Weak backtype reaction

[rravkin@aol.com]

Does anyone engage in any further testing to rule out a potential false neg ABSC do to immune supression when reverse typing reactions are ranked 1+ or less using the Ortho ProVue?

[Rh-fan]

You have a point, but we have never done that. Maybe after a transfusion reaction.

[rravkin@aol.com]

You have a point, but we have never done that. Maybe after a transfusion reaction.

Thank you Rh-Fan for going out on the limb with me. I have to say that I am surprised at the very limitted response given over a hundred views of this post.

Has this thread really stumped the crowd. I only realized this situation from a combination of practice and membership to PathLab Talk.

[galvania]

Just stumped! It would never even cross my mind to do further investigations. What would you do anyway - and why? If they haven't got any detectable irregular antibodies, due to immune deficiency, they're not likely to destroy any blood transfusion they receive - or am I being naive, here? What I'm thinking is, that they're not likely even to mount a secondary response even in the case that they had a 'hidden' antibody....

[rravkin@aol.com]

Just stumped! It would never even cross my mind to do further investigations. What would you do anyway - and why? If they haven't got any detectable irregular antibodies, due to immune deficiency, they're not likely to destroy any blood transfusion they receive - or am I being naive, here? What I'm thinking is, that they're not likely even to mount a secondary response even in the case that they had a 'hidden' antibody....

Galvania,

I am glad you asked. First off "Why"? When you hav eweak backtype then one reason for the is low concentration of ABO antibodies. One reason for this low concentration is Immune Suppression. Now , the ABO antibodies are some of the first antibodies (if not the first) produced by the immune system three months approximately after birth. The immune system then maintains throughout life

a high enough concentration such that we reutinely see no less then a 3 to 4 plus reaction when performing our backtype. The immune system does not always and in every case treat the allogenaic antibodies quite the same way. Often time concentrations in the plasma are less than that of the ABO antibodies. So if your backtype reveals a decreased concentration of ABO antibodies then your allogenaic antibody concentration has a high probability of being far less such that it may fall below the sensitivity of the Gel Card system. Now it's known and accepted that the Gel Card System has a greater level of sesitivity as compared to the tube system even with enhanced, but this is only at 15min 37C incubation. One limittation of the Gel Card System is that it offers very few enhancement options. As per the Ortho, the manufacturer of the Gel Cards that I use, the gel ingrity is lost at 30min incubation at 37C. Now the whole premise of this system is that the agglutinates are captured in the gel and prevented from migrating to the bottom of the well under centrifigul (spelling??) force. I fthe inegrity of the gel is lost then all cells and agglutinates will migrate to the bottom producing a false negative results if agglutinates were indeed present. But with the tube system one can incubate the reaction volume for an hour or longer and one can perform multiple adsorbtions as well; which begs the question, Is the gel system more sensitive than the tube system at one hour incubation? I hope we have better informed minds here then mine that may be able to answer that question. So that is the Why part, to rule out the presence of an allogenaic antibody that may have fallen under the radar of our Gel testing system.

So what additional testing should be done? Extended incubation, of course, has been know to work and perhaps multiple adsorbtions as well, or at least one addition adsorbtion prior to Coombs testing; because our initial antibody screen was negative and we are trying to rule out the presence of weak yet potentially harmful allogenaic antibody. Now is all of this testing practicle in the general hospital blood bank/ Yes! What about control of this system. One possibilty is to test a series of reagent Anti D serial dilutions such that we find a dilution that does not give any reaction in the Gel Card testing system but shows reactivity after one hour incubation using the tube testing system. For multiple adsorbtions this control would yeild no reactive after the first adsorbtion but shows reactivity after the second. Once this control is establiblished keep a volume refrigerated for the rare occasion when needed, or establish the usable dilution and just prepare as needed.

The further explaination of the Why comes from the gaol of perfecting the transfusable product and the rare adversities that can occur and the our governing organizations are trying to route out with practice. Case in point, look at Transfusion Reactions; one of the most striking facts present in the text published by the AABB are the extreme statistics of occurences for each topic; they all seem to be very rare occurences; and please forgive any over generaliztions here. So we are dealing with a rarely occuring phenomena (not including cancer treatment centers, I am sure that a weak backtype is much more frequent) that may cause insult to the care and prognosis of any of our patients.

I thank you all in advance for any feedback here. Thank you again.

[rravkin@aol.com]

[quote=rravk Galvania, an Acute Hemolytic Reaction is unlikely but we do not know if a delayed reaction can occur nor can we know the severity.

Edited August 7, 2012 by rravkin@aol.com

[Mabel Adams]

First, when I first started using Ortho gel they suggested we validate it for longer incubation so we validated it for 40 minutes and found that it worked fine. I have often pulled out weak antibodies by incubating gel for 30-40 min instead of 15. But I agree with Anna that if you are not detecting the antibody because of immune suppression (or depression) that the patient is unlikely to have a transfusion reaction. I once saw an oncology patient show some weak, equivocal reactions over several months that very, very slowly coalesced into an identifiable antibody. I chalked it up to a very suppressed immune system that could only mount a very slow response. We did not see any reaction symptoms although transfused units may not have lasted as long as expected. This patient had normal ABO antibodies as I recall.

I have also read that many patients tested about a month or three after transfusion have been found to have alloantibodies that drop below detectable levels fairly soon thereafter. We probably transfuse people like this with antigen positive units with some regularity and they don't have any clear adverse affects.

[Rh-fan]

There is a difference for the immune system between IgM antibody formation to 'sugar" structures then the formation of IgG antibodies to a protein. No or little IgM production (to sugars) will not say there is no IgG production or boostering to a protein. I do not think that it will give a acute transfusion reaction but a boostering and delayed reaction is still possible.

[galvania]

OK - I think I misunderstood the point of the original posting. What I meant in MY posting was - If there is suspected immune suppression/depression (surmised because the ABO antibodies are weak or missing) and your antibody screen is negative, should you do enhanced tests to look for atypical antibodies (like anti-Fya, Jka etc). Well, if that IS what you are saying, then I stand by what I say. If it's not detectable by standard techniques it's not likely to cause the patient any problems - and yes, I know that some Kidd antibodies can drop below the detection threshold, but that doesn't have anything to do with immune suppression/depression. So logically, if you were going to put up an enhanced technique for patients who have weak ABO antibodies, you should do it for everyone (in case you've missed a non-detectable Kidd antibody) and then your rate of positive antibody screens is going to rocket and you will find yourselves with massive increases in work, the vast majority of which will be totally unneccessary. You will have to buy lots more reagent panels, so the companies will be pleased, no doubt! As for not knowing if the patient has a delayed transfusion reaction - if it were a significant delayed transfusion reaction, then we would hear about it - like we do with the significant delayed Kidds.

On the other hand, I think you are really asking about the relative sensitivities of tube and gel for IgM ABO antibodies. Well, you are right - the gel system is not really adaptable to enhancement techniques in that sense, and if I were investigating a very weak or non-existant reverse group, short of incubating for 15mins at 4°c with double quantities of plasma/serum, there isn't anything you can do. Incubation at 1 hour in cards is NOT a good idea, especially at 37°C - you will get drying and then your results won't be valid. Also, if you add more than 100ul of plasma (less with some CAT cards) it will be too much to fit in the reaction chamber. For special tests to look for ABO antibodies, you are better off in tubes. You can add as much plasma as you like and you can 'incubate' as long as you like

[rravkin@aol.com]

Mable and Galvania,

I did not want to debate the means of investigation, however last I read the package insert of the Ortho Gel Card it stated that gel integrity started to be lost after 30min 37C incubation. I was trying to point out the fact that a weak backtype suggests a immune suppression and that an alloAb may be missed unless an extended workup is performed. What we are trying to prevent, or at least be aware of, is the anamnestic response which has been implimented in patient morbidity albeit, rarely. The families of Ab's associated are the Rh, Kell, Kidd, and Duffy systems. It seems that from the responses I've recieved here, there is no one performing any additional testing when a weak backtype occurs. Perhaps, any adverse occurence whoes only symptom is a weak backtype is so rare that it is not worth the resources to investigate.

Edited August 8, 2012 by rravkin@aol.com

[Mabel Adams]

I should probably read the recent version of the gel card instructions.

I agree with your final conclusion.

[rravkin@aol.com]

Mable,

You are correct about the 40 min time maximum for the Gel Card incubation at 37C as I found out the other night. I did neglect to mention the reagent red cells for which to crossmatch our specimen within my long post. I would naturaly use Rh positive reagent red cells for the control and I would use a selected cell panel for my patient specimen where each of the antigens would be represented homozygously. The rarity of this occurence outside of cancer, transplant, elderly, and infant populations is such that the line of testing I proposed would be feasable; even with two adsorbtions. Consider that the control antisera is either premaid or can be made up as needed once the dilution is clarified and as far as the panel cells are concerned one could easily estable the battery of cells with each new lot of panel cells. We would then be practicing incubation for one hour at 37C for each adsorbtion; a very easy procedure to work into performing other testing.

[Mabel Adams]

I must confess I am not sure how you are using adsorptions in this context. Would you be doing repeated adsorption and elution of the patient plasma sample to try to concentrate any antibodies present?

[rravkin@aol.com]

Yes, that is exactly why but I was not suggesting an elution. I would use multiple absorbtion in order to capture enough antibody to be detected by IgG.

I must confess I am not sure how you are using adsorptions in this context. Would you be doing repeated adsorption and elution of the patient plasma sample to try to concentrate any antibodies present?

Edited August 10, 2012 by rravkin@aol.com

[David Saikin]

If we have a very weak or missing reverse type we will perform the AHG xm if blood is necessary.

[John Eggington]

The original idea of this thread needs every sample from every patient to always get a 'reverse group' (i.e. the first and every subsequent sample of any patent), is this the case? Also, where do group AB patients 'stand'?

[jayinsat]

The original idea of this thread needs every sample from every patient to always get a 'reverse group' (i.e. the first and every subsequent sample of any patent), is this the case? Also, where do group AB patients 'stand'?

From a practical stand point, you have to weigh cost/time vs. risk. Like John said, how would you know if an AB patient was immunosuppressed? Do you do further testing on every AB patient? The way antibodies against low frequency antigens (Cw, V, JsA) are detected usually is via a reaction. Should we crossmatch every negative antibody screen through AHG so as to completely avoid this?

Because the risk is so low in all these cases, consensus says proceed as if there is no significan alloantibodies.

[Mabel Adams]

And I am still not convinced that the immunosuppressoin detected by a weak reverse type is proportional to that affecting alloantibodies. Maybe patients can have IgG alloantibodies suppressed while still having normal reverse types. I still think the patient whose antibody is too suppressed to react in our test will also be too suppressed to have a transfusion reaction.

[rravkin@aol.com]

Testing Post

[rravkin@aol.com]

John, Jayinsat, and Mable,

It is obvious that our testing sytems will not offer any alert for an AB patient. However, for all the rest of our patients in general a strong reacting backtype is the norm and a weak backtype is the rare occurence. David's practice at least acknowledges the possibility of a missed alloAb. From the practicle standpoint the extended testing that I've suggested is highly do-able and would not cost but a minimum in extra materials for the general population because this occurence is so rare; the only real extra cost is maybe time. Given that the ABO antibodies are the first to develope and remain strong for the most part through the course of life based on our own testing and that any detected alloAb's more often show weaker reactivity it stands to reason that our testing systems may not detect an alloAb if the backtype is weak. Although our testing methods have come a long way and offer greater levels of compatibility there are still some limitations. No one using our testing methods could definitively determine the cause of a weak backtype; but we all know that the worst error that can occur in the blood bank is the reporting of a false negative result; our antibody screen. Therefore, I was suggesting a relatively simple method to further testing to ensure that we do not miss a weakened alloAb, which as of the present poses no indication of an acute response but like we don't know the cause of the weak backtype we also don't know if or when the patient's immune system is going to start working at normal capacity either. Immagine if we actually detected an alloAb and if the patient needed red cells then we would be able to provide a more compatible product. Isn't that what blood banks do; provide compatible products. So why are we not addressing this limitation in our testing systems so that we can produce a better compatible product? This is what we do, I think.

[John Eggington]

I think you'd have to use your 'enhanced' technique on all patients, regardless of backgroup results, once you'd intoduced it. All patients would have to benefit from a more sensitive technique; you can have weak antibodies without having immune supression. I assumed David would do an AHG crossmatch because he hadn't got a vlid ABO result, not because he was worried the abs screen had given a false negative result; I'm sure he'll clarify if I've misunderstood.

[rravkin@aol.com]

John,

Certainly the enhanced technique can be used for other patients but I would think that this would be a judgement call and not a routine occurence.

And if David hadn't got a valid ABO result he would be performing a further workup to investigate an apparent ABO discrepancy not simply an extended crossmatch.

[John Eggington]

Missing a weak antibody in an immunocompetent patient would be much more significnt than missing one in an immunocompromised patient, I would have thought. . You cold justify applying a 'different' antibody id technique on a patient that gave a positive antibody screen, but every negative you encountered would need the enhanced technique. I would have thought the 'judgement call' would quicky start to fall on the side of 'caution'; who would want to be the first person to miss an antibody due to failure to apply proper judgement?

[rravkin@aol.com]

John,

I use the term "immunesuppressed" to mean that there is a weak conncentration of ABO Ab and/or alloAb. But you have stated the precise reason for any extended work with a weak backtype, "immunocompromised." This is exactly what we can not understand from our testing methods, if there is indeed a compromise at all; nor can we fully understand the length of the condition either, will it last a few hours,days,weeks, or months. To go and extrapolate this reasoning to all patients irregardless of backtype reactivity is to say that our testing systems are completely invalid, and this is just not true.

As far as missing a weak antibody in an immune competant patient, I would ask how are you judging immune competance; certainly not completely by our testing methods, you are also looking at patient history, and current condition and making a judgement call on the relative immune competance of this patient. If your backtype gives strong reactivity why would you even question the immunecompetancy; however if the backtype gives weak reactivity then there is ample reason to question the immunecompetancy because you a tangible results pointing towards immunesuppression; which, as I stated earlier, may not be the only reason, but to produce the better compatible product for this patient we should test on the side of caution.

[AMcCord]

I'm sorry, but I have to disagree that an adsorption process is easily feasible. There are many smaller facilities across this country that do not have the staffing, materials or the techs with the competency to perform adsorptions. There are many smaller facilities that don't even do antibody identification, much less adsorption, elution, enzyme treatments, etc. They send those tests to a reference facility. Their test menus are very basic and their budgets are not going to allow for extra reagents, training for testing and competency assessment materials for a test that would be done only rarely. Every time they had a patient that had a weak backtype, the crossmatch would have to be sent out, delaying transfusions by up to a day or more for rural facilities. That would make an adsorption requirement very burdensome. As to the rarity of a weak backtype, that depends on your patient population. We have a large percentage of elderly and oncology patients. I see a weak backtype or two (or three) almost every day and we do an average of only about 15 blood types daily.

Many of our transfusions are outpatients who are not prescheduled - from the time of order to checkout of the first unit is 90 minutes or less and that's the way management wants it for the benefit of the patients. Adding an adsorption step would require a delay of several hours, during which the patients would be hanging around waiting and waiting. Since most of the outpatients are Onc patients with low Hgbs who feel lousy and need the blood, that's not good patient care. What if that weak backtype was a patient in the ER with a 4.0 Hgb or a severe GI bleed? Can we tell the ordering physician, 'sorry, you're going to have to wait on that blood' or do we decide to exclude those patients from that extra step. We staff Blood Bank with 1 tech many days - if that tech has to do an adsoprtion every day or so, maybe even 2 or 3 on some days, that's going to delay the surgical crossmatches and the crossmatches on the transfuse orders, both inpatient and outpatient. The adsorption step would increase the cost of transfusion and I doubt that insurance companies would consider it a clinically necessary step, and Medicare is not going to be increasing reimbursements, so that means we'd eat the extra cost.

We don't ignore the problem of a weak backtype in terms of the ABO type. If we see a weak backtype, we increase the amount of plasma used for the backtype and the IS crossmatch. If the backtype still doesn't react (rare, thankfully), then we would have to do additional work to resolve the backtype issue and would perform an AHG crossmatch. We do not do additional work to try to detect alloantibodies. If the antibody screen is negative with solid phase or PeG, we accept the result.

There have been retrospective studies done with thousands of patients looking for adverse transfusion reactions post abbreviated crossmatch protocols (negative antibody screen/IS or electronic crossmatch only). There would have been a statistically significant number of patients with weak backtypes in those patient populations. I'm not aware of one of those studies showing an appreciable number of problems. If we were truly missing clinically significant antibodies by not using more aggressive methods to detect them, I think that it would have become apparent by now. I think we need to make an evidence based decision here. If there is evidence that more testing is beneficial, then I'm all for it. But if there is little or no evidence, then I think there is a line where we have to say that we have practised due diligence in our decisions and call it good.

Edited August 13, 2012 by AMcCord