DAT & Autocontrol positive with negative cell panel

[Desoki]

Today I had case O negative female renal pt when i did antibody screen the result was cell 2 positive then i did DAT and cell panel the result was DAT positive and autocontrol poitive and some of cell panel negative.

My question is it possible DAT & Autocontrol positive and some cell panel negative?

[Malcolm Needs ☆]

Yes.

Basically, most of the auto-antibody is on the autologous red cells, with a small amount of free auto-antibody in the plasma.

The small amount of free auto-antibody in the plasma would probably sensitise all of the panel cells, but would react preferentially with some panel cells more than others (this often happens), and those with which it reacts preferentially will show agglutination in the IAT, whilst the others will not.

If, on the other hand, you treat your panel cells with a proteolytic enzyme, such as papain, you would probably find all of the panel cells show agglutination.

This is what we usually find anyway.

[Desoki]

Yes.

Basically, most of the auto-antibody is on the autologous red cells, with a small amount of free auto-antibody in the plasma.

The small amount of free auto-antibody in the plasma would probably sensitise all of the panel cells, but would react preferentially with some panel cells more than others (this often happens), and those with which it reacts preferentially will show agglutination in the IAT, whilst the others will not.

If, on the other hand, you treat your panel cells with a proteolytic enzyme, such as papain, you would probably find all of the panel cells show agglutination.

This is what we usually find anyway.

Many thanks for you Malcolm, but can I accept the result of the panel with positive autocontrol like in my case I excluded all antibody except anti K, anti C & anti Cw.

[Malcolm Needs ☆]

As long as you give C-, K- cross-match compatible blood (in the UK, we don't worry about Cw, but in your case, you may want to use Cw- blood for the cross-match), then yes.

[vilma_mt]

I'm presuming the patient has not been recently transfused.

[Desoki]

Does the elution have any benefit in this case &what is that benefit ?

[Malcolm Needs ☆]

I wouldn't have thought so, unless you want to prove to yourself that it is a pan-agglutinin.

[rravkin@aol.com]

Does the elution have any benefit in this case &what is that benefit ?

msdesoki,

Once the DAT testing shows a positive result an elution is the next logical step in identifying bound antibody.

[Malcolm Needs ☆]

msdesoki,

Once the DAT testing shows a positive result an elution is the next logical step in identifying bound antibody.

I wouldn't disagree with you for one moment, but in this case, I think that all you would get is an eluate that reacts with all red cells of common Rh type.

[N Mullis]

Excuse me for jumping in, but there is far, far too little information provided here to leap into the assumption that an autoantibody is present in the plasma. What was the transfusion history? The original post seems to be asking the question "does a positive DAT invalidate the panel results?" and the answer to that question is "No".

If you are getting clear positive and negative results in the plasma testing, I would assume that the antibody(ies) detected are alloimmune (unless the patient's cells type positive for the associated antigens, then that's a different question with a long answer). The DAT could be positive due to things such as recent transfusion (delayed transfusion reaction), certain medications, a developing autoimmune process... I would suggest evaluating the DAT by checking the medical history for transfusions and medications before going the autoantibody route. Also at least an initial elution should be performed before making the interpretation of autoantibody to confirm that a panagglutinin IS present in the eluate. Some drug-induced antibodies are not distinguishable from warm-autoantibodies except by the eluate results (which are non-reactive in routine testing in the case of drug-induced hemolytic anemia).

[L106]

I don't think we ever got an answer to the question "Has the patient been recently transfused?" Given the diagnosis of renal disease, it is very likely.

We all jumped on the bandwagon for an autoantibody, but if the patient has been recently transfused, I think the most likely (and scary) possibility of this scenario is that the patient may be experiencing a transfusion reaction. (An elution would be extremely helpful to investigate that possibility.)

Donna

[Malcolm Needs ☆]

I agree with both you and N Mullis, Donna.

I made the wrong assumption, with very little or no evidence so to do, that the patient had NOT been transfused, but looking back at the posts in this thread, you are absolutely correct in saying that the answer was never given.

If the patient HAS recently been transfused, then there is every reason to perform an elution.

Edited October 19, 2010 by Malcolm Needs

[DeeMc]

Going along with this discussion, we recently had an interesting case:

Teenage boy - no previous health issues, no transfusions; hgb 4.4g/dL

Positive antibody screen; all cells but one positive on panel (1+ to 2+) - possible anti-e specificity with positive autocontrol (gel technique)

Panel negative with LISS (tube)

DAT - Negative with polyspecific (Gel), IgG (Gel) and anti-C3 (tube).

Elution performed anyway - no reactions (Gel panel)

Additional Cold auto antibody identified. (tube panel)

Why the negative DAT?

All I can think of is an antibody with low affinity that is being removed by washing??????

[Malcolm Needs ☆]

Going along with this discussion, we recently had an interesting case:

Teenage boy - no previous health issues, no transfusions; hgb 4.4g/dL

Positive antibody screen; all cells but one positive on panel (1+ to 2+) - possible anti-e specificity with positive autocontrol (gel technique)

Panel negative with LISS (tube)

DAT - Negative with polyspecific (Gel), IgG (Gel) and anti-C3 (tube).

Elution performed anyway - no reactions (Gel panel)

Additional Cold auto antibody identified. (tube panel)

Why the negative DAT?

All I can think of is an antibody with low affinity that is being removed by washing??????

When you did the DAT, what reagents did you use? Did you include an anti-IgM? If not, it could be that the antibody was IgM, was coating the red cells, but this antibody would not necessarily activate the complement system to C3.

[DeeMc]

No, I do not have anti-IgM so I couldn't test that. But I am getting positive reactions with the serum in an IgG card for the antibody screen, the panel and the autocontrol????

[Malcolm Needs ☆]

Yes, but cards are extremely good at detecting "cold" IgM antibodies!

The reason for this is that the reactants are mixed (usually), and by that I mean they meet at the interface of plasma and red cells, at room temperature and are then put at 37oC to incubate. However, the time it takes IgM antibodies to sensitise red cells is extremely short, and it could well be that the reactions you are seeing in your IgG cards are, in fact, agglutination caused by an IgM antibody.

It could be worth your while treating the serum/plasma with something like 0.01M dithiothreitol, and then seeing if you get the same results. If it is an IgM antibody, then that should be disrupted by the treatment, and you will, therefore, get negative results with your IgG card tests (although, of course, your auto may still be positive, as the auto red cells may already be coated with the IgM antibody).

I'm not saying for one moment that IgM is the explanation; I am only saying it is one explanation (and, of course, if there is an IgG antibody there as well, treatment with DTT may not show you any different reactions anyway).

[Joanne P. Scannell]

I believe gel detects more Anti-M's because the medium is more acidic than reagents used in tube testing. Some of you may remember the old 'acidified serum' procedures ... we actually used to look for these things on purpose!

As far as cold agglutinins, just get your cards in that heating block as quickly as possible! Besides, they are easily identified ... that mixed cell reactivity gives it away quite clearly. So, in gel ... being bothered by those pesky cold agglutinins is just a 'fond' memory.

[rravkin@aol.com]

I wouldn't disagree with you for one moment, but in this case, I think that all you would get is an eluate that reacts with all red cells of common Rh type.

Malcolm,

Thank you for the response, but I'm not sure of how you arrive at your stated conclusion; and if there were this reactivity isn't that important info in determining if there is an IgG bound Ab and what specificity it has. The fact that the Auto Control and DAT are both positive would point to a bound IgG Ab and of course the eluate would lend to understanding it's specificity; But again, how do you arrive at an Rh Ab?

[Malcolm Needs ☆]

Malcolm,

Thank you for the response, but I'm not sure of how you arrive at your stated conclusion; and if there were this reactivity isn't that important info in determining if there is an IgG bound Ab and what specificity it has. The fact that the Auto Control and DAT are both positive would point to a bound IgG Ab and of course the eluate would lend to understanding it's specificity; But again, how do you arrive at an Rh Ab?

To answer this, I have to go back to my speculation that this really is an auto-antibody - see my post earlier in which I admit that I may have jumped to conclusions about this.

The reason that I state that the antibody in the eluate will probably react with all red cells of common Rh type is because the vast majority of "warm-reacting" auto-antibodies have a specificity within the Rh Blood Group System (usually, but not exclusively Rh17 or Rh18). The corresponding antigens are expressed on all red cells of the common Rh types, but would not be expressed on red cells of the rare Rh types -D- and Rh null.

Obviously, there are exceptions; some auto-antibodies have the specificity of anti-Wrb (anti-Di4). Such an auto-antibody will react with -D- and Rh null cells, but, in effect, because you would not be able to transfused a patient on a regular basis with either Rh null or Wr(b-) blood (on the grounds that there are just not sufficient units available in the world - let alone a single country), the actual specificity is irrelevant.

I hope this explanation helps, but if it doesn't, I'll have another go!

:fingerscr:fingerscr:fingerscr:fingerscr:fingerscr