How much is enough to change antibody screen from Positive to Negative

[jcdayaz]

I think "POOR IONIC STRENGTH SOLUTION" would have been very applicable and appropriate!! hahaha!

[bb4me]

Oh, we just call it normal saline. Thanks for the clarification. I must confess , I don't have any idea what "abnormal" saline might be. Why do we have the need to classify it as "normal"? Any thoughts on this?

Thinking back (WAY back) to school daze, i seem to recall that "normal" was the term used for saline that was isotonic with normal patient plasma (0.85% w/v, I think). Another term is physiologic saline. Anyone else remember this?

[Malcolm Needs ☆]

Oh, we just call it normal saline. Thanks for the clarification. I must confess , I don't have any idea what "abnormal" saline might be. Why do we have the need to classify it as "normal"? Any thoughts on this?

Thinking back (WAY back) to school daze, i seem to recall that "normal" was the term used for saline that was isotonic with normal patient plasma (0.85% w/v, I think). Another term is physiologic saline. Anyone else remember this?

Yes, I certainly do (which just goes to prove a dinosaur never forgets, let alone an elephant)!!!!!!!

:D:D:D:D

[RR1]

I remember the day we switched over from NISS to LISS testing and thought this was the most wonderful thing that ever happened to transfusion labs.

[L106]

The day we switched from 30 minute incubation with 22% Albumin to 10 minute incubation with LISS made my history book!! (Except you could no longer throw a crossmatch in and go to lunch and then stroll through the hospital gift shop while the testing incubated!)

[csjuarez]

We do not change a positive screen result to negative. If the screen is positive, we perform an antibody ID. If the presence of alloantibodies to common red cell antigens is ruled out, with or without additional positive cells, we report the antibody ID as inconclusive and perform coombs crossmatches. In the future if the antibody screen is negative then computer (or immediate spin) crossmatches can be performed since a clinically significant antibody was not identified.

Sometimes the more testing you do, the more confusing it is! Every testing system has it's strong and weak points, but who can afford the time and expense to attempt multiple procedures? Outside of a reference lab it is often times difficult to identify such a low incidence or weak antibody, and even then crossmatch compatible units are the best you can do.

I'm also one of those who vote "NO" on the use of microscope under most circumstances for antibody ID. Though gel is our primary method, LISS is occasionally used for special circumstances and I strongly discourage routinely examining these tubes under the microscope. We do use it when macroscopic resutls are questionable, as well as for DATs and FMH screens, though.

[conwaysbb]

Did I miss something somewhere that actually gave the specificity of the antibody? Did you then do an eluate on the positive DAT to see if it was also positive with the original screening cell?

The antibody identified was a clear cut microscopic anti-E which was further enhanced by PeG. In addition an eluate was performed and anti-E was identified. The Pathologist interpreted this as a serological event rather than a hemolytic event.

I believe what I will be doing will be requiring a antibody ID be performed and if negative a repeat of the antibody screen using the same screening cells but with PeG as the potentiator/additive. Of course a consultation with a senior tech or myself would be required to change the final result. This would all be documented in the patient's record with the information that results have been changed and the name of the nurse or MD that had been notified included in a blood bank comment.

In addition, we always use something like this as a training tool or continuing education event. It is always valuable to observe how the individual shakes out the tube, as the interpretation of gentle shaking means different things for different individuals :-). It was observed that the individual continued to shake the tube between the initial observation of tube in the agglutination viewer and the observation under the microscope. :-(.

Again, I am awaiting approval for automation so that variations in technique will not come into play and according to all the different manufacturers of automation, sensitivity will also be increased by using their products. My entire staff is looking forward to this.

Edited February 23, 2010 by conwaysbb

[cplatt36]

I must say that when I came to my facility people would clank the tubes against the convex viewing mirror and then shake the tubes to read the agglutination! Talk about a nightmare. I personnally have found viewing scratchy results microscopically very helpful in AS and ID. But good thing I finally got gel testing into my facility.

[cindym]

We switched to gel two years ago. We have the occassional patient who's antibody screen in gel is positive. The gel panel will have weak reactions (+1) on all panel cells. The tech will repeat the antibody screen in tube using LISS and it is negative. I do not feel comfortable changing the antibody screen results to negative because then they would quality for an immediate spin crossmatch. If anyone else is seeing this senerio, how are you reporting out the antibody screen results?

[Malcolm Needs ☆]

We switched to gel two years ago. We have the occassional patient who's antibody screen in gel is positive. The gel panel will have weak reactions (+1) on all panel cells. The tech will repeat the antibody screen in tube using LISS and it is negative. I do not feel comfortable changing the antibody screen results to negative because then they would quality for an immediate spin crossmatch. If anyone else is seeing this senerio, how are you reporting out the antibody screen results?

We see it all the time in my Reference Laboratory, and we report it is no clinically significant antibodies detected by LISS tube IAT at 37oC, but always mention the gel results in the report.

The antibody(ies) causing these gel only reactions have never yet been implicated in any sequelae whatsoever that could, even remotely, be called clinically significant.

As I have said in other posts, in the days before we had gel (and LISS come to that) we didn't kill our patients en masse!!!!!!!!!!!!!!

;)

[Shadya]

posted in error