To R/O or not to R/O

[SMILLER]

We have a patient with a history of Lua. According to our policy, if her screen is negative (there are no Lua pos cells on our 3-cell screen panel), we check for reactivity with three Lua positive cells taken from our ID panels.  If anti-Lua is showing up, we would release AHG compatible blood, if needed, without having to check at all for Lua antigen.

 

If the anti-Lua is not showing up at all, we would have to order confirmed Lua neg units from our blood supplier (ain't got none of that fancy anti-Lua reagent here) and crossmatch those.

 

Question: assuming the screen is negative and the three Lua positive cells from other panels are all positive with the patient's plasma, do we in this case have to rule out all the other antigens as well? (we use a 3 x 3 r/i r/o rule here)

 

Scott

[Malcolm Needs ☆]

Hi Scott,

I can understand that, if the anti-Lua can be detected, you give cross-matched compatible blood.

If your screen is negative, and your three Lu(a+) red cell samples give a positive result, I certainly wouldn't bother doing anything else.

What I do not understand is, if the anti-Lua is undetected, why on Earth you would get in confirmed Lu(a-) units. Unusually, ALL of the textbooks agree that anti-Lua has never caused a transfusion reaction (only anti-Lu8 has that dubious honour). Surely, that must cost you an awful lot of money for no return? Certainly, in the UK, if a hospital asks for Lu(a-) blood for a patient who has anti-Lua (let alone one that cannot be detected), we would tell them to "get on their bike"! - politely, of course!

[SMILLER]

No, I agree with the bit about anti-Lua hardly being a problem one would have to really worry about, but it is our current policy that if an antibody (on a patient who is known to have produced that antibody) is not detectable, we are obligated to not transfuse antigen-positive units if at all possible.  (We have some exceptions but Lua is not one of those).

 

I am curious to see if anyone thinks that rule outs still need to be completed for other significant antibodies when you have positive results in the above situation.

 

Thanks, Scott

[R1R2]

I would not think that you would have to run other rule outs and  I wouldn't bother testing 3 Lua+ cells, just 1 would do. Some labs would not confirm at all and just go right to AHG compatible blood.  I agree with Malcolm in that Lua is not an antibody to spend time worrying about.   Our blood supplier would die laughing if we asked for Lua negative blood.   

[jayinsat]

 

We have a patient with a history of Lua. According to our policy, if her screen is negative....

If the antibody screen is negative, regardless of whether there is a Lua positive cell on the screen or not, we would give AHG compatible XM units and never look back. 

[SMILLER]

OK, forget about Lua or Lewis antibodies or whatever.  I am not interested in that.  Think of this as aphilisophical question regarding the trustworthyness of using a 2 or 3 cell screen in the following situation:

 

Hypothetically: If for some unspecified reason, you have positive cells from a panel and a negative screen, do you do rule outs for significant antigens?  In other words, does the negative screen suffice, in a case where you know there are equivocal reactions with panel cells, to not have to worry about any rule-outs?

 

Scott

[goodchild]

OK, forget about Lua or Lewis antibodies or whatever.  I am not interested in that.  Think of this as aphilisophical question regarding the trustworthyness of using a 2 or 3 cell screen in the following situation:

 

Hypothetically: If for some unspecified reason, you have positive cells from a panel and a negative screen, do you do rule outs for significant antigens?  In other words, does the negative screen suffice, in a case where you know there are equivocal reactions with panel cells, to not have to worry about any rule-outs?

 

Scott

 

I've read that three times now and I'm still not sure what you're asking. Bleh and it's not even Monday...

[SMILLER]

LOL!

[mollyredone]

I think significant antigens are usually represented on the screening cells, although not all homozygously.  If the screen is negative, we don't go any further.  Just give antigen negative AHG XM'd units for the "biggie" antigens (Kidd, Duffy, Rh,S, Kell and a few more I'm sure I'm forgetting) and AHG XM compatible units for Lua, Lea, Kpa, M,N and the like.  Other hospitals may have different policies, but this is ours.

[StevenB]

If you have reactivity, you need to explore what is causing it. So in your hypothetical; the fact that you have negative screen cells has zero bearing on the positive reactions seen with the panel testing. You would not be able to report out a negative antibody screen in the presence of positive panel results.....at least I would never recommend it to any of my customers.

So, if a tech was unfortunate enough to shotgun a test and set-up a screen and panel at the same time, the reactive panel would trump the negative screen...you can't just ignore reactivity.

[catchmenow51]

I'm with StevenB. Any positive reactions, no matter what screen/panel they are from, have to be investigated.

[tbostock]

If you have reactivity, you need to explore what is causing it. So in your hypothetical; the fact that you have negative screen cells has zero bearing on the positive reactions seen with the panel testing. You would not be able to report out a negative antibody screen in the presence of positive panel results.....at least I would never recommend it to any of my customers.

So, if a tech was unfortunate enough to shotgun a test and set-up a screen and panel at the same time, the reactive panel would trump the negative screen...you can't just ignore reactivity.

I was wondering why the panel was done if the screen is negative; now I get it, if someone is trying to get a jump on the workup by doing both at the same time.  So yes, you would want to do more investigation to see what is reacting.

 

On a patient with known antibodies and we are now getting a negative screen, if we perform AHG crossmatches and get a rare incompatible crossmatch, we would probably investigate a positive DAT on the unit and/or seeing if the patient has now developed an antibody to a low incidence antigen.

[SMILLER]

OK, at least a few posters understand what I was getting at (even though I was  not sure myself)...

 

Now, in my original case, I have a negative screen but ran a positve Lua cell from a panel to confirm that the patient's historical anti-Lua is reacting.  (Now I can issue any AHG matched unit - because if one happens to be Lua antigen positive, I know it will be incompatible as the patient is currently producing anti-Lua).

 

But now with a positive reaction on the Lua panel cell, do I have to first continue with all of the other important rule outs?

 

Scott

[tbostock]

I wouldn't; they were ruled out in your antibody screen.

[Malcolm Needs ☆]

Exactly my point earlier Terri.

[SMILLER]

There seems to be a split in opinion here after all...

 

I think an argument might involve the definition of a "rule out".  If you take a 2 or 3 cell screen as just a screen, and not a definitive test to "rule out" all significant antibodies, then perhaps we can say taht the techniques for interpreting a screen and a panel do not need to be the same?  

 

On the other hand, if you think that all cells used for antibody testing are the same, whether in groups of 3 or 11 or 16, then I can see where one would be beholden to whatever system one uses to "rule out/rule in" when dealing with problem antibodies.

 

On the third hand, perhaps the whole concept of rule-outs based on some arbitrary critical number (or imaginary p-value or whatever), to rule out/in antibodies is somewhat bogus in the first place.  After all, for most of our T&S patients, we routinely use only 2 or 3 screening cells to imply that we have "ruled out" any problem antibodies.  Why do most of us expand the number of cells used for rule-outs when we go to a panel?

 

Scott

[Dansket]

Antibody Screen and Antibody Identification are linked but separate processes with different purposes.

 

A negative antibody screen with a minimum of 2 cells has been established by blood bank regulators as a decision point regarding the requirement to perform an antiglobulin crossmatch prior to transfusion. An antibody screen is intended to detect unexpected antibody, not to identify it.  Identification requires different criteria.

 

Therefore, an antibody screen is an acceptable method to 'rule-out' the presence of unexpected antibody in patient blood sample. 

[kirkaw]

OK, forget about Lua or Lewis antibodies or whatever.  I am not interested in that.  Think of this as aphilisophical question regarding the trustworthyness of using a 2 or 3 cell screen in the following situation:

 

Hypothetically: If for some unspecified reason, you have positive cells from a panel and a negative screen, do you do rule outs for significant antigens?  In other words, does the negative screen suffice, in a case where you know there are equivocal reactions with panel cells, to not have to worry about any rule-outs?

 

Scott

I think yes, you trust the negative antibody screen. This is what we do every day. When we get a negative antibody screen, we don't run cells positive for low frequency antigens just in case, even though we don't know if the patient has been transfused and may have an antibody titer that has fallen to undetectable levels. That is what the Coombs crossmatch is for. If you get an incompatible crossmatch, you would do more investigation to find out why

[goodchild]

OK, forget about Lua or Lewis antibodies or whatever.  I am not interested in that.  Think of this as aphilisophical question regarding the trustworthyness of using a 2 or 3 cell screen in the following situation:

 

Hypothetically: If for some unspecified reason, you have positive cells from a panel and a negative screen, do you do rule outs for significant antigens?  In other words, does the negative screen suffice, in a case where you know there are equivocal reactions with panel cells, to not have to worry about any rule-outs?

 

Scott

 

I think I'm following now and we see this occasionally here. e.g. someone is being proactive on a patient with a history of anti-E and runs the 2 or 3 additional selected rule out cells + AC at the same time or at least prior to the completion of the antibody screen and you end up with unexpected reactions in the panel and a negative screen.

 

Those situations lead to additional testing for us. While we do transfuse patients without history of antibodies based on a negative screen, if we have a known history of antibody/transfusion, and get an unexpected reaction we would want to know what we're seeing. Especially since our AB ID testing is manual gel and our Type and Screens are on the ProVue and Ortho only promises 98% concordance with a 95% confidence level between the two.

 

Now, if the positive panel cell was known to be positive for a patient's low incidence antibody and we had sufficient rule outs from the other cells tested, that's a completely different story.

Edited November 3, 2015 by goodchild

[amym1586]

On an antibody panel can you cross out  a panel cell that is non reactive for a K+k+

Edited January 19, 2016 by amym1586

[Dansket]

41 minutes ago, amym1586 said:

On an antibody panel can you cross out  a panel cell that is non reactive for a K+k+

Yes, I will rule out anti-K with a single non-reactive K+k+ panel cell.

[Malcolm Needs ☆]

So would I, with the caveat that I have seen one or two EXCEEDINGLY RARE examples of anti-K that only react with K+k- red cells.

Both, as it happens, were transfused with K+k+ units of blood, and NEITHER had any clinically significant sequelae.

[goodchild]

It seems like we're always an outlier. We look for two negative K+k+ panel cells.

[pinktoptube]

11 hours ago, goodchild said:

It seems like we're always an outlier. We look for two negative K+k+ panel cells.

Same

[Eagle Eye]

On 1/20/2016 at 8:22 AM, goodchild said:

It seems like we're always an outlier. We look for two negative K+k+ panel cells.

WE DO THE SAME.