I thought I read somewhere--is there a regulation about using two A2 cells when typing with the A1 lectin?

Can't seem to find --

 

I can't think of a reason why, unless you take into account the relatively large range of A antigens per red cell there is for A₂ red cells (160, 000 to 440, 000), which means that a red cells from an individual with 444, 000 A antigens per red cells may just about give a weakly positive reactions with some examples of Dolichos biflorus?

Limper55,  I just looked at the package insert for anti-A1 Lectin and can't find anything in it that stipulates that you use two different A2 cells, but our procedure and a continuing education course from the Red Cross on resolving ABO discrepancies says to test the patient's plasma with at least 2 A2 and A1 cells.  The package insert does say there is no US standard of potency, so maybe that's it.

mollyredone, are you certain that ARC are saying that two of each should be used with the anti-A₁ grouping reagent, and not that at least two of each should be used against the patient's plasma, to see if there is an anti-A₁ in the plasma, and not, for example, an anti-M?

I'm not aware of any regulation, but I suspect this idea might come from trying to satisfy the old 3 positive/3 negative statistical application of Fisher's method to get your magic p value of a 1/20 chance that your conclusion is incorrect. I read (or heard) long ago that since our reagent A1 cells and A2 cells are pools from at least three donors, they (in a Mickey Mouse sort of way) meet this.

 

 

I don't know what the regulations say, but if you are typing with anti-A1 in order to distinguish between A1 and A2, I would always test with an anti-H in parallel.  Bearing in mind that the most logical reason for using an anti-A1 in the first place is to sort out an ABO grouping discrepancy, you would want to cover the eventuality that you might have something other than an A1 or an A2 - and you need adequate controls!

When I use the A1 lectin I run A1 and A2 cells as controls.  Are you talking about an A1 lectin produced by the Red Cross?

HI--thanks so much!

The AABB  Technical Manual (17th Edition) page 883-says to use several examples--that's where I I got that in my head.

Thank you everyone.  I appreciate this board and your help. 

 

One time you would use two A2 cells would be when you are cross-checking your reagent -- use the old lot of cells and also test against the new lot of cells as well as the negative control cells to verify that nothing happened to the reagent in shipping, etc.

Malcolm, I did say to use two types with the patient's plasma, not with the Anti-A1 plasma.

My apologies mollyredone.  Put it down to old age and failing eyesight!!!!!!!!!!!!!!!!

No worries!  And I should have said anti-A1 reagent not plasma!