I am in the process of evaluating performing cord blood testing on gel. We perform ABO/Rh type and DAT on babies born to type O and Rh Negative mothers. Our current testing is by tube and the DAT is evaluated microscopically. I was concerned that we might end up with more positive DATs in gel, but I'm finding the opposite! Almost all of the positive DATs with weak (microscopic) reactions are coming up negative in the gel (IgG).

If we convert to gel and "miss" these weak reactions, will that be significant? Do others read DATs microscopically? Are any of you doing Cord Blood testing in gel?

We used to read our cord DAT's microscopically.....switched to gel 7 years ago. I generally find the gel is more sensitive than tube, for our adult DAT's before we do an eluate we evalute the tube DAT to see if it will be worth our while. Often a 1+ IgG DAT in the gel is weak microscopically in the tube. I can't see cords being much different.

As far as missing anything significant - what would a weak DAT in a baby equal clinically ..... I doubt very much - there can be jaundice in a baby with a negative DAT too!

Hi there,

while reading your answer on "gel technique", one doubt came to my mind..

How do we say whether the gel technique is not giving "false positivity" or the manual technique is giving "false negativity", in weaker reactions ?

I had attended a meeting some years back, wherein a consultant had presented the finding of "false negativity" in manual method...But why cant it be in the other way round ? any references ?

any input would be appreciated....

Excuse me, which brand of gel are you using? Also, did u wash the cells once with the commercial diluent before making up the cell solution for the gel?

We do cord DAT's routinely in gel on babies from type O, Rh neg, or clinically significant antibody moms. I have been here 6 months. I have not heard any complaint where the doctor is confused by a negative DAT when he feels it ought to have been positive given the clinical picture.

We perform an ABO/Rh and DAT using Otho's gel system on all babies born to group O moms and Rh negative moms. Our OB dept handles about 1500 deliveries/year.

We wash the cells one time with saline prior to loading the gel cards. We have been using gel since it's beginnings back in the 90's and the staff feels that the IgG in the gel card is "more sensitive" than the tube reagents.

We do perform weak-D testing on these babies if Rh negative, also done in gel (we validated this procedure on-site) prior to use.

We have not had any physician concerns re: DAT results performed with this method.

How did you validate doing Weak D in the gel?? We use gel but have been doing tube Weak D testing. We haven't found a weak D in a cord blood since going to gel. They've all been negative.

We had an adult sample and a donor unit that was AB, weak D-pos (two separate occasions), that both tested neg w/tube anti-D and was weak D pos in tube testing. We tested this same pt and donor unit in an ABD gel card and got 3+ pos in the anti-D well, verifying that the pt and the donor are truly D pos.

We use an IgG gel card, make a cell suspension like we were doing at DAT in gel, add 50 uL cell suspension to the card, add 25 uL tube anti-D reagent, incubate for 15 min then spin. This pt tested weak D pos (3+) with this methodology and the donor unit also.

We have also validated Fya typing in gel cards, same scenario as above and using

25 uL anti-Fya. We tested 10 patients and 25 donor units in this validation, comparing it to tube testing.

None of our cord bloods have ever tested weak-D pos in gle but we don't even own a cell washer so on the rare occasion that we have an Rh neg cord blood we do this procedure.

On 5/28/2008 at 7:14 AM, csjuarez said:

I am in the process of evaluating performing cord blood testing on gel. We perform ABO/Rh type and DAT on babies born to type O and Rh Negative mothers. Our current testing is by tube and the DAT is evaluated microscopically. I was concerned that we might end up with more positive DATs in gel, but I'm finding the opposite! Almost all of the positive DATs with weak (microscopic) reactions are coming up negative in the gel (IgG).

If we convert to gel and "miss" these weak reactions, will that be significant? Do others read DATs microscopically? Are any of you doing Cord Blood testing in gel?

I know this post is about 15 years old, but I recently came across a similar issue. I have always done DATs in tubes.  But currently switched to gel.  I am use to washing the cells when I do a DAT. I find it kind of odd that the package insert for the IgG cards doesn't include washing in it's procedure.  Do anyone know exactly why?   The insert said just to straight add 10uL of packed cells to 1.0 mL of your MTS diluent to get your 0.8% cell suspension.  

 

I got a weak positive reaction on a baby cord blood. I decided to wash the cells and the reaction came out stronger. Then I repeated this 2 more times and got similar results (see picture).  All controls were negative.

 

Has anyone experienced this ? And can I get your thoughts on this matter? Thank you so much, please have a nice day. 

 

 

 

 

I guess this may be caused by the Wharton's Jelly which can cause rouleaux formation of the cord cells. For the gel technique, it is good to test the adult cells without washing, but for the cord cells, maybe the Wharton's Jelly block  antigens on the cells' surface. I noticed that patients suffer from Multiple myeloma will not show false positive reaction in gel, but saddly I have not confirmed if there are false negative reactons.

No need to wash. We run Cord Bloods on our Ortho Vision.

Could it be contaminated saline, perhaps?

I would repeat using freshly prepared bottle of saline.

On 7/14/2023 at 9:05 PM, SbbPerson said:

I know this post is about 15 years old, but I recently came across a similar issue. I have always done DATs in tubes.  But currently switched to gel.  I am use to washing the cells when I do a DAT. I find it kind of odd that the package insert for the IgG cards doesn't include washing in it's procedure.  Do anyone know exactly why?   The insert said just to straight add 10uL of packed cells to 1.0 mL of your MTS diluent to get your 0.8% cell suspension.  

 

I got a weak positive reaction on a baby cord blood. I decided to wash the cells and the reaction came out stronger. Then I repeated this 2 more times and got similar results (see picture).  All controls were negative.

 

Has anyone experienced this ? And can I get your thoughts on this matter? Thank you so much, please have a nice day. 

 

 

 

 

I am so lazy that I just checked our IgG card today . I noticed it said that cord blood need to be washed before testing. I am at home now, I will attach the package insert tomorrow.

On 7/17/2023 at 7:44 AM, yan xia said:

I guess this may be caused by the Wharton's Jelly which can cause rouleaux formation of the cord cells. For the gel technique, it is good to test the adult cells without washing, but for the cord cells, maybe the Wharton's Jelly block  antigens on the cells' surface. I noticed that patients suffer from Multiple myeloma will not show false positive reaction in gel, but saddly I have not confirmed if there are false negative reactons.

Yes, I was thinking wharton jelly too. This was a cord blood sample. Thank you

Edited August 12, 20231 yr by SbbPerson

On 7/19/2023 at 11:34 AM, cthherbal said:

No need to wash. We run Cord Bloods on our Ortho Vision.

Could it be contaminated saline, perhaps?

I would repeat using freshly prepared bottle of saline.

 

 

I doubt it. We QC our saline in duplicate every day. Thank you for your input.

Sorry,I can't find the English version.The  underlined sentence means the cord blood cells needed to be washed at least once before testing.

Ortho MTS gel instructions say to wash if there is interference from clots, which may happen with cord blood, but it doesn't say to always wash cord cells before running a gel DAT.

On 8/12/2023 at 5:58 PM, Yanxia said:

My Chinese is a bit rusty, but if I am not mistaken, the underlined sentence states that we need to wash cord blood at least once before testing.  Sorry, I am just kidding, I don't know any Chinese, I just read Yan's explanation. 

I only wish I could know another language anywhere near as well as Yanxia knows English!  She has always impressed me with her blood bank knowledge as well.