Invalid ABO/D results on automation

[RR1]

I'm really interested in finding out the failure rate of your automation to interpret ABO/D types. It would be very helpful to know the approx % failures you are experiencing.

The equipment I am most interested in are:

Provue/ Diamed (Gel cards)

Galileo -microplate grouping

ECHO microplate strips

Ortho Autovue (Cards- glass beads)

Many thanks!

Edited February 27, 2010 by RR1
forgot to add a poll- never mind!

[carolyn swickard]

We are seeing very few failures for ABORh on our ECHO. One thing we do notice, backtyping is frequently weaker on the ECHO than it would be in tubes, but even 1+ positives will interpret correctly. We occasionally see very small agglutinates in A or B backtyping wells that should be neagitve - the ECHO will fail these interpretations. I wonder if it is a cold or rouleaux that causes these or micro clots in the EDTA specimen? Overall, we are happy with the job being done on the ECHO.

[L106]

We are experiencing exactly the same things as cswickard.

[RR1]

Thanks- I am currently extracting these figures from my Galileo & ECHO, but similar observations with the reverse group being seen. Our immucor specialist said we should possibly be centrifuging our EDTA samples for 10mins prior to testing- is this what everyone else is doing?

[L106]

We centrifuge our patient specimens for 5 minutes. (If we centrifuged them for 10 minutes our manual tube technique testing would be faster than the Echo!) Personally, I doubt that this is the solution to the problem.

Donna

[adiescast]

We definitely have problems with the Galileo missing D positive patients. We centrifuge our samples for 5 minutes, which was what Immucor recommended to us. I doubt the centrifugation time affects the D typing. I have not done an audit to determine how many get missed. I changed our policy to require that a second type be done manually for any patient who is Rh negative on the Galileo and has no history here.

[kate murphy]

Results on automation may not always match manual tube testing for several reasons. Sensitivity of direct hemagglutination used on the Galileo & Echo for ABO/Rh is 1+ or better - a very weak reaction will be called negative. Some of our techs would call some of these reactions 2+.

Different anti-D reagents are used on automation than bench - anti-D's are now all monoclonal, but each reagent is specific for a different epitope of the D antigen. We are seeing many more weak D and partial Ds than previous reagents (human origin pools). I think there is much more variation in the D antigen than we thought.

The big question is what do you want call your patients - D pos or D neg? Think carefully, if you have an OB/Gyn population, it's important to ensure that D partials are called D neg to qualify for RhIG. There are no serologic reagents that will tell you this definitively. So study your reagent reactions, do some on-line research and pick an anti-D that is negative with most D partials. We are in process of changing manual tube reagent to match reagents used on our Galileo specifically for this purpose.

Bottom line, many of us now have 2 methodologies in our labs. We are bound to see variations in results. Just as Chemistry lab what they see between methods!