Re-testing antibody screens

[Malcolm Needs ☆]

Not when I'm on-call (as I am tonight).

I'll just say "No" (purely for the sake of the patient, of course)!

By the way, I've sent you that Powerpoint on serological techniques, Rashmi (work email). Hope it's what you want and is of use.

[Eagle Eye]

We have ProVUe and manual gel...if the reaction on ProVUe is questionable we repeat screening by manual gel. Or If we get a negative panel we repeat screening by manaul gel.

[RR1]

Hi aakupaku, its good that you check your results. No technique is infallible, as long as we can explain why a previous antibody is no longer detectable (possibly due to a recent transfusion of antigen negative blood), then re-screening is not always necessary.

However, I like to think of patients that have known antibodies as being an additional, random 'positive control'. If these are not detected when they should be- then the full process- whether automation or manual, needs to be checked thoroughly.

[RR1]

Now this poll is closed - it's good to know that approx 60% users either re-test discrepant screens each time, or at least selectively. After all the problems I have encountered with my automation (and heard from users of different equipment), I personally feel these should be investigated properly.

For the 40% users who would never question or re-test a screening discrepancy, I would like to ask what steps would you normally take if your routine screening controls failed?

Many thanks!

[Judy hedglin]

Do not repeat due to possibility of titer issues--give antigen neg blood for previous ab.

[RR1]

Do not repeat due to possibility of titer issues--give antigen neg blood for previous ab.

Hi Judy, have you considered that the antibody may not have been detected due to analyser problem and not deterioration of the antibody itself?

I know we would always give antigen negative blood to these patients so there would be little risk, but how about the ones we don't know have antibodies and we fail to detect these?

During a recent EQA exercise one hospital UK missed an antibody (by automated gel) due to a camera misalignment. This can happen with any automation used.

[eric1980]

My lab do not repeat screening for negative results for patients with known antibodies from the distant past. We will continue to take the past anitbodies into account and issue antigen-negative blood just in case of stimulating a secondary immune response.

But if the recent screening is strongly positive and the current one is negative, then common sense warrants that we have to repeat or ask for a new specimen.

[RR1]

Hi eric,

You seem to be doing the right thing. How many analysers does your lab have, and if >1, do you test some positive antibody samples between them, to show they are giving comparative results?

[eric1980]

Rashmi: My lab do not have any analyser... We brought in a Ortho Autovue very early this year, finished evaluation, but haven't started using it yet. This is due to data transmission conflicts between Ortho and Mediware (we are using HCLL). -_-"

So we are eyeballing our Diamed gel cards and reading it under light... =/ It's like stone age technology as compared with you guys using analysers, but at least the reliability is there... (may not be worth the work considering the volume... we get ~100 specimens per day).

[RR1]

Thanks eric, once you get the data transmission sorted you'll wonder how you ever coped without an analyser.