NK Assay (Killing Percentage)

darlenesommerville

13 Posts
Reply NK Assay (Killing Percentage) Posted on: Oct 24, 2011 at 3:08am
Confused. Hoping you can help.

Some reproductive docs say a 50:1 of < 15% is normal, while others say < 10% is normal. I've posted questions to some other docs as to why this is, and the only response I'm getting is that "different drs have different cut-offs." That's quite obvious. My question is...why? Are these percentages arbitrary? Or are there studies behind them?

The reason I'm asking is because on another patient infertility support board, many of the women have killing percentages somewhere between 10 and 15 %. It is very confusing because some of the women say these are normal and some say they are abnormal, depending on who their doctor is. You can see how frustrating this is - especially for the girls who have had multiple failures! Because of the lack of consistency, some of the girls with multiple losses are thinking maybe their killing percentages of 12.4% or 11.8% (for example) are actually elevated, even though their docs are saying otherwise.

Can you help???

Dr. Braverman

2004 Posts
Re: NK Assay (Killing Percentage) Posted on: Oct 25, 2011 at 1:00am
ok here are the answers look no further .

1. different labs have different results , I have sent the same specimen to different labs several times to test this theory and I have found that RIA in California is generally 5 points lower than RF lab in Chicago hence the different cuttoffs. This is most likely due to different techniques and the most obvious answer that you have been looking for.

2. I dont agree with either one, as the literature is sparse and vague on this, NKa alone is not of much value as you need to look for evidence of the "chain" reaction with immune rejection of an embryo , and too many times its only the NKa that is elevated and all other findings are normal. Studies have shown in this situation it may not even be immune at all. Especially in the "borderline" results of 15-20(using RF levels).

3. Many things other than immune rejection can artificially elevate NKa such as the needle going in the arm , stress, a recent infection and just the fact that the NKa varies wildly each time it is drawn on the same patient. this is why you must look for other signs of immune activation to go along with the NKa i.e. the "chain reaction" this is why we use a wieghted index score(good literature on this) to add up all the abnormalities and when they reach a certain limit we begin to suspect and treat immune issues.

I hope that helps.
Dr. Jeffrey Braverman MD FACOG
Medical Director
Braverman Reproductive Immunology P.C.

darlenesommerville

13 Posts
Reply Re: NK Assay (Killing Percentage) Posted on: Oct 25, 2011 at 1:11am
This does help! Thank you so much for such a detailed response! So far you're the only doc who has taken the time to "think" about the question and respond with an answer that makes sense. Thank you again!

So here's a question for you - I did have my NKa tested at RIA and received a 50:1 of 10.8%. I was also tested for other immune issues such as APA which came back normal. My doc told me my "raised" NKa was due to my husband & I having a partial DQa match. That was the only thing that popped as abnormal.

So, in your "expert" opinion, knowing that I was tested at RIA and that I have a partial DQa match, do you think 10.8% is elevated???

I was put on Intralipids (100ml) for my 3 failed cycles...

Dr. Braverman

2004 Posts
Re: NK Assay (Killing Percentage) Posted on: Oct 25, 2011 at 1:10pm
okay heres the answer to both questions

I dont think 10.8 is significant(especially when its the only parameter measured) and a partial DQalpha match is of NO significance. So at this point you need quite a bit more information before any treatments are offered. Such as a complete HLA assessment, and a "FULL" immune profile .

I would be happy to help you if you would like.
Dr. Jeffrey Braverman MD FACOG
Medical Director
Braverman Reproductive Immunology P.C.

darlenesommerville

13 Posts
Reply Re: NK Assay (Killing Percentage) Posted on: Oct 25, 2011 at 3:49pm
Thanks again Dr B! I did have full HLA testing and everything else was fine. Only the DQa came up as a partial match. I do however need a full immune workup since I was only tested for APA & ACA (normal), and of course NKa (slightly elevated according to RIA).

One more question regarding your response above that partial DQa match is of no significance...

My previous doc told us that 1 in 2 embryos from my husband & I will be "matching" due to our patial DQa issue, and that with each matching embryo I will most likely have a failed cycle because my body will reject the matching embryo (due to it being too similar to my uterus). Apparently my elevated NKa is my body's reaction to matching embryos after the birth of our son years ago. I know there are lots of docs in the field who do not believe this. Where do you stand on this Dr B?

Thanks again!!!

Dr. Braverman

2004 Posts
Re: NK Assay (Killing Percentage) Posted on: Oct 26, 2011 at 1:56am
I respectfully but completely disagree with what you were told about the DQalpha you should move on from that theory its not correct and the literature has completely disproven that (as well as my own extensive experience with it).
I would like to see the full HLA screen on you. And as you said you still need a full immune workup. I would be happy to assist you with this.
Dr. Jeffrey Braverman MD FACOG
Medical Director
Braverman Reproductive Immunology P.C.