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Would love to know the explanation


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Two things I'd like to be able to explain to my students:

1. Retic separation: I understand that patient retics have a lower specific gravity and will thus end up at the top of the column of cells. But there must be retics in the transfused donor cells as well. How come they don't end up mixed in there with the patient’s retics? Is it that they are several days older, and, if so, what does that do to them that makes them denser?

2. Lui freeze-thaw elution: I get how low pH and organic solvents will drive antibody off of cells. What is the mechanism, though, whereby freezing and thawing will do the same? I would think you'd end up with antibody still stuck on bits of red cell stroma.

Inquiring minds want to know. Thanks - Phil

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I can give you the "Delores Mallory" explanation to retic separation. We all believed her :)

 

You have 2 points working in your favour. 1. The patient's retic rate has increased due to their blood loss/ anemia. 2. The dilution of the donor blood which should have a normal retic count at most, produce a very low ratio of transfused retics to patient retics.

 

While you may get an occaisional donor retic, it will not be enough to bias your phenotype results. If you do see a significant mixed field, you can assume it is due to the patient either not reticing or a 50% or more replacement of patient blood volume. And we know harvesting retics after recent, large transfusions, is a risk we often should not take. Particularly when we now have genotyping available.

 

Hope this helps

Edited by Pony
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Thank you Pony, very good points. And it was basically a "how come" question anyway. I really don't have a problem interpreting mixed field typing results when there's a smattering of donor cells in there that you may only be able to see microscopically. I had a delayed rxn due to anti-Jka + E the beginning of the week that presented just like that. It can become a grey area, though, when you have no choice but to take that risk: the more blood they've received, if the antiserum you're using gives you a weak 2+ under the best of circumstances instead of a whopping 4+ , if you have no pretransfusion sample to test, if you really need immediate accurate typing results to try to unravel your ID puzzle, and/or genotyping may not be readily available.

Edited by Dr. Pepper
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  • 2 weeks later...

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