WhiteMB,

The introduction of an IgG Ab into the circulation is represented by an "S" curve plot of "Ab concentration in the plasma" (X axis) verses "Time" (Y axis). One of the unique characteristics of an "S" curve is that there is an initial "Lag Phase" (representing the start of the curve). This lag phase occurs here because when the IgG Ab makes it's initail appearance in the circulation it bonds to accessible Ag sites thereby taking the IgG out of the plasma and away from our detection capability in the BB. And we all know that when we collect a blood specimen this specimen represents a single snap shot of the circulating whole blood at the time of collection (just like a Polaroid). The DAT detects bound IgG only; the Auto Control "may" detect bound IgG and/or anything else bound to the RBC's. I worked at a facility that did not practice running Auto Controls with Panels; they said that they did not want to open a can of warms; my current employer wants to open that can of warms always. How often do we see a positive DAT and a negative Panel? Rarely in the hospital setting but maybe Malcolm sees it more often in the Reference lab (Lucky you Malcolm). But make no mistake that the positive DAT is very clinically significant and if I had the choice of which test to run in addition to the Panel I would chose the DAT because it can detect the "Lag Phase" were the Auto Control may not; and thereby give us a more complete picture of where along the immune response cycle this patient may be. In reality these are difficult choices indeed because there is a weighing of cost to patient benefit. I'm a bleeding heart, so I would always side with the patient benefit over cost. When we went to plastic flatwhere at some of our favorit eateries we will never go back do to cost structure. I always think it's better to structure cost around patient benefit solely or otherwise our work, and medical, advances are meaningless.

Sorry for the rag. I hope this helps a little.

My fellow posters,

I feel a need to expand on this post in order to further explain the "S" curve plot and how it relates to the testing that we perform. The next phase of the plot is the "Exponential Phase" wereby we see an exponential increase in the concentration of Ab in the plasma. This phase is like doubling your weekly salary for the next several months. Extraordinary!! Wow!!! It is at this phase and beyond where we are able to detect Ab in the plasma using indirect methods. If we are at the piont where we are performing a Panel then the Ab concentration is somewhere at the begining of the Exponential phase or beyond. This means that the majority of Ag sites are bound by Ab (the Lag Phase) and we are working with detectable free Ab in the plasma. So, why are we doing a DAT at this point in the first place? If we are concerned with the early release of a newly developed Ab, in addition to the Ab detected indirectly, then the DAT would be of assistance. But are we concerned with this in every case? I don't think so, and, as Malcolm has stated, "it is not worth performing a DAT with every panel". Neither is the Auto control, but I say this with caution because I am not sure of what the Auto Control is capable of detecting that has been implemented in hemolytic tranfusion reactions; Maybe Malcolm, or other posters can shed some light on this.

If we are working with a patient that has historic Ab(s), such as a Sickle Cell patient, then it would be beneficial for the patient to perform a DAT with their panel so that we can see if a "Lag Phase" Ab is present. The DAT would also be beneficial for any patient that has been transfused within the last three months that elicits a positive ABSC and that has a historic Ab or not. In this case we have seen the use of a Poly-Specific reagent so that we can detect bound complement as well. Long-story-short; the Auto Control and DAT have their place in our practice but I think a criteria of use should be established and I don't think that either test should be performed with every panel in a non-specialized hospital setting. And let us not forget that when we aquire a positive Ab screen we are most likely to perform an extented (IgG) xmatch (using the same technique for which we established the Positive ABSC to begin with) that will ensure campatibility; and I make this statement mainly for myself because I admit that I lost focus of the end result in my original post, which are compatible PC's for our patients.

Oh no, another rag! I will not push my luck anymore but I hope this helps. By the way, the text book I used when taking Immunology class in school is "Kuby Immunology." I am sure there are current editions; it is a fantastic text book.

My fellow posters,

Long-story-short; the Auto Control and DAT have their place in our practice but I think a criteria of use should be established and I don't think that either test should be performed with every panel in a non-specialized hospital setting.

May I add:

An Autocontrol is required with every panel, as one should not attempt to interpret the panel if the AC is positive, unless you have already run your auto control at the Ab Screen, and proceeded according to that result.

Indeed, establishing an SOP with baseline criteria is recommended, but then it should be left to the BB Staff to individualize the case.

E.g.: We get requests for Ab ID we first run the Ab Screen, if it negative we refund the request.

Liz :)

Dear rravkin

Thank you for your time in explaining the S phenomema, the "Exponential Phase" and the "Lag Phase", well done, it is very helpful indeed!!

Thanks :handshake

Liz

Neither is the Auto control, but I say this with caution because I am not sure of what the Auto Control is capable of detecting that has been implemented in hemolytic tranfusion reactions; Maybe Malcolm, or other posters can shed some light on this.

Yes, the auto-control can detect the beginnings of a delayed haemolytic transfusion reaction, as, of course, can the DAT, but they are much more likely to detect the subclinical delayed serological transfusion reaction. I say this because a true delayed haemolytic transfusion reaction will give other, physiological signs, such as a raised bilirubin and an unexpectedly low increase in Hb levels.

:)

May I add:

An Autocontrol is required with every panel, as one should not attempt to interpret the panel if the AC is positive, unless you have already run your auto control at the Ab Screen, and proceeded according to that result.

Indeed, establishing an SOP with baseline criteria is recommended, but then it should be left to the BB Staff to individualize the case.

E.g.: We get requests for Ab ID we first run the Ab Screen, if it negative we refund the request.

Liz :)

Liz,

Thank you for this post however, I have a little trouble understanding why one should not attempt to interpret the panel if the Auto control is positive do to the fact that the auto control using the patient cells have their own unique phenotype as compared to the panel cells. I think that you are saying that if the auto control is positive then there may be something present in the plasma outside of immune proteins that is causing in-vitro reactions. But given the unique phenotype of the patient cells how can we not say that the reaction seen in the auto control is not unique to these reactants as compared to the panels cells. I think that a better choice of cell to use in order to interpret the panel would be enzyme treated reagent cells devoid of all surface proteins (ie antigens) whereby if this reaction came up postive with patient plasma then we would surely question the validity of any positive panel cells. I have seen in practice where the auto control has come up positive when running the panel but the panel results were still interpreted, especially if we saw some negeative panel reactions. We will follow through with a DAT and carrry on from there with an eluate if necessary. One instance that I know of is when there is pan-agglugination seen in the ABSC and panel, and the auto control would help distiguish an Anti-U and an Anti-I depending on it's reaction; thus the auto control here is helpfull in determining the immune protein present, but it does not question the validity of the panel results.

Edited July 21, 201015 yr by rravkin@aol.com

Liz,

Thank you for this post however, I have a little trouble understanding why one should not attempt to interpret the panel if the Auto control is positive do to the fact that the auto control using the patient cells have their own unique phenotype as compared to the panel cells. I think that you are saying that if the auto control is positive then there may be something present in the plasma outside of immune proteins that is causing in-vitro reactions. But given the unique phenotype of the patient cells how can we not say that the reaction seen in the auto control is not unique to these reactants as compared to the panels cells. I think that a better choice of cell to use in order to interpret the panel would be enzyme treated reagent cells devoid of all surface proteins (ie antigens) whereby if this reaction came up postive with patient plasma then we would surely question the validity of any positive panel cells. I have seen in practice where the auto control has come up positive when running the panel but the panel results were still interpreted, especially if we saw some negeative panel reactions. We will follow through with a DAT and carrry on from there with an eluate if necessary. One instance that I know of is when there is pan-agglugination seen in the ABSC and panel, and the auto control would help distiguish an Anti-U and an Anti-I depending on it's reaction; thus the auto control here is helpfull in determining the immune protein present, but it does not question the validity of the panel results.

Thank you, this is good information. I did not expand, but yes I agree fully.

Liz

Thank you, this is good information. I did not expand, but yes I agree fully.

Liz

Totally agree with both of you.

As was said by those before me in this thread: if all the Abs have senstized the cells you will have a negative AC and a positive DAT.

I must be missing something. If the cells have been sensitized by all of the antibodies, how can you have a negative AC using the sensitized cells and antiglobulin reagent (assuming the cells are sensitized by IgG and or complement and those are the antiglobulin reagents used)?

Winter, I try to explain this to you, if it is not complete , someone add it please.

The DAT is positive with anti-IgA only, and the AC with no anti-IgA, so it is neg. It is the problem of reagent we use not the real neg AC.

And to another question : When AC is done with panel , in practice our laboratory did like this, the AC is positive and all panel is pos , we can suspect the autoantibodies such as anti-I ,anti-HI or others. I think this is the idea of Liz want to express. In this case, we don't do nothing to explain the panel, but try other way.

And the AC pos but DAT neg can be something not antibodies interphere the test.

Edited July 25, 201015 yr by shily
ADD SOMETHING

And to rravkin@aol.com , you mentioned use enzyme treated cells to devoid of all surface proteins (ie antigens) whereby if this reaction came up postive with patient plasma then we would surely question the validity of any positive panel cells. This ia a question, enzyme can destroy some antigen which is clinical significance, and there maybe some antibodies directly against the enzyme can interfere the test. So in our laborotory, we don't use enzyme treated cells unless necessary.

And to rravkin@aol.com , you mentioned use enzyme treated cells to devoid of all surface proteins (ie antigens) whereby if this reaction came up postive with patient plasma then we would surely question the validity of any positive panel cells. This ia a question, enzyme can destroy some antigen which is clinical significance, and there maybe some antibodies directly against the enzyme can interfere the test. So in our laborotory, we don't use enzyme treated cells unless necessary.

Yanxia,

In my post I was merely speaking of a fictious reagent cell that could be utilized as a positive control to be run with panel cells, if we were pressed to do so. The reason I brought this up is because I was understanding from the previous quoted post that an auto control was being utilized in this way, which didn't make sence to me for several reasons. I think that you would agree that if such a cell like this came up positive when running the panel any positive panel reactions would be questionable. The reality is that we do not have a control cell to run with antibody screens or panels and even though we have indirect control procedures in place to check the viability of reagent and procedure we do not really have any direct control to determine patient serum/ plasma, reagent cell, reaction viability outside of conventional serologic practices, which work real well,

especially when experienced serologists like Malcolm and others are at the helm.

Thanks rravkin@aol.com , I agree totally with you, my previous post is somewhat garble quote out of context.

"...a fictious reagent cell that could be utilized as a positive control to be run with panel cells,..."

Oh no!! that would take the fun out of our daily pondering

Liz

Edited August 3, 201015 yr by Liz
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