Gel and tube discrepancy in antibody screen

[radwan1411 2]

hello, guys i'm having an issue with an antibody screening results of the donors 

i had an issue with couple of donors the first one he's an O+ , on the gel it gave negative ICT, but in the tube method it gave a positive P3 , identification is negative on tube method 

second donor was positive on the gel method, he's an A- , and the tube ICT was negative , tube identification was negative 

bio rad reagent used in the tube method 

and ortho diagnostics in the gel 

what's the possible causes of these results 

thanks 

Edited March 7, 2018 by radwan1411

[jalomahe 132]

In first scenario, Gel negative but tube ICT positive. Was the ICT positive on all cells or just some cells? Did you repeat both Gel and ICT screens to make sure there were no test performance errors. Did you test with with a different set of reagents to make sure reagents had not been contaminated?

In second scenario, basically same questions. However if you have reactions in gel with all cells then it might be an Ortho Enhancement Isoagglutination caused by the preservatives in the reagent cells. You can try repeating the antibody screen in gel using reagent cells that have been washed first to remove the additive.

[mld123 23]

I find that Gel screens are positive and tube are negative when there is either a Cold Antibody or Rouleaux.  Sometimes the gel finds an HLA that may not be picked up in tube either.  In all 3 of these cases, they are more of a nuisance then anything else.

[David Saikin 1,452]

I have found that if you have a gel rx <=2+ tube testing will be negative.

Your positive tube screen with a negative gel:  can't answer that one.

[John C. Staley 1,205]

I'm just curious, why are you doing both tube and gel on the same patient/donor?  Do you do it on every patient/donor or was this a special case for some reason?  

[radwan1411 2]

The ICT was done on the same donors twice not different donors 

and we do this two methods results comparison in our lab  and compare the results every 6 months and we picked up  on these donor this time 

the first donor case was resolved it was a cold antibody, I did a cold ICT using ortho surgiscreen on Reverse diluent cassette and patient sample with bliss no 37 incubation just room temprature incubtion and i was positive 

 

still resolving the second donor 

 

[John C. Staley 1,205]

Just to make sure I understand, this was done as comparison between 2 methods in use and you do this every 6 months.  How many samples do you compare?

[radwan1411 2]

Yes correct , 10 sample from each abo and rh, 5 negative ICT and 5 positive , 5 negative DCT and 5 positive , the both methods results must agree 

[galvania 811]

Every 6 months????  Why?  what are you hoping to prove?  What do you do if there is a discrepancy as above?  Switch methods??

[radwan1411 2]

Thats was in our laboratory policy as an indicator of quality control, for cap and aabb checklists, if there is a discripency as above there should be a corrective action after reaching to the result of the discripency 

[AMcCord 1,301]

20 hours ago, radwan1411 said:

Thats was in our laboratory policy as an indicator of quality control, for cap and aabb checklists, if there is a discripency as above there should be a corrective action after reaching to the result of the discripency 

Method comparison - apples and oranges in Blood Bank, but it makes CAP happy that you can check the box.

[jnadeau 46]

We started doing this every 6 months for CAP years back.  I now just assign 2 pos and 2 neg samples from our proficiency samples (AFTER the due date of course) and techs will perform in gel, PeG and albumin.  Reaction strengths vary of course but it keeps techs comfortable with the tube methods which we rarely use.

[R1R2 306]

There is no required number of samples to use for method comparison.   I would suggest 1 pos, 1 neg for Rh and antibody screen and pick your samples wisely - a nice strong K or anti D to eliminate those pesky (expected) discrepancies between different methodologies and required corrective action.     

[Eagle Eye 203]

Same here. I run one Positive and one negative for all tests.

[TMGal 4]

For your A-ive donor with the screen positive in gel and negative in tube, is there a pattern in the antigram? Gel is much more sensitive to Rh antibodies than tube. You said the patient is male so unlikely they received RhIg. If results repeat in gel, I would suggest Rh phenotyping the donor for c, e status.