Interpreting ECHO "negative" results

[Karrieb61]

HI all, I had the opportunity the other day to look at another lab's Immucor ECHO and the Supervisor showed me a few results on the screen that were negative but not quite negative (loose cells around the bullseye or at least that's what they looked like) . She said that those types of not-completely-clean negative results are investigated as being weakly positive for antibodies etc.

I am hoping that an ECHO user can give me an opinion on how often this happens. As I move our techs away from the microscope, it will be important for them to feel confident interpreting ECHO results and I would hate to see people panic and start doing back up tube/micro readings of "negative but not quite" reactions from the ECHO. I think that when I quiz the Immucor Tech Specialist, I may be told to not over-read these.

Opinions anyone? Thanks

[Sophie1210]

We get a few equivocals (question marks) every month called by the Echo. If the Echo calls the screen negative then we call it negative. If it gives us a question mark then we take it to the bench for a tube screen using PEG. 

[carolyn swickard]

Given the extreme sensitivity of the ECHO screens - we call them negative if the instrument calls them negative.  Only very rarely now do we see one the instrument calls negative that visually looks "somewhat positive", especially since Immucor has their Solid Phase problems fixed again.  Any samples that we have any questions on, we also take to PEG in tubes - not much other choice.  If you are used to Solid Phase manual testing, you will think the ECHO looks a little "hazy" around the dots, but that just seems to be the nature of the test on this platform.  We have been using an ECHO for 5 years now and are doing very well with it.  Antibody panels on the ECHO are the only way to even replicate some of these weak positives if you want to have some idea of what the instrument is trying to detect.  Tube testing and manual solid phase testing just don't show them.  Most of the time they are just some non-specific "junk" and the only thing you can do is coombs crossmatch units for the pt.  That may sound like too little work, but understand, the ECHO is probably the most sensitive platform out there and it will find stuff at the very edge of detectability.  Good luck.

[AMcCord]

We also see a few iffy reactions a month - some with question marks, some marked negative by the instrument but still iffy looking. We look at the well - if the button is ragged with tiny tendrils or the background is freckly with a distinct halo we do tube/PeG testing. If the button is solid looking with a pretty smooth edge, even if it has a little smudginess/color bleed appearance, we call it negative. (Don't you love my technical terminology .) It is important not to over-read. Yes, there will be some over-reading at first, but the more results that you see, the more comfortable you will get interpreting the questionable ones. Most of my techs were quite comfortable with these types of reactions within 3-6 months - or less - of use (and we are a smaller facility that has what I would call an average test volume). We've been using the Echo for 6+ years and still like it.

[Karrieb61]

Thanks to all of you for your comments and suggestions! They are all very much appreciated! Keep 'em comin"

[Malcolm Needs ☆]

Given the extreme sensitivity of the ECHO screens - we call them negative if the instrument calls them negative.  Only very rarely now do we see one the instrument calls negative that visually looks "somewhat positive", especially since Immucor has their Solid Phase problems fixed again.  Any samples that we have any questions on, we also take to PEG in tubes - not much other choice.  If you are used to Solid Phase manual testing, you will think the ECHO looks a little "hazy" around the dots, but that just seems to be the nature of the test on this platform.  We have been using an ECHO for 5 years now and are doing very well with it.  Antibody panels on the ECHO are the only way to even replicate some of these weak positives if you want to have some idea of what the instrument is trying to detect.  Tube testing and manual solid phase testing just don't show them.  Most of the time they are just some non-specific "junk" and the only thing you can do is coombs crossmatch units for the pt.  That may sound like too little work, but understand, the ECHO is probably the most sensitive platform out there and it will find stuff at the very edge of detectability.  Good luck.

Yes, we get an awful lot of non-specific junk and, frankly, negatives sent in by our ECHO users.

Even if the antibody has an real specificity, I question whether or not the antibody is clinically significant (with the POSSIBLE exception of Kidd antibodies).

The ECHO is certainly sensitive; I wouldn't argue with that. I often wonder if it is too sensitive though?

[Karrieb61]

Thanks Malcolm. I'm not sure what you mean by "send in by our ECHO users" but I'm still new to Pathlabtalk

[estiner]

We have had our ECHO for 4yrs now and we love it.  Yes, there are some reactions that the instrument calls "?".  If it appears to be negative visually, we check the reading for the strength of the reaction (Highlight the specimen<Right click<Result file<then scroll down to REACTIONS)  The Assay cutoffs are on page D-6 of the ECHO manual.  It helps us decide how strong the instrument feels the reaction is.  Then if we question, we go to PeG as our backup.  If we get positive screen, then negative or inconclusive panel, we repeat screen in PeG.  If negative, then we crossmatch on the ECHO and if compatible, consider our reactions due to capture technology.  Otherwise we address whatever specificity is determined.  You must keep in mind that some antibodies react stronger on the ECHO while others react better in PeG.  That is why it is good to have two different methodologies available.

[Malcolm Needs ☆]

Thanks Malcolm. I'm not sure what you mean by "send in by our ECHO users" but I'm still new to Pathlabtalk

Hi Karrieb61,

I am the manager of a Reference Laboratory, so all of our samples are sent in by our hospitals.

[David Saikin]

I have wondered for the past 4-5 yrs whether solid phase and gel are too sensitive. Even with gel there are those "iffy", weak, junky looking reactions. My curiosity wants to ask how many of the iffy gel/solid phase results translate into any reactivity with PeG (specific or not)? Anybody . . .

[EDibble]

I totally agree with cswickard

Given the extreme sensitivity of the ECHO screens - we call them negative if the instrument calls them negative.  Only very rarely now do we see one the instrument calls negative that visually looks "somewhat positive", especially since Immucor has their Solid Phase problems fixed again.  Any samples that we have any questions on, we also take to PEG in tubes - not much other choice.  If you are used to Solid Phase manual testing, you will think the ECHO looks a little "hazy" around the dots, but that just seems to be the nature of the test on this platform.  We have been using an ECHO for 5 years now and are doing very well with it.  Antibody panels on the ECHO are the only way to even replicate some of these weak positives if you want to have some idea of what the instrument is trying to detect.  Tube testing and manual solid phase testing just don't show them.  Most of the time they are just some non-specific "junk" and the only thing you can do is coombs crossmatch units for the pt.  That may sound like too little work, but understand, the ECHO is probably the most sensitive platform out there and it will find stuff at the very edge of detectability.  Good luck.

[EDibble]

To answer David's last question, in my experience, solid phase on the ECHO is more sensitive then PEG (which happens to be our backup method.) We have had ?? reactions on an antibody screening that were stronger on a capture panel, and ended up being a real, significant antibody.

 

No matter what method you use, there will always be those patients whose specimens give a false positive. We just have to use our brains like we were taught oh so long ago.    

 

Beth

[Sophie1210]

If we get question marks on the Echo and negative in tube, we'll call it negative. However, if we get a positive on the Echo that doesn't work out on the panel and negative with PEG we result a positive screen and put in a comment that it was negative in tube and no clinically significant antibodies were found. We also result an Unidentified anybody to get a hard stop so that patient can't ever get an electronic crossmatch (if at a later date the screen is negative, then our system would allow one if there were no antibody in there).

 

We had a patient where this occurred and there was no clear cut answer on the panel and everything significant was ruled out. 2 weeks later the patient had a clear cut anti-C. Looking back the only cells that reacted were C+, just not enough and not in the correct pattern to identify. Yes, the Echo is overly sensitive but sometimes it picks things up before anything else.

[AMcCord]

I have wondered for the past 4-5 yrs whether solid phase and gel are too sensitive. Even with gel there are those "iffy", weak, junky looking reactions. My curiosity wants to ask how many of the iffy gel/solid phase results translate into any reactivity with PeG (specific or not)? Anybody . . .

There were some intruiging posters at AABB related to iffy solid phase reactivity. Several of the posters were showing that as many as 1/3 of their patients had identifiable antibodies at the next or later visit. If I recall correctly, most of those iffy antibodies were not showing up/identifiable with tube testing. It will be interesting to see where that goes over the next few years.

[Karrieb61]

Thanks again everyone, this is a wonderful site and I'm lovin' the helpful info!

[Eagle Eye]

Echo users, how do you run your full crossmatch?

[AMcCord]

Echo users, how do you run your full crossmatch?

 

Currently I'm doing tube IS and AHG w/ PeG. I would like to switch to tube IS and doing the AHG on the ECHO, just need to get our new medical director to OK the switch.

 

Immucor particularly recommends doing the AHG on the ECHO for those specimens with 'antibodies' without specificity. The rationale is that if there is a 'real' antibody forming but not yet identifiable and your tube testing is coming up negative because of lower sensitivity, doing the crossmatch on ECHO would detect 'antigen positive' units more reliably. The downside will be the warm autos that pop up on ECHO because of the increased sensitivity. Those would still have to be done by tube, but for us that wouldn't be a large burden most of the time.  

[Karrieb61]

Thanks again everyone, my learning curve is helped by these thoughtful comments. ECHO should be arriving on our doorsteps in about a month, wish us luck!

[goodchild]

I have wondered for the past 4-5 yrs whether solid phase and gel are too sensitive. Even with gel there are those "iffy", weak, junky looking reactions. My curiosity wants to ask how many of the iffy gel/solid phase results translate into any reactivity with PeG (specific or not)? Anybody . . .

 

There are definitely times that "?" reactions on the Ortho ProVue antibody screen with negative manual panels translate into antibody specificities identifiable in PEG. Off the top of my head we've seen this happen with anti-E, -K, -Jk(a), -M, -Le(a) and -Le(. Now, do I have the numbers for times that we've done it and seen nothing compared to the times we've found something? No and I wish I had a way of capturing that information.

[mcgouc]

For the question marks on the ECHO, we do as estiner does and check the number associated with the strength of the reaction.  A lot of times when we have question marks on the screens, we have question marks on the panel which makes ruling out clinically significant antibodies difficult.  I have been told by Immucor that if the questionable reactions have what appear to be a pie slice shape missing, it is probably the instrument.   We perform the AHG crossmatches on the ECHO and we routinely get the units compatible when we are getting these "?" reactions in the screens and panel.  While we are doing the panel, we perform a gel screen and that is usually negative.  Since using the ECHO, I think we find more antibodies to low incidence antigens on the panels in addition to the antibody that caused the screen to be positive.  

[Karrieb61]

Oh boy, so much left to learn, thanks again everyone and comments are still very much appreciated!

[Maureen]

Our lab has used the Echo for 5 years.  Immucor Technical Communication cc-09-042-02 (Nov 2009) recommends 'you perform a visual verification of negative reactions before final release...' due to false negative interpretations. 

There is nothing (I can find) in the manufacturer's package insert or Operator's Manual which requires this step.

We still follow this recommendation, as we find instances where the interpretation is a false negative.

Our experience shows these may or may not be resolved as a clinically significant antibody. 

An Echo panel is usually run, or PEG screen/selected cells.

We do full crossmatches on the Echo.

 

This is sometimes quite a bit of work to identify something unimportant, but in other cases we clearly id anti-E, anti-Jka or b or others prior to transfusing.

[Karrieb61]

OK, thanks Maureen!

[rebeccarjthomas]

Quite a few of our customers use the ECHO. At times they report positive reactions, sometimes strong, that we cannot duplicate using manual Solid Phase. My understanding is that: On the ECHO - pt. sample is added prior to LISS. Manual Soloid Phase - LISS is added prior to patient sample. Has anyone looked at this difference specifically? I don't think I've seen anything published on manual versus ECHO Solid Phase testing. Thanks, Becky

[AMcCord]

Becky.......that's an interesting thought. I don't do manual solid phase, but would like to - this might be a good reason to push forward with that project.