Cord Blood

[verajerdon]

Two days ago a tech put in that a cord blood was negative and two days later the Doctor calls and asks for it to be rechecked. So we test from the same cord blood tube it was a 2 plus positive. The original tech swears that it was negative and they tested it right after they recieved it and even double checked it. The original tech also redid the specimen today on the same tube and saw that it was now a 2 plus reaction. This also happened with another tech on another shift. They called one negative and a Doc called five days later and asked for it to be rechecked. In that case it something like a 4 plus positive. Is it possible that the reaction is showing up stronger after the specimen is getting older???

[bossgirl05]

Storing it in the fridge can cause it to be positive for complement.

[Malcolm Needs ☆]

Storing it in the fridge can cause it to be positive for complement.

Well, it can, unless the sample is anticoagulated by EDTA, and, don't forget that cord blood does not have the full wack of complement anyway.

It is much more likely that the antibody on the red cells is either a "cold" reacting IgG or an IgG of wide thermal range, such as ABO. It is not that unusual for HDN caused by amternal ABO antibodies to give a negative DAT immediately after birth (the same can be said for some Gerbich antibodies, but antibodies against Gerbich antigens are very rare).

:confused::confused:

[AMER]

What about the technical error for example washing the cells may be one of the tech did not wash the cells????????

[David Saikin]

I would think that maternal ABO abs have had a chance to react with the cord cells "in vitro" . . .

[profbaud]

Cord bloods are very stable specimens. I think the washing procedure needs to be checked out. If this is not adequate for the DAT, you can get a false negative. I take it this was done by tube method and not in Gel? DAT testing for cord bloods only requires using Anti-IgG AHG, and since the specimen should be an EDTA tube, complement is not an issue. Technical error is!

[verajerdon]

We do not test are cord bloods using a EDTA purple top tube we get the cords in a blue cord blood tube. We have a cell washer and we even add extra manual washing steps so I do not believe that to be the issue. The same tech with the previous negative results came back in and repeated the test exactly the way they did it that day and got a positive result.

[John Eggington]

Did you test the cells with monspecific AHG reagents and/or perform an elution?

[Malcolm Needs ☆]

Yes, that is why I was thinking along the ABO route (and good point about the eluate John - but, of course, the eluate would have to be tested against A and B cells, as well as the normal group O panel - otherwise this would be negative too, if no other maternal antibodies are present - that is, assuming ABO).

[John Eggington]

A and B cells seem to be an underused resource, when it comes to antibody identification.

[Malcolm Needs ☆]

Couldn't agree more.

By the way, welcome to BBT Mr. Egg Sir; I, for one, am really glad to have you "on board".

[JOANBALONE]

I like David's theory. It would be easy to test this theory in the lab.

JB

[John Eggington]

Took my time, but here now. Thanks for the welcome.

[Yanxia]

I am very interesting in this question. I guess it is because wallonton gallon( I think I spell it wrongly, but please forgive me and tell me the correct spelling if you can understand what is my meaning) on the cord blood cells. But you say it is washed.

Please tell us what the test if for, anti-D or DAT? And the method you use?

I can't imagine any reason to cause this just from my knowledge except personal error. I know you will not agree with me, this is just my view .

[Yanxia]

I have another guess, maybe it is because the antibody is too more to form visible coagulation. When you store the specimen in the frigerator few days later, the antibody on the cell surface will decrease and we can get the positive reaction. I think it is likely on the second case which is 4+ plus reaction. As my post before, this is just a daring guess.

[Malcolm Needs ☆]

I am very interesting in this question. I guess it is because wallonton gallon( I think I spell it wrongly, but please forgive me and tell me the correct spelling if you can understand what is my meaning) on the cord blood cells. But you say it is washed.

Please tell us what the test if for, anti-D or DAT? And the method you use?

I can't imagine any reason to cause this just from my knowledge except personal error. I know you will not agree with me, this is just my view .

Hi Yanxia,

I think you mean "Wharton's jelly", but I may be wrong.