Missed Kells on Echo

[RR1]

Hi Linda,

We went from tube to Gel and now to solid phase- which is why we may be experiencing problems. All I can say is I am very fond of my Galileo and ECHO analysers- as automation they are very impressive compared to rival technology and the software is excellent. One of my main concerns is still with solid phase serology itself.

Rashmi

[krichards]

We have been using our Echos for close to a year now. We identify an average of 4-6 Kells each month...some id'd when we were still using gel, and many that were not. Like others have commented, we have discovered antibodies not detected by gel: Jka, C,and E. Yes, gel sometimes catches something that the capture does not. However, we feel that we are detecting many more antibodies with capture than we are missing, and that those we are missing are most likely IgM.

[RR1]

We all seem to be having totally different experiences with this system- I don't see a similar debate to this level with other methodologies used.

Also if anyone could answer my original question: 'what is it about capture that makes it more specific than Gel systems to not detecting IgM antibodies and also being specific to only certain antibody subclasses'- would be really appreciated.

Thanks

[marilynm]

I have not had time to digest all the postings on this topic since I was last on, but one point I can comment on, is that Capture (Solid Phase) Echo uses indicator cells that are made using a monoclonal Anti-IgG (16H8) that detects all IgG subclass antibodies that are clinically significant; ie, IgG 1, IgG 2 and IgG 3. The only IgG subclass antibodies not detected are IgG 4 are NOT clinically significant.

On gel, I understand that IgM antibodies show up in gel if they are strong and cells/agglutinates get trapped in the top of the gel as the agglutinates can form as the serum and test cells are added, even before incubation, or it happens when centrifugation occurs and the temperature cools down.

Lastly, Rashmi, have you sent any of your sample of anti-K to the manufacturer of the Echo? I believe it is always best to give the manufacturers, no matter who they are, a chance to test a sample that gives unusual results.

Is this anti-K IgM? Have you done 2 ME or DTT-treatment of the serum/plasma to see if it does indeed have an IgG componcent? maybe I missed where you said this.

My philosphy is that the antibodies are what are unusual and the FDA licensed reagents/products/instruments (especially in the US) are very good or FDA would not have licensed them.

We are currently doing a study of three techniques (Tube, Gel and Solid Phase) and I can tell you right now that there are examples of anti-K, anti-E, etc that are detected by one technique and not the other two. It will be fun to see what our final results turn up.

There is NO perfect technique.

I rattled on. Have a good weekend everyone.

Marilyn Moulds

[marilynm]

Dear Jeff: I just noticed on my posting of last week that I had answered Rashim's questions but that I had asked him instead of you whether you sent your anti-K to the manufacturer of the Echo?

Also, I just remembered another fact about anti-K, and I will have to find the reference for this too, but in the literature there are different examples of anti-K that do not react well or not at all in some types of LISS. Perhaps your antibody is nonreactive in solid phase, not because of the instrument, but because of the LISS addative that is used.

I know that the cells used in gel are suspended in a LISS solution, but the formulation is different from the solid phase LISS.

Maybe you could try and experiment and leave out the LISS in the solid phase testing and see what happens.

Just another suggestion.

Marilyn M

[RR1]

Hi Marilyn,

I have had a couple of anti-K incidents, one was found to be an IgG 4. The other anti-K (known patient) was initially not detected by solid phase, but when repeated on same sample by solid phase gave a 1+- 2+ reaction. I have also had other antibodies:Anti-Fya, anti-S, anti-E reacting similarly. These antibodies all came up as expected with Gel and tube IAT.

Some of the samples were sent to the manufacturer. I now currently send any problems directly to the reference laboratories to perform sub-classes and follow ups.

It is the repeatability aspect that I am worried about. I would not be happy to transfuse any of these patients with the designated antigen positive blood regardless of the determined IgG subclass. What about amanastic responses ?

10 years ago it was accepted that we would miss some antibodies that were not detectable by the tube technique and we would see a number of delayed transfusion reactions each year.

When we changed over to gel techniques the number of DTRs was significantly reduced- how can it be acceptable to miss detecting - what I would consider to be clinically significant antibodies, that would have been detected 10 yrs ago...... and accept that there may be a rise in DTRs ?

What do blood bank staff consider to be an acceptable number of reactions? 1:3000, 1:6000, 1:12000 ...i'm still trying to figure this out. It's all about reducing risk and improving patient treatment and care- this is our moral and professional responsibility.

There must always continue to be improvements in the service we provide, we cannot just accept that a change of any technique will have increased associated risks......we need to question what we are seeing, we also need to listen to our staff when they express concerns. Decisions should also be based on our own experiences over the years.

There are papers on method comparisons (especially solid phase Vs tube)- that have interesting results- similar to the repeatability problems that I am experiencing. May be we could discuss these once you have completed your evaluations.

The whole aspect of these problems needs to be discussed fairly, - i'm prepared to be found 'wrong' in my conclusions......the main point being that these discussions are open and everyone reports problems they find with ANY technique.....without the threat of litigation, without confidentiality clauses and constraints placed on staff evaluating systems, by manufacturers. .........its all about patient safety .

Thank you for your feedback.....its really appreciated.

Best WishesRashmi

[RR1]

Further to this thread- it would be good to hear back from folk as to any further progress made with their antibody screens. As I have posted on various other threads one possible cause of my 'failure to detect' some of our missed antibodies could have been due to incorrectly stored phosphate buffered saline for the wash phase. This did not however account for a missed anti-Fya, that was detected by Gel and Tube and also could notbe detected by another user (that stored their PBS correctly!!).

Do labs buy in their wash PBS or produce this in-house?

Thanks

[macarton]

In our validations, we've had 2 Kells, 2 Duffy a, and E weakly positve in gel and negative with the Echo. Mary

[RR1]

Hi Mary,

If you have further samples you could try and see if these antibodies are detectable by Tube IAT. Also try repeat testing on the ECHO to see if reactions are consistantly negative. I have had similar findings and because I also have an ECHO and Galileo - there are consistancy problems between the two analysers as well. One may detect an antibody whereas the other one may not.

This issue may be resolved by converting the Galileo to next software upgrade that allows the same 3 cell screen to be used.

How did you explain these discrepancies in your validation?

many thanks.

[macarton]

We have submitted testing results to Immucor for analysis. We have not gone live.

[RR1]

Thanks Mary-you may get one of the following responses:- that these are IgM or IgG subclass IV antibodies, 'we have never seen this problem before- must be a one-off', the lab have not handled strips correctly, 'not all techniques detect all antibodies' 'the analyser needs adjusting' etc..

It can also be quite difficult to follow up some of these discrepancies due to limited availability of patient samples.

Would your previous technique have missed all of these antibodies....probably not.

Would the 'gold standard' Tube IAT have missed the antibodies?

Just remember to carry on repeat testing any discrepancies...until you are totally happy with the system. Question the control well used on the 3 cell screen....this only controls the wash phase, as this is a pre- bound sensitised cell.

Good luck!!