Weakly positive antibody screen, what next?

[kirkaw]

We use GEL technology for routine antibody detection. Our policy is not really clear on what to do when you have a positive antibody screen. I would prefer to have my staff do a panel in GEL but my predecessor allowed them to do tube screens.

Also, suppose we do the antibody panel in GEL and it is negative. Again, my staff is used to doing a tube screen. Is that necessary? In the past, when the GEL panel and tube screen are negative, they do immediate spin crossmatches. I'm not sure I'm comfortable with doing immediate spin crossmatches following a positive antibody screen, regardless of method. Comments?

Thanks, Amelia

[David Saikin]

If you use gel for your screen why would you use a less sensitive method for an ID? The only time I stop using gel is if I have an warm auto - I cannot absorb out all the ab and use gel. I do my warm autos in tubes with PeG (and Peg autoabsorptions).

[kirkaw]

Thank you David. I agree. I was just trying to make sure that I wasn't being overly cautious because I am new to the supervisory role. I am trying to catch on new methods, technology and philosophies.

[Malcolm Needs ☆]

I agree with David that, if the screen is positive by gel, do the an ationtibody investigation in gel.

If, however, the antibody shows no definitive specificity, or is too weak for conclusive identification, with the possible exception of Kidd antibodies, I would be quite happy to give cross-match compatible blood (cross-matched by gel), on the grounds that the antibody is too weak to be clinically significant, and, at best (worst?), would only cause the transfused red cells to be cleared slowly, and not last as long in the patient's circulation as could be expected.

The bonus is, of course, if the antibody is then stimulated to become stronger, it will be easier to identify next time. This may sound brutal, or even unethical, but it was something that was propergated by Shiela Worrlledge years ago - and she had a hand in training one George Garratty - and he isn't a bad serologist!!!!!!!!!!!!!!!!!!!!!!

[Deny Morlino]

This may sound brutal, or even unethical, but it was something that was propergated by Shiela Worrlledge years ago - and she had a hand in training one George Garratty - and he isn't a bad serologist!!!!!!!!!!!!!!!!!!!!!!

Malcolm you are the master of understating lol!!

[JEMarti]

To be fair many people do a panel in a media that does not render itself easily to doing a panel. Solid state assays are one instance where many labs will follow up a positive screen with a PEG panel. It isn't ideal but that is reality. Best case is you do the panel in Gel. Second best is in PEG.

And I will agree with Malcom's comment. Years ago I had a Technical Director who advocated giving crossmatch compatible and if they reacted then next time we would know what it was. It isn't unethical, we simply need to understand the limits of our ability, our technology and our knowledge. If I have a clean crossmatch then I have done the best I can with what I have been given.

[L106]

We use GEL technology for routine antibody detection. Our policy is not really clear on what to do when you have a positive antibody screen. I would prefer to have my staff do a panel in GEL but my predecessor allowed them to do tube screens.

We were starting to see a similar problem.......When the antibody screen was positive by our routine method, different techs were starting to use different testing techniques and methods to investigate/work-up the problem. (And as David Sakin discussed, sometimes they were going to less sensitive techniques, which doesn't make sense.)

You might consider writing a flow-chart of what to do when the GEL Antibody Screen is Positive. Sit down & think about what testing you would like your staff to do (and in what order, etc.) Then you can present the flow-chart to your staff as the "routine recommended work-up when the GEL Antibody Screen is Positive." (You should probably add that in certain situations when you have an antibody history on the patient, it may sometimes be appropriate to not follow the routine flow-chart.)

Some of my staff were very appreciative and mentioned that they were "visual" learners, and that looking at the flow-chart made things much more "logical" for them than verbal explanations of what should be done.

Donna

[Mabel Adams]

We have a certain amount of trouble with "gel junk", questionable reactions althugh that is better since Ortho instructed us to keep the cells in the dark and refrigerate them more. We sometimes follow up with a PEG screen which I have found to be more similar in sensitivity to gel than any other tube method although that depends on the antibody. What I prefer is that a gel panel be performed but, if that is also equivocal or looks like junk then a PEG screen may be performed as a substitute and the screen turned out as negative. PEG is certainly an acceptable testing method. Antibodies to the gel diluent are more common than similar reactions in tube testing. When I came here they were used to doing saline screens for weak questionable reactions in gel, so I at least got us ramped up to using PEG. I doubt that anyone is using a less sensitive technique for IDs when they think it is a "real" antibody.

[LCoronado]

If the gel screen is positive, we do a gel panel. If the panel is negative, we open a new set of gel screening cells (if available) to rule out those pesky false positives (mable's "gel junk") that sometimes occur even when we are careful about refrigerating the cells and protecting them from light. Most of the time the screen is negative with the new cells. Because we are a small hospital and don't use up the screening cells that quickly, we have started discarding them after they have been open for about 10 days, which has saved us many headaches and "wild goose chases".

On the other hand, weak nonspecific reactions that appear in both the gel screen and panel may be due to a cold agglutinin or reactions with the diluent. We would investigate further by performing a cold panel and a tube screen; we then report a cold agglutinin if it is present. If the reactions do not support a specific identification, we report "none identified" or "all significant antibodies ruled out". At the least, this gives the person who next works up this patient a heads up that something was seen, though nothing was identified.

For the crossmatch, we always start with gel. If necessary, we perform a tube crossmatch but always include an AHG phase for these patients.

We have found flow-charts to be helpful for the most part, but at times our cross-trained generalists seem to depend on them a little too heavily, choosing to use little or no grey matter of their own when conducting an investigation.:tongue:

Edited May 10, 2012 by LCoronado

[Likewine99]

We've found that if you get a "funny looking, sort of hazy" screen in gel to check for rouleaux using the old saline replacement technique before you head off into panel land.

I agree with the other posters, if you do the absc in gel to do the panel in gel too. In this instance with a pos scr and neg panel you could revert to a tube screen just to confirm that it's not gel junk. We also use "all common clinically significant antibodies ruled out" when we've ruled out everything. These pts get a gel xm with an immediate spin added to satisfy the CAP reg for ABO compatibility.

[mollyredone]

What Amelia said in her original post was that if the gel screen was positive the techs wanted to do a tube SCREEN, a tube panel and she would like them to do a gel panel. I am in the process of trying to make a flow chart as well, so everyone is on the same procedural page with new patients. I agree that even if the tube screen (which I would do if the gel screen and panel were junky) is negative, I would not be comfortable with IS XM and would do gel XM.