Weak D+ specimens

[pbaker]

We are adding weak D testing to our automation menu and are attempting our validations.  We have plenty of weak D negative specimens to run, but no weak D positive specimens.  I contacted our blood supplier, but they send their specimen processing out, so they no longer have samples to share with us.  Does anyone no of a way to manufacture a weak D positive cell?  Or any other suggestions where we might be able to obtain some for our validation.

[Malcolm Needs ★]

Well, first things first - there is no such thing as a Weak D Positive red cell, as there is no such thing as "anti-Weak D"!

[SMILLER]

What Malcolm?  No anti-weak D antisera available in the U.K.?

(There is such a thing as an auntie weak D, however.)  My father's sister was a terrible center-back when playing for Suffolk.

Scott

[SMILLER]

If you are concerned about validation, I suggest you contact your manufacturer.  You customer rep should be able to provide you with a list of labs that have already done what you are trying to do -- they should be able to help.

Scott

[goodchild]

1 hour ago, SMILLER said:

What Malcolm?  No anti-weak D antisera available in the U.K.?

(There is such a thing as an auntie weak D, however.)  My father's sister was a terrible center-back when playing for Suffolk.

Scott

That was beautifully random and much appreciated on a Monday morning.

[carolyn swickard]

I can't think of a way to manufacture a true weak D specimen.  Maybe try an RH neg specimen and add one drop of Rh pos cells until you get a weak reaction with your AHG phase testing, but still can't see it at Immediate spin - ???

Some manufacturers have a Weak D Pos cell for testing - but that would still take a while to have more than 1-2 donors.

 

[Malcolm Needs ★]

26 minutes ago, cswickard said:

Maybe try an RH neg specimen and add one drop of Rh pos cells until you get a weak reaction with your AHG phase testing, but still can't see it at Immediate spin - ???

 

I am sorry, but this is so wrong on so many levels.  A Weak D is not just a mixture of D Negative red cells with a few D Positive red cells to give a weak mixed-field reaction.  The various Weak D types have individual genetic mutations from the wild-type RHD gene - and it is these mutations that cause the weakness of the reaction.  Using a genuine Weak D is the only solution, as the reaction in this case, as with all antibody/antigen reactions, follows the Law of Mass Action.

[carolyn swickard]

Yeah - I knew that, but you are going to need a whole year (or even two) to get enough real specimens for validation without some help from a manufacturer or a reference lab - maybe?

[exlimey]

1 hour ago, cswickard said:

Yeah - I knew that, but you are going to need a whole year (or even two) to get enough real specimens for validation without some help from a manufacturer or a reference lab - maybe?

First, a disclaimer: I am not a Regulatory expert.

Perhaps you're over-stretching? I don't think you're required to validate the new system in the sense that the manufacturer has to do for licensing - that's a LOT of work and an attempt to cover every variable imaginable.

In your case, perhaps just proving the system works in your facility is enough. That would probably only need to include a couple of examples of weak-D, rather than the whole gamut.

[Malcolm Needs ★]

1 hour ago, exlimey said:

In your case, perhaps just proving the system works in your facility is enough. That would probably only need to include a couple of examples of weak-D, rather than the whole gamut.

I don't know of ANY "serological" laboratory that has the ability (or the necessity) to test the whole gamut of Weak D types (and I don't think anyone could - as many of them are unique to the proband), but, I would have thought, as long as you know you can detect a Weak D Type 2 (which is the "weakest" of the normal "Weak D" types, you should be covered) -  you should be okay.

[carolyn swickard]

Quote

I can't think of a way to manufacture a true weak D specimen.  Maybe try an RH neg specimen and add one drop of Rh pos cells until you get a weak reaction with your AHG phase testing, but still can't see it at Immediate spin - ???

Apologies to all - this is, of course, incorrect.  This would in no way replicate the molecular variations of the D antigen known as Weak Ds.  Don't know where my brain was this am.  I think my brain went back to what we did for validation of the Fetal Screen test when they brought out the newer models a few years ago. 

Again - apologies to all.

 

[exlimey]

16 hours ago, Malcolm Needs said:

I don't know of ANY "serological" laboratory that has the ability (or the necessity) to test the whole gamut of Weak D types (and I don't think anyone could - as many of them are unique to the proband), but, I would have thought, as long as you know you can detect a Weak D Type 2 (which is the "weakest" of the normal "Weak D" types, you should be covered) -  you should be okay.

I concur. A good writer should be able to finagle that logic into a validation plan. Getting hold of said cells may still be problematic, but at least it might be simpler than an expedition to catch the Loch Ness Monster.

[galvania]

I quite fancy an expedition to Loch Ness - with or without the monster......

[R1R2]

21 hours ago, exlimey said:

First, a disclaimer: I am not a Regulatory expert.

Perhaps you're over-stretching? I don't think you're required to validate the new system in the sense that the manufacturer has to do for licensing - that's a LOT of work and an attempt to cover every variable imaginable.

In your case, perhaps just proving the system works in your facility is enough. That would probably only need to include a couple of examples of weak-D, rather than the whole gamut.

I agree with exlimey,  perhaps validate that your instrumentation can perform antigen typing with antisera that requires AHG phase or uses AHG cards.    

[AMcCord]

On 5/16/2017 at 7:07 AM, galvania said:

I quite fancy an expedition to Loch Ness - with or without the monster......

I have one planned for later this year. The monster would definitely be more fun than weak D.

[Simon1994]

On 5/18/2017 at 4:50 PM, AMcCord said:

I have one planned for later this year. The monster would definitely be more fun than weak D.

Yes, Indeed it will be more fun.