

Anyway my husband's results are back and no one here seems to understand them as it seems to be so rare we I live. His group is A negative so although my healthcare team didnt tell me I believe this means I dont need to get the anti-D shots this time round. However his K results came back as K-k+

Can someone tell me is this means our baby is at high risk or does the fact its K- for my husband mean the baby will definitely be negative? I understand the little k+ may relate to cellano but am unsure what these results mean in our case (and how much to worry! moreso because no one has come across this)

Many thanks in advance

It is NOT written well,But you can sleep easy.

Hi there

I am hoping someone with knowledge could interpret some lab results please.

I am currently 15 weeks pregnant and my bloodwork came back at 11 weeks as group B Negative (which I already knew) and Antigen K- with a titre of 1:64 which I understand to be critical level for an anti-Kell pregnancy. They believe I got the antibodies from a transfusion in 2003 (previous pregnancy though diferent partner).

Anyway my husband's results are back and no one here seems to understand them as it seems to be so rare we I live. His group is A negative so although my healthcare team didnt tell me I believe this means I dont need to get the anti-D shots this time round. However his K results came back as K-k+

Can someone tell me is this means our baby is at high risk or does the fact its K- for my husband mean the baby will definitely be negative? I understand the little k+ may relate to cellano but am unsure what these results mean in our case (and how much to worry! moreso because no one has come across this)

Many thanks in advance

Hi angelstar,

Yes, it means that you can rest easy.

You have a pair of chromosomes that carry the genes that encode for the Kell antigens (a pair of chromosome 7), and you will pass on one of these chromosomes to your unborn baby. Your husband will, of course, also have a pair of chromosomes that carry the genes that encode for the Kell antigens (again, a pair of chromosome 7), and he will also pass on one of these chromosomes to your unborn baby.

If you have anti-K, it means that you must be K negative, which means that you are K-k+ (or that you have two k genes).

Your husband is also K-k+, which also means that he has two k genes.

Each of you will pass on one of these k genes to your baby, which means that your baby will also be K-k+ when he or she pops into the world, and so he or she will NOT be affected in any way by your anti-K.

Incidentally, I'm not sure who told you that the K-k+ type is rare, but, actually, in ALL populations throughout the world, it is the most common Kell type and is actually very common indeed.

I hope that I have been able to calm any doubts that you have had.

Malcolm is perfectly right, not that he needs my acknowledgement.

To add: Cellano is the name of little k. The majority of people acroos all ethnicities have the k (cellano) antigen and not the big K antigen.

Indeed you are as safe as can be, given the lab results that you posted, and the situation regarding danger to the baby is as if you did not have the anti-K.

Related to the topic and revealing my ignorance: regarding serving fertile women with K negative blood, do you mean the Kell status of RBCs only, or platelets as well? There are bound to be a few K antigens in there no matter how the platelets were collected, if they're from a K positive donor, I think. Are platelets from a K positive donor sufficient to cause antibody formation? Is there a safe dose? Or a least known immunising dose?

We do it only for red cells.

I must confess that I have never heard of K+ platelets causing immunisation (the K antigen isn't on platelets, but, as you say, there are almost bound to be some K+ red cells floating around), but, just because I haven't heard of it, doesn't mean it hasn't happened.

Thank you, Malcolm. Neither was the OB/gyn specialist now working at our serology lab aware of any K immunisations by platelets only. Also, she knew of no recommendations or policies which would limit fertile women to K negative platelets.

 

We've been handing out K negative reds for girls and fertile women for quite a while now, but haven't limited platelets. Like you said, not knowing doesn't mean it hasn't happened, but at least we're in good company in not knowing.

If we give anti-D to cover allo immunisation when giving Rh- patients Rh+ platelets, surely we should be giving them K- platelets?

I've never had a pregnant woman needing platelets before but if I did I would order them... hmm that's a point - do UK platelets say the K-type? Will check next time a bag comes in

• I think whether give K neg platelet to fertile K neg women depends on the lest amount K pos red cells to stimulate anti-K antibodies.