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What are your rules for ruling out?

What are your rules for ruling out?  

168 members have voted

  1. 1. What are your rules for ruling out?

    • 1 homozygous
      75
    • 1 homozygous and 1 heterozygous
      9
    • 2 homozygous
      52
    • 1 heterozygous
      4


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A minimum of 2 cell samples expressing presumed homozygosity of the gene, if available.

In some cases, of course, this is not possible (for example, we had to group the partner of an Oh pregnant lady the other day. He was H+, but was he HH or Hh? Who knows?).

There are also rare occasions when we only have one example of a particularly rare "homozygous" type (such as a Cw+, Cx-, MAR-), but there is nothing else you can do under the circumstances.

:)

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From the UK BCSH guidelines (these can be found in the reference section of BBT- Library/ UK/ compatibility guidelines):

7.7.2 The specificity of the antibody should only be assigned when it is reactive with at least two examples of reagent red cells carrying the antigen and nonreactive with at least two examples of reagent red cells lacking the antigen. Note that,wherever possible, the presence of anti-Jka, anti-Jkb, anti-S, anti-s, anti-Fya and anti-Fyb should be excluded using red cells having homozygous expressions of the relevant antigen.

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We use one homozygous or if absolutely necessary two heterozygous to rule out. Then 3 positives and 3 negatives reacting as expected to rule in.

Of course you always have to look at the whole picture and use your brainpower to see if you can figure anything out when things are not clear cut. Which seems to be happening more and more often these days!

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We use one homozygous or if absolutely necessary two heterozygous to rule out. Then 3 positives and 3 negatives reacting as expected to rule in.

Of course you always have to look at the whole picture and use your brainpower to see if you can figure anything out when things are not clear cut. Which seems to be happening more and more often these days!

Brain power? Bang goes any chance that I could do it then!!!!!!!!!!

:o:o:o

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Um...

My lab strictly uses 3 homos... and 2 heteros can replace one **** if absolutely necessary...

What's your take on my lab's methods? =S

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eric 1980 - I'm not saying anything is "wrong" with your lab's method of using 3 homozygous positive cells to rule out an antibody, but I have a question. Using this method must frequently leave quite a few antibodies that you cannot rule out. What do you do with that information? Do you report out the list of antibodies that were left in the "cannot rule out" list?

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eric 1980 - I'm not saying anything is "wrong" with your lab's method of using 3 homozygous positive cells to rule out an antibody, but I have a question. Using this method must frequently leave quite a few antibodies that you cannot rule out. What do you do with that information? Do you report out the list of antibodies that were left in the "cannot rule out" list?

I must agree with L106 that this system must "hold you to ransom" on occasions. It may be okay if you have a plasma containing one or two antibodies, but when you have an plasma containing three or four (or more) alloantibodies (even if they are of a "common" specificity), it must give you a headache as to how to find the necessary red cells.

How do you cope with, for example, a sickle cell patient with an anti-U, an anti-Fy3 or an anti-Jsb? How would you find three examples of U-, K+k- or Fy:-3, K+k- cells, or, come to that three examples of Js(a+b-), Jk(a-b+) red cells (or would you alloadsorb in such circumstances)?

:confused::confused:

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L106: According to my lab's policy, if we cannot achieve 3 homozygous antigen cells, we got to go back to prepare expired (less than 3 months) reagent panel cells in order to achieve it. If we are still unable to achieve 3 homozygous antigen cells, we will send it out to our reference lab for ABID...

Malcom: I ever had a patient with anti-Fya and anti-Fyb. The lab will just send the specimen to the reference lab for ABID... This also applies to all your examples in your post...

My lab do not do ABID routinely, and my colleagues are also not trained to do it. Which is why in the other thread, I said that I really gained tonnes of insight and possibilities ever since I participated in this forum....

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L106: According to my lab's policy, if we cannot achieve 3 homozygous antigen cells, we got to go back to prepare expired (less than 3 months) reagent panel cells in order to achieve it. If we are still unable to achieve 3 homozygous antigen cells, we will send it out to our reference lab for ABID...

Malcom: I ever had a patient with anti-Fya and anti-Fyb. The lab will just send the specimen to the reference lab for ABID... This also applies to all your examples in your post...

My lab do not do ABID routinely, and my colleagues are also not trained to do it. Which is why in the other thread, I said that I really gained tonnes of insight and possibilities ever since I participated in this forum....

Ah right. Now I understand where you are coming from.

Sorry about the misunderstanding.

:redface:

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In my lab we follow the ANZSBT guidelines as shown below

http://www.anzsbt.org.au/publications/documents/PLP_Guidelines_Mar07.pdf

2.1.3.5 The specificity of an antibody [including each individual antibody in multiple antibody mixtures]

can normally be assigned when it is reactive with at least two reagent red cells carrying the

corresponding antigen and non-reactive with two reagent red cells lacking the antigen.

2.1.3.6 The presence of anti-Jka, anti-Jkb, anti-S, anti-s, anti-Fya and anti-Fyb should be excluded using

red cells with double-dose expression of the corresponding antigens.

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In my lab we follow the ANZSBT guidelines as shown below

http://www.anzsbt.org.au/publications/documents/PLP_Guidelines_Mar07.pdf

2.1.3.5 The specificity of an antibody [including each individual antibody in multiple antibody mixtures]

can normally be assigned when it is reactive with at least two reagent red cells carrying the

corresponding antigen and non-reactive with two reagent red cells lacking the antigen.

2.1.3.6 The presence of anti-Jka, anti-Jkb, anti-S, anti-s, anti-Fya and anti-Fyb should be excluded using

red cells with double-dose expression of the corresponding antigens.

This is, essentially, the same as the Guidelines in the UK.

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Ah right. Now I understand where you are coming from.

Sorry about the misunderstanding.

:redface:

No issues! ^_^ I'm also learning how hte othe BTS do this. ; )

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One thing that I have not understood throughout this thread is, in the case of antibodies/antigens that show dosage, and I know that the number of antigens for a particular specificity varies with the human source of the red cells, if the antibody/antigen reaction is showing dosage, surely it doesn't matter how many examples of red cells expressing "heterozygosity" are used, they are still going to have negative reactions.

Surely, cells expressing "homozygosity" is the way to go, if they are available?

:confused::confused::confused:

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I agree with you Malcolm. We do not rule out on heterozygous cells unless it is Kell and we don't have a homozygous Kell cell on an indate or expired panel. In the case of Kell the techs have to have 3 heterozygous cells to rule it out. We have seen many times where someone has ruled out on heterozygous cells and missed an antibody because of dosage. With a large sickle cell population this is not good. :(

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I also agree with Malcom on the dosage issue-that is why I stated in my post that at the end of the day you still have to use your brain. If you have had to use heterozygous cells to rule out you want to be sure that you are not missing a dosing antibody. And yes there are certain antibodies that you would never rule out using heterozygous cells.

That is why we get paid the big bucks - right??!!

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