Direct Coombs in GEL

[Brenda K Hutson]

If this was previously covered, my apologies; I did try to search and see (ha, knowing me, I previously posted this question )

Again, not being familiar with any testing in GEL other than the Antibody Screen and Antibody Panels.....what would everyone say about DAT Testing in GEL (IgG and C3)?

Thanks,

Brenda Hutson, CLS(ASCP)SBB

[Malcolm Needs ☆]

We do it all the time now. Rarely, we will perform them in tubes - but that is really, really rare.

[David Saikin]

I use the IgG cards and the buffered gel with anti-C3b,-C3d. You can get poly cards - I don't do enough to warrant their purchase.

[Mabel Adams]

What testing I did of the IgG cards, I think they are more sensitive than tube. If you test all non-O babies of O mom's you will probably find even more positives, for instance. I wasn't entirely sure that I usually needed a DAT test that was more sensitive than tube. My testing of it was fairly limited and nearly 10 years ago.

[tbostock]

Same as Mabel; when we went live with gel many years, we very quickly found that the DAT was way too sensitive. All of our dialysis patients were always positive. So we went back to tube testing for the DAT.

Now we do them in solid phase (Tango), or in tube when the Tango is down.

[Generic]

Testing in the gel is much more sensitive than the tube. IME, a reaction as strong as 2+ in the gel can still show up as negative in the tube...

[Liz]

Routinely perform gel; however, if you are not sure of a positive result (it doesn't make sense to you) then go to the tube and if it was rouleaux formation it will nicely wash away.

[mia9941]

Routinely perform gel; however, if you are not sure of a positive result (it doesn't make sense to you) then go to the tube and if it was rouleaux formation it will nicely wash away.

We use ORTHO gel on the Provue for all DAT's and often will obtain a reaction the instrument requires to be read manually. This is frequently found on cord's. BB policy is that if the gel is positive then there is no because it is a less sensitive test. However, there have been cases where the DAT is weakly positive with gel, but negative on tube. Our Supervisor says we are not to do further testing on weakly positive gel DAT's because if the gel says it's positive, then it's positive. I don't necessarily agree that this policy is the best practice. A positive DAT throws our nurses into a possibly unnecessary tizzy. Your thoughts would be appreciated.

[Likewine99]

We've done DAT testing in gel for years and love it. We use IgG and poly cards, C3 testing in tube. Techs who are not dedicated to BB like it. I would say look into it, what do you have to lose? We do our cord DAT's in IgG gel, works just great.

[sblanchard]

We do Poly and IgG DAT's on the Provue (interfaced w/ BB application) and use tube for the C3.

Have not had any problems. We also do IgG DAT's on our Cords.

[Joanne P. Scannell]

We test both Anti-IgG and Anti-C3bd Direct Coombs Tests in gel.

Very clear results.

Validated this and found sometimes the reactions are stronger in gel (sometimes not), so we did notify the physicians about the change.

[yiams]

I'm just getting to thread a little late. For those of you using buffer cards to perform anti-C3d,-C3b testing, how do you set this up? My assumption would be 50 uL of 0.8% RBCs and 50 uL of anti-C3b,-C3d. Do you place the cards in the centrifuge immediately or do you allow them to stand for 5 minutes before spinning?

thanks,

[Joanne P. Scannell]

12.5mcl of 4% cell suspension

25 mcl of Anti-C3b/d

Incubate at 20-22oC for 5 min.

Spin, etc.

[Deny Morlino]

Same here as Likewine99

[David Saikin]

I use 50uL of 0.8% cels and 25uL of anti-C3b,-C3d/ Incubate for 5 minutes/ spin

[Liz]

We use ORTHO gel on the Provue for all DAT's and often will obtain a reaction the instrument requires to be read manually. This is frequently found on cord's. BB policy is that if the gel is positive then there is no because it is a less sensitive test. However, there have been cases where the DAT is weakly positive with gel, but negative on tube. Our Supervisor says we are not to do further testing on weakly positive gel DAT's because if the gel says it's positive, then it's positive. I don't necessarily agree that this policy is the best practice. A positive DAT throws our nurses into a possibly unnecessary tizzy. Your thoughts would be appreciated.

If you are using a polyspecific AHG you will want to see if it is IgG and/or Complement. And if it is a weak reaction (or strong) and you are in doubt check for rouleaux. Yes it may be a true weak positive but you must be sure. So have a look under the microscope. I am not saying that the tube is correct over the gel but it allows you to have a look under the microscope...

What did you want to say in what I highlighted above?