Hi Everyone 

I am currently studying and decided to do some ABO experiments with patient samples but with some odd results. Wondering if anyone could shed some light ? 

I cross matched a mix of incompatible red cells with patients plasma to see if there would be a difference in strength of ABO incompatibility.

The AB and B red cells with the group A plasma gave negative results ? 

AB red cells with group B plasma was positive I.e. a group B patient being cross matched with AB red cells 

All samples were Rh D positive to avoid any incompatibility with that issue.

I also repeated them with the same samples and got the same results.

Thanks

Moira

Did you incubate at 37?  Did you consider clinical conditions? 

Yes 37 incubation an patients I selected just pre op samples previously tested nothing out of ordinary ?

Would you mind telling us what technology you were using (tubes, column agglutination technology, solid phase. etc)?

Human Anti-A typically have a high titer as where Anti-B are usually weaker.  Correct me if wrong, but I believe this is the reason for allowing GroupA plasma usage for emergency massive transfusion for most trauma hospitals now.  Big AABB article sometimes in the end of 14' or early 15' about this.

Edited July 13, 20169 yr by yeleng22
MTP added

Hi Malcolm CAT. I repeated with positive result. Sample I remixed and centrifuged an tested again when at room temperature. ? Anti-HI cold sample issue ? Or Secretor rule ? Will read more on that topic yeleng 22 

Thanks for feedback 

sugar sugar

On 8/2/2017 at 3:03 PM, mrmic said:

sugar sugar

?

ABO antigens are basically sugars structures.   The development and expression of these antigens and antibodies are controlled by various genes an individual inherits.  The antibodies are also possibly produced based on the various "natural" exposures to similar antigens in the environment, gut, etc. and the immune system functionality of the antibody producer.  (or in the case of commercial antisera, the particular antibody producer(s) or cell line(s) used to produce the antibody can vary from manufacturer to manufacturer).   Actually, as I ponder this, maybe all antigens/antibodies are effected by some of the same processes......

Therefore, in my humble opinion, the strengths of the agglutination reaction within in any one test method, maybe affected by these factors as well as the method itself.

If everyone was group O it would be nice for Blood Bank ................. but what's the adventure in that?  Variety is the spice of life!

 

Some individuals have very low titer/affinity antibodies, and this probably explains your negative results.  Not all that surprising or uncommon.

Not mention that isoagglutinins may be absent entirely in the first half year to year of life, and in patients receiving intensive immunosuppressive/myeloablative therapy.  So the source of your plasma may make a difference, if it was from patients in a hospital, as opposed to healthy blood donors.

Another reason why our computers are better at selecting ABO compatible units than serological testing is.

11 hours ago, Mabel Adams said:

Another reason why our computers are better at selecting ABO compatible units than serological testing is.

Just SO true Mabel.

Don't know if someone mentioned this idea earlier, but did you try serum?  Reactions may be inhibited or weak if using EDTA plasma. 

14 hours ago, R1R2 said:

Don't know if someone mentioned this idea earlier, but did you try serum?  Reactions may be inhibited or weak if using EDTA plasma. 

Would you explain this please? Thanks

It is because serum would have Ca⁺⁺, Mg⁺⁺ and Mn⁺⁺ ions present (needed to activate the classical complement pathway beyond initiation), whereas EDTA will, in effect, remove these ions from plasma by chelation.

An ABO mis-match is far "easier" to detect using serum than plasma, and may even lead to haemolysis of the test cells, however, in both cases, IF the plasma of the proposed recipient has high levels of Type 1 ABO antigen (the ABO substance that is soluble in the plasma/serum - in other words the proposed recipient is a "strong secretor"), there is a slight danger, albeit slight, that this ABO substance may inhibit the reagent anti-A and/or anti-B, causing false negative results.

6 hours ago, Malcolm Needs said:

It is because serum would have Ca⁺⁺, Mg⁺⁺ and Mn⁺⁺ ions present (needed to activate the classical complement pathway beyond initiation), whereas EDTA will, in effect, remove these ions from plasma by chelation.

An ABO mis-match is far "easier" to detect using serum than plasma, and may even lead to haemolysis of the test cells, however, in both cases, IF the plasma of the proposed recipient has high levels of Type 1 ABO antigen (the ABO substance that is soluble in the plasma/serum - in other words the proposed recipient is a "strong secretor"), there is a slight danger, albeit slight, that this ABO substance may inhibit the reagent anti-A and/or anti-B, causing false negative results.

Yes, what he said.....

It's one of the reasons that washing patient cells before testing is one of the steps in resolving an ABO discrepancy.

Scott

21 minutes ago, SMILLER said:

It's one of the reasons that washing patient cells before testing is one of the steps in resolving an ABO discrepancy.

Scott

Absolutely right Scott.

On 2018/1/11 at 3:30 PM, Malcolm Needs said:

It is because serum would have Ca⁺⁺, Mg⁺⁺ and Mn⁺⁺ ions present (needed to activate the classical complement pathway beyond initiation), whereas EDTA will, in effect, remove these ions from plasma by chelation.

An ABO mis-match is far "easier" to detect using serum than plasma, and may even lead to haemolysis of the test cells, however, in both cases, IF the plasma of the proposed recipient has high levels of Type 1 ABO antigen (the ABO substance that is soluble in the plasma/serum - in other words the proposed recipient is a "strong secretor"), there is a slight danger, albeit slight, that this ABO substance may inhibit the reagent anti-A and/or anti-B, causing false negative results.

Thank you very much for the explanation.

Just a little confusion how do the  Ca⁺⁺, Mg⁺⁺ and Mn⁺⁺ ions infect the agglutination? does it because the complements can enhance agglutination or because the complements caused haemolysis is a sign of ABO mis-match?

 

It is the latter yan xia.

The various metal ions have no effect on either sensitisation or agglutination, but, are vital co-factors for the complete initiation of the classical complement pathway (C1qrs), leading to the membrane attack complex (MAC), and it is this MAC that allows haemolysis to take place, and it is this haemolysis that allows the Hb to escape from the red cells, which we see as a pink/red colour in our tests, which equates to a positive result.  As the classical complement pathway is a huge amplification system (one C1qrs complex, for example, results in the generation of some 8, 000 C3b molecules), it makes the test very sensitive indeed - much more so than just looking for agglutination.