We have an obstetric patient (3rd  pregnancy) who is group O ccdee who has an antibody which shows anti-D specificity however this antibody is only very weakly reactive by IAT and enzyme.Sometimes it is reactive by bothIAT  and enzyme however unusually it sometimes reactive by IAT only . This antibody was also present in her second pregnancy. There has been no known administration of anti-D prophylaxis in her current pregnancy. I would be interested to hear your thoughts on this.

Are you using a one-step or a two-step enzyme technique?

The test is performed on the IH1000 using a papainised panel and neutral cards.

So how strong is the reaction in Coombs?

1 hour ago, galvania said:

So how strong is the reaction in Coombs?

Coombs????????  Anna!!!!!!!!

Am I to understand that the enzyme test is NOT an antiglobulin test ? Am i correct in thinking that's what "neutral cards " mean ? If that is the case, you are not comparing like assays. One has an antiglobulin reagent, the other does not. Use of enzyme-treated cells may enhance detection of anti-D before the antiglobulin phase, but not always.

My interpretation of your results is that you have a weak IgG anti-D, only reliably detected by IAT.

Yes ,the neutral cards do not contain any anti globulin reagents however I thought that if an Rh antibody was present this would be enhanced by the enzyme techniques? The current  BCSH guidelines for compatibility testing  state that is acceptable to exclude Rh antibodies using validated techniques with enzyme treated cells. That being said, if an antibody was detected by IAT showing Rh specificity I would not exclude its presence even  if it was negative by enzyme technique.

In this case the reactions were variable but never more than a 2+ reaction, sometimes there in both techniques , and sometimes only by IAT. In the most recent sample, the enzyme is negative and the only reactions by IAT were with an R2R2 in the screening cells and with the R2R2 in the panel. (both 1+ reactions). 

It is also possible that she has had a prophylactic anti-D injection that has not been documented in her notes. As far as management of the pregnancy is concerned anti-D prophylaxis will be recommended at present.

 

 

Has she had any IVIgG for any reason (recently I mean)?

I don't know for sure but there was nothing on her referral suggesting she had received treatment for any medical conditions. 

Thanks for the rapid answer.

I am away for the next couple of days, but will keep thinking!

Thanks. Much appreciated! 

It seems a weak anti-D which is sometimes too weak to show up on enzyme technique. Maybe the former several  pregnancies immune the lady.Maybe knowing the kids D type will help.

I don't suppose there is any possibility of seeing the images in the gel cards is there?

22 hours ago, Malcolm Needs said:

Coombs????????  Anna!!!!!!!!

Sorry Malcolm.  Mea Culpa.  Can I plead old age and being very tired?

15 hours ago, catm said:

The current  BCSH guidelines for compatibility testing state that is acceptable to exclude Rh antibodies using validated techniques with enzyme treated cells.

In this case the reactions were variable but never more than a 2+ reaction, sometimes there in both techniques , and sometimes only by IAT. In the most recent sample, the enzyme is negative and the only reactions by IAT were with an R2R2 in the screening cells and with the R2R2 in the panel. (both 1+ reactions). 

It is also possible that she has had a prophylactic anti-D injection that has not been documented in her notes. As far as management of the pregnancy is concerned anti-D prophylaxis will be recommended at present.

 

 

I am not familiar with the British regulations, but I imagine that said compatibility testing must include a technique to detect IgG antibodies. The enzyme test you describe may detect them but not always - exactly the situation you outline.

It still sounds like a weak anti-D. The variability in reactivity over time from sample to sample might just be because the patient is pregnant - their immune systems are doing very strange things, including exhibiting a fine-tuned tolerance for the "not-me / parasite" that they are carrying.

Can you do an antiglobulin test using enzyme-treated cells ? If you can, it would be wise to include an enzyme-treated autocontrol.

Yes Enzyme IAT will definitely help to solve the problem. Just wondering how about performing panel with known Anti-D to check quality control of panel cells. 

Did you send sample to reference lab for quantification? 

I think doing enz-IAT is missing the point here.  Usually one would expect an anti-D to react more strongly or at least AS strongly with papain-treated cells  (2-step) than with non-treated cells in an IAT.  Of course there are the odd exceptions and this is clearly one of them.  So, provided your weak anti-D control is working correctly with the papainised cells, then it has to be patient-related rather than instrument/reagent related.  I know it's a bit weird but I wonder if this anti-D is a mix of IgA and IgG and that sometimes the IgG component is not visible, and that the IgA part only reacts by IAT but not in papain.  Having said that , I don't KNOW that an IgA antibody would not react in pap.  I'm just surmising.  Malcolm, do you know whether IgA antibodies would react in pap?

1 hour ago, galvania said:

Malcolm, do you know whether IgA antibodies would react in pap?

Good question Anna.  From my point-of-view, I cannot see a reason why they should not.  IgA anti-D is certainly not unknown, but I wonder how these were detected, if it were not by the use of papain-treated red cells, as most antiglobulin reagents would not have a significant amount of anti-IgA in them.  Like you, I am surmising.

2 hours ago, galvania said:

I think doing enz-IAT is missing the point here.  Usually one would expect an anti-D to react more strongly or at least AS strongly with papain-treated cells  (2-step) than with non-treated cells in an IAT. 

I disagree. I would not expect enzyme-treated cells used in a direct agglutination test to react better than those same cells used in a technique using an antiglobulin reagent.

3 hours ago, exlimey said:

I disagree. I would not expect enzyme-treated cells used in a direct agglutination test to react better than those same cells used in a technique using an antiglobulin reagent.

Sorry, but I strongly agree with Anna.

19 hours ago, Malcolm Needs said:

Sorry, but I strongly agree with Anna.

Fair enough. Just to clarify......your (and Anna's opinion is that a 37C test using enzyme-treated cells and no antiglobulin phase will detect anti-D better than a test using the same enzyme-treated cells and an antiglobulin reagent ?

3 hours ago, exlimey said:

Fair enough. Just to clarify......your (and Anna's opinion is that a 37C test using enzyme-treated cells and no antiglobulin phase will detect anti-D better than a test using the same enzyme-treated cells and an antiglobulin reagent ?

No Sorry.  My fault I suspect.  In order of sensitivity for anti-D, I would go enzyme-treated-IAT, then enzyme-treated, then IAT with untreated red cells.

15 hours ago, Malcolm Needs said:

No Sorry.  My fault I suspect.  In order of sensitivity for anti-D, I would go enzyme-treated-IAT, then enzyme-treated, then IAT with untreated red cells.

That fits with my thinking, too. I suspected we were having "communication problems". Ain't the English language grand ?

26 minutes ago, exlimey said:

Ain't the English language grand ?

Ain't it just!

Just to update on the latest results for this patient. The most recent sample gave a 1+ reaction with the  R2R2 cell on the ID panel but was negative with the 2 R1R1 cells  cells by IAT and all direct enzyme cells. We also performed an enzyme IAT and got (+) reaction with the 2 R1R1 cells and a 1+ reaction with the  R2R2 cell. We are concluding that it is a weak anti-D and we will continue to monitor throughout her pregnancy. It has not yet been quantified in this pregnancy.