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antibody Detection: 3-cell vs 2-cell screen


tlorme

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If you do antibody id's a 3 cell screen gives you more info than a 2 cell. If you don't do abids then a 2 cell is fine. The antigen structure of a 3 cell screen should guarantee homozygous cells in the Rh, Fy, Jk, and MNS systems. I don't know if the 2 cell can do that (but I haven't used a 2 cell screen in decades).

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We use 3 cell because of the guaranteed homozygosity for Rh, Fy, Jk, and MNSs. I have sales people trying to sell me on saving money by going to a 2 cell screen, but we do lots of antibody identifications and there are many times you can use that extra cell in the ID.

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Assuming you have the antigens covered that show dosage, I am not sure that there is much of an advantage by adding one more screening cell. If an unexpected antibody is present, chances are that one extra cell is not going to take care of all of your rule-outs anyway.

That said, we do use a 3-cell screen, but we also use a 3 rule-outs / rule-ins rule, including a homozygous where appropriate.

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A lot depends on whether you are testing donors or patients. For testing patients it's important to find weak examples of antibodies that sometimes only show up when there is homozygous expression of the antigen on the screening cells. It's almost impossible to guarantee that when you have a set of only 2 cells; therefore three cells, sometimes even 4 cells are used. For donors, it's not so important to find those weak antibodies and therefore most countries consider that for testing donors, the homozygosity is not needed; therefore it's OK to use two cells. It's got nothing to do with testing in a manual system or an automated system

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TheFDA has very few requirements for screening cells. The FDA requires that screening cells musthave a positive cell for D, C, c, E, e, K, k, Lea, Leb,Fya, Fyb, Jka, Jkb, P1, M, N, S, s and has no requirmentsaround homozygosity. Either 2 cell or 3 cell screening cells are licensedfor use in antibody detection, so that takes you back to defining thefacilities’ requirements – do you believe you need homozygous cells, likelydemonstration of a negative cell with screening results, do you want to do moretests per centrifuge head, or a thousand other reasons you might have to selectone over the other.

I’dsay I’ve come across an equal number of passionate folks about the selection ofone over the other, and I’m not sure that either group is particularly right orwrong (although many in either group would disagree), then there is a smallergroup of folks who don’t think it matters that much and have determined thatthey would use a 2 cell or 3 cell screen based on some random factor – price,what was in place, what fits in their bench rack, ...

I think the real decisionpoint is that you understand what the pros and cons are for your particularneeds and you understand the limitations of your choice – all the things thatmake you a good blood bank.

Don't know if my ramblings helped but hope it at least gave you an opportunity to consider. Jeanne :blahblah:

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TheFDA has very few requirements for screening cells. The FDA requires that screening cells musthave a positive cell for D, C, c, E, e, K, k, Lea, Leb,Fya, Fyb, Jka, Jkb, P1, M, N, S, s and has no requirmentsaround homozygosity. Either 2 cell or 3 cell screening cells are licensedfor use in antibody detection, so that takes you back to defining thefacilities’ requirements – do you believe you need homozygous cells, likelydemonstration of a negative cell with screening results, do you want to do moretests per centrifuge head, or a thousand other reasons you might have to selectone over the other.

I’dsay I’ve come across an equal number of passionate folks about the selection ofone over the other, and I’m not sure that either group is particularly right orwrong (although many in either group would disagree), then there is a smallergroup of folks who don’t think it matters that much and have determined thatthey would use a 2 cell or 3 cell screen based on some random factor – price,what was in place, what fits in their bench rack, ...

I think the real decisionpoint is that you understand what the pros and cons are for your particularneeds and you understand the limitations of your choice – all the things thatmake you a good blood bank.

Don't know if my ramblings helped but hope it at least gave you an opportunity to consider. Jeanne :blahblah:

I find it mind-numbingly incredible that the FDA do not worry about the zygosity of antigens such as S, s, Fy(a), Fy(B), Jk(a) and Jk(B), when clinically significant antibodies that show dosage for these antigens are (comparatively common), and yet do worry about things like Le(a), Le(B) and P1, where the antibodies are (almost) universally NOT clinically significant.

That news just stuns me.

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I find it mind-numbingly incredible that the FDA do not worry about the zygosity of antigens such as S, s, Fy(a), Fy(B), Jk(a) and Jk(B), when clinically significant antibodies that show dosage for these antigens are (comparatively common), and yet do worry about things like Le(a), Le(B) and P1, where the antibodies are (almost) universally NOT clinically significant.

That news just stuns me.

Many of us are in the same boat but remember the FDA requirements are "minimum" requirements and it is perfectly acceptable to exceed them. As well because these are laws, they do not change often and reflect the knowledge and beliefs at the time they were created. They are not frequently updated because of the difficults in making those changes.

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