Jump to content
PathLabTalk

Weak D+ specimens


pbaker
 Share

Recommended Posts

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.

Link to comment
Share on other sites

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.

 

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

 

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.    

Link to comment
Share on other sites

  • 3 weeks later...

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Advertisement

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.