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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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The challenge becomes as a few have mentioned the scarcity of some homozygous cells in certain situations, ie)presence of  anti-D in a rr patient It is impossible to find homozygous cells for E, C , etc in this situation. I am having a " debate" of sorts :)(!) regarding the need to run 2 hetero in this situation, as it appears most of you have mentioned. The bigger questions is what do you require In these situations?

Would love BBtalk to start a new voting grid as has been done here- to address the questions of ruling out E, C in presence of anti-D)-how do you approach the homozygous challenge in this instance? 2 hetero? (Btw-bloodbank talk, the grid above  should have included 3 homo-I have had blood bankers in my past insist on this)! Impossible often with multiple antibody situations.

 

 

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26 minutes ago, JustaKIDD said:

The challenge becomes as a few have mentioned the scarcity of some homozygous cells in certain situations, ie)presence of  anti-D in a rr patient It is impossible to find homozygous cells for E, C , etc in this situation. I am having a " debate" of sorts :)(!) regarding the need to run 2 hetero in this situation, as it appears most of you have mentioned. The bigger questions is what do you require In these situations?

Would love BBtalk to start a new voting grid as has been done here- to address the questions of ruling out E, C in presence of anti-D)-how do you approach the homozygous challenge in this instance? 2 hetero? (Btw-bloodbank talk, the grid above  should have included 3 homo-I have had blood bankers in my past insist on this)! Impossible often with multiple antibody situations.

 

 

Personally, I think people are getting a bit "hung up" about this - not least the people who "write the rules", and I think that a lot of these problems are caused by the sloppy use of nomenclature (see my first ever post on BloodBankTalk back in March 2009 - before it became PathLabTalk).

When you are using antibody screening red cells, you are using, I presume, R1R1, R2R2 and possibly rr red cells, but are you actually?  These are "most likely genotypes", that are derived from phenotypes, but I very much doubt if the donors, from which these red cells have been derived, have been genotyped.  Even if they have been genotyped, it is extremely unlikely that full gene sequencing has taken place on the RHD and RHCE genes to determine, whether either the RHD gene is present in a homozygous state, a hemizygous state, or a heterozygous state, where one RHD gene is of the wild type and the other is mutated, and would produce a variant D antigen. or the RHCE gene is homozygous for the production of, in order, the C and e antigens, the c and E antigens and the c and e antigens, or whether they may be hemizygous with a silent gene (either with a normal RHD gene to encode a D-- or D.. haplotype, or with a silent RHD gene to encode an Rhnull haplotype), or whether they may be heterozygous with, for example, a normal C and e antigen and a CeS antigen in, for want of a better way of putting it (although this, strictly speaking, only applies to genes, rather than antigens) in trans.

The same principle applies to all of the other antigens and their genetic backgrounds.

So what am I saying?

I am saying that, day after day, we are excluding the presence of an anti-D, an anti-C and an anti-E (and, possibly, an anti-f) with screening cells that we actually do not know what antigens they are actually expressing, and yet we do not worry about this.  It is only when we detect a reaction with the screening red cells that we bother to perform an antibody investigation to determine the specificity of the antibody causing the reaction.  What, I ask, does this say about our logic?  I would contend it says nothing flattering!  So, if you are detecting an anti-D, and you (that is the collective "you", JustaKIDD, not a personal "you" - I am certainly NOT attacking you as an individual) are worried about the presence of an anti-C or an anti-E, because you only have one example of r'r or r"r red cells to exclude the specificities, I, unlike the people who "write the rules" would say "so what", but, if you are worried, why not just assume the antibody/antibodies is/are present, and cross-match rr units (if, indeed, the red cells in the bag actually ARE rr :devilish::devilish::devilish::devilish::devilish:).

Lastly, in all the years since anti-C and anti-E have been described (1941 and 1943 respectively), how many patients, with anti-D in their plasma, have had a fatal transfusion reaction due to the presence of an undetected anti-C and/or anti-E?  Not many (if any) I would suggest, and yet we, as a whole, get ""hung up" about such things, for no apparent reasons.

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On 05/10/2016 at 4:43 PM, Dansket said:

We will rule out C and E in the presence of anti-D with a single C+c+ or E+e+ cell.  K may be also ruled out with a single K+k+ cell.

So would u rule out the C and E if the anti-D reactions were not conistant in strength ? And would this apply only to the IAT or papain (enzyme) non reactive panel cells or both ? Could dosage not occur in that instance?

Thanks

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We use the rule of 3. Three homozygous to rule out and 3 positive cells to rule in. IF PISSIBLE 

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16 hours ago, CSP0102 said:

We use the rule of 3. Three homozygous to rule out and 3 positive cells to rule in. IF PISSIBLE 

I would think that one can only use this method to rule out if the patient is a secretor.

Scott

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Are there any rules for ruling out P1 with the different antigen expression strengths? 

Thanks

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One way of ruling IN anti-P1 is to incubate the panel at room temperature and below, in particular with papain-treated red cells.  This will lead to much stronger reactions if the antibody is an anti-P1.

Another is to inhibit the anti-P1 with either pigeon egg white (difficult to come by) or pigeon guano (difficult to avoid - particularly in Trafalgar Square!).

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3 homozygous cells, unless we are ruling out C or E in the presence of anti-D. In that case we use 3 heterozygous rule outs.

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Homozygous unless demonstrating anti-D (heterozygous C, E).

With anti-c or anti-e, uncomfortable with ruling out E, c on heterozygous cells.  Would prefer to type the patient (if possible) and give phenotypically similar.

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Red cell antigens CANNOT be homozygous, heterozygous or hemizygous.  This term refers to genes, and red cells have no DNA.  At best, they can demonstrate homozygous, heterozygous or hemizygous EXPRESSION of an antigen.

I know, I know, I'm a pedant!

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1 minute ago, Malcolm Needs said:

Red cell antigens CANNOT be homozygous, heterozygous or hemizygous.  This term refers to genes, and red cells have no DNA.  At best, they can demonstrate homozygous, heterozygous or hemizygous EXPRESSION of an antigen.

I know, I know, I'm a pedant!

And don't you be doin' no computer crossmatches with those homozygous RBCs neither!

Scott

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Sooooooo.........is is 1 positive reactive cell out of 3 selected cells ok?  What next?  Do you keep testing "homozygous or heterozygous" selected antigen positive cells til you get 3 negative?    It's not just rulling out, it's looking for what's in.    It is a good thing to have a Immunohematology Reference Lab partner to assist with multiple antibodies or antibodies to antigens of high frequency.  Your blood supplier should have this service for you...  Probability calculations do not always go hand to hand with antigen expression.

🐀 mic

 

 

 

 

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