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Checkcell (weak) vs. DAT/IAT and other reagents


Clarest

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I was checking the insert of Checkcell (weak) for revising our SOPs and found that it does not specify the reaction strength after adding Checkcell for validating the test. I don't know where I got this in my mind that in order to validate a negative DAT or IAT test, after adding Coombs Control cell (Checkcell?) the reaction strength should be at least 2+ or above?! I also went to check the insert of AHG reagent and it says that any negative or weak positive result obtained after using AHG reagent should be validated with IgG-coated cells, although they didn't specify how weak is weak pos (less than 1+?). I want to know how many of you add IgG-coated cells (or Coombs control cells or Checkcells) to weak positive DAT/IAT test?

 

Regarding some of other cell reagents, their inserts mention that "Store (the reagent) at 1-10C when not in use".  Does it mean we do not need to warm up the reagent to room temperature before using it for the test? I am just wondering where you put your routinely in-use reagents (always in the fridge?). How about the antibody screen/panel cells reagents? Do you always warm them up to room temperature before use?

 

Thank you for your input.

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Hi,

 

First, regarding weak positive DAT/IAT; we confirm them under microscope and use check cells with them. Our weak reactions are taken as less than 1+. And you are right about having 2+ reaction after adding check cells although i also dont remeber the source of the info. Anyways I am gonna check this out.

 

About storage of coombs reagents and panel cells, we dont "warm" the reagents before use but just let them stand for couple of minutes to come to room temperature befroe testing. We use poly specific coombs reagent (IgG & anti C3d) so we only warm the coombs reagent if using pre warm technique.

 

Hope this helps

regards

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Immucor says the reagents for the Echo are supposed to be out of the fridge for 20 minutes prior to testing. I would think that time would work for tube reagents as well if you want a specific time recommendation. I confess that I have been known to push that a little for tube blood types. For antibody screens I make sure everything is warmed up - saves me time in the long run if I don't have to chase cold reactive antibodies.

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I'd be curious to see a reference to "needs to be 2+ following addition of confirmation cells."

 

So would I - my check cells are invariably 1+.  AABB standards just state that a method of control appropriate to the system in use needs to be employed.  If you have a negative rx at ahg and your check cells are macro positive I would think that you have validated your antiglobulin rx.

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Thanks to you all for replying my post. I actually called the manufacture regarding the reaction strength after adding check cells and they said we should expect at least 2+ reaction. Then, I asked them for a reference for that and haven't got back from them.

Regarding the temperature of reagents, I think it's very hard to practice in reality. If I ask my staff to make sure the reagents reach room temperature before adding them to test tubes, they would probably just leave the reagents on the bench all the time. They are busy and within one shift they may need the reagents several times. I really cannot expect that every time they remember to bring the reagent out of fridge 20 minutes before they add it to the tube. Right now, we have two racks of ABO/ Rh reagents and alternately use them on different shifts, but not able to do this  for Ab.screen or panel cells reagents.

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Don't understand how Check cell reactions can be graded as 1+, 2+, 3+ or 4+? Technically all Check cell reactions are "mixed-field". In an negative antibody screen tube (with reactive anti-antiglobulin reagent), there is one drop of unagglutinated antibody screen cells and one drop of agglutinated Check cells.

Back in the old days using paper worksheets, we used a check mark to indicate "macroscopic agglutination" observed after addition of check cells to a negative antiglobulin test.

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I really cannot expect that every time they remember to bring the reagent out of fridge 20 minutes before they add it to the tube. Right now, we have two racks of ABO/ Rh reagents and alternately use them on different shifts, but not able to do this  for Ab.screen or panel cells reagents.

 

Why not? Every lab is busy - I work in the tenth busiest hospital in the Uk and we still manage to do it. We just set a timer and walk away so we don't forget. You can even clip the timer to your pocket so you aren't leaving it for someone else to deal with. Staff should follow good practice procedures - rubbish in, rubbish out... It creates a lot more work to investigate nonsense reactions that simply leaving the reagents on the bench for a bit.

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