Rh D discrepancies with method changes

[ChrisW]

For those who have switched testing methods from Echo, Neo or Tube to Gel, do you find discrepancies in D antigen typing with Gel vs. historic results from other methods? How are you addressing those?

[Malcolm Needs ☆]

My laboratory certainly found discrepancies between tube and gel technology, which was hardly surprising considering the difference in sensitivity between the technologies, but, at the same time, there have been many changes in monoclonal anti-D reagent specificity (which has helped enormously in serological ways, but has not helped one iota in terms of making it easy to explain away differences in results - particularly to lay people like patients, nurses, midwives and doctors!

We are addressing these differences, and how to explain them, very, very carefully indeed!!!!!!!!!!!!!

[ChrisW]

When we first started using Microplate methods with automation, we saw this also, and had developed a method to deal with and explain discrepancies between tube and automation. Now we seem to be back a square 1 again with discrepancies! YUK!

 

[Bb_in_the_rain]

5 hours ago, ChrisW said:

For those who have switched testing methods from Echo, Neo or Tube to Gel, do you find discrepancies in D antigen typing with Gel vs. historic results from other methods? How are you addressing those?

When we have these in our central transfusion services, we look into it a bit deeper here in IRL. We repeat tube method using 3 different sources of anti-D. If all 3 sources were negative, report RhD negative. If all 3 sources were >2+, report RhD positive. If 1 of 3 sources were <2+, refer to genomic testing looking for WeakD type 1, type 2 or type 3 (if patient is female childbearing age or <18 year old). Genomic WeakD type 1, 2 or 3 were treat it as RhD Positive. If not genomic WeakD type 1, 2 or 3, treat it as RhD negative. 

If 1 of 3 sources were <2+, all 3 sources give positive reactions and patient does not have anti-D and patient is not female of childbearing age or pediatric (<18 year old), report as RhD positive. (if the patient, later on, makes anti-D change it to RhD negative)

 

Phew.!! I think the decision overall is more based on the patient's age and demographic.

Edited September 30, 2017 by dothandar

[galvania]

But look on the positive side.  If you are seeing a discrepancy, this should alert you to the presence of a variant that you might not have known was there otherwise

[kate murphy]

Here in a transfusion service, we usually say discrepancies are due to either monoclonal vs human origin, or sensitivity of methods.  It depends on strength of reaction (<2+), sex and age of the patient how we treat them.  Women of child-bearing age (<50) we usually go with Rh neg. 

[Malcolm Needs ☆]

57 minutes ago, galvania said:

But look on the positive side.  If you are seeing a discrepancy, this should alert you to the presence of a variant that you might not have known was there otherwise

But surely Anna, as most variants of RHD result in us treating them as D-, we are looking at the NEGATIVE, as they can make anti-D if stimulated so to do!!!!!!!!!  Hahahahahahahahah!  

[galvania]

Can you hear me groaning ?

[Rapundaa]

We have been using the Galileo and Neo for 12 years. Yes we have seen issues with the Rh typing being positive on previously negative patients. Our protocol is similar to Dothandar.

[osborn32]

Gel is known to display stronger D reactivity than both solid phase and tube.  I've heard the explanation is due to the pentamer form of IgM, which is trapped in gel causing a stronger positive.  Galileo/Neo/Echo and tube all use hemagglutination.  I've also seen this when moving from Galileo to gel.  If we didn't already have Rh Neg and Weak D histories on our patients and donors from the Galileo, we likely would've missed these Weak D patients in gel, scary!   Our protocol with gel was to retest all D reactions less than or equal to 2+ by another method.  Then molecular genotype RHD for those suspected as Weak D. 

[Malcolm Needs ☆]

51 minutes ago, osborn32 said:

Gel is known to display stronger D reactivity than both solid phase and tube.  I've heard the explanation is due to the pentamer form of IgM, which is trapped in gel causing a stronger positive.  Galileo/Neo/Echo and tube all use hemagglutination.  I've also seen this when moving from Galileo to gel.  If we didn't already have Rh Neg and Weak D histories on our patients and donors from the Galileo, we likely would've missed these Weak D patients in gel, scary!   Our protocol with gel was to retest all D reactions less than or equal to 2+ by another method.  Then molecular genotype RHD for those suspected as Weak D. 

I would agree with a lot of what you say osborn32, but I would take issue with one thing.

I am not in the least scared about missing Weak or Partial D types in patients, as that means they will be typed as D Negative, and so transfused with D Negative blood.  Certainly, in the UK, we use anti-D reagents in hospital laboratories that are specifically designed not to detect Partial DVI Types 1 to 4, so we consciously type some patients as D Negative, when we know that they could be Partial D.

What would scare me is mistyping donors - but the anti-D used in donor centres in the UK is specifically designed to detect Partial DVI Types 1 to 4.

Edited October 26, 2017 by Malcolm Needs
Spelling.

[galvania]

And I would like to stress one thing.  There is NO serological method that will allow you to detect ALL partial and weak Ds.  Variant Ds come in all shapes and sizes.  There are some weak Ds that have so few D antigens that the most sensitive 'normal' serological techniques will not pick them up - they will be typed as D- (including donors).  On the other hand, some partial Ds have a sufficiently high number of D antigen sites that you will detect them as a normal D+ (even patients).  And there are some Partial Ds that react with all commercially available Anti-D clones.  So you will pull these up too as D+ (even for patients).

The message behind this  is - You WILL misgroup some D variant patients as D+ and you WILL misgroup some D variant donors as D-.  And you have been misgrouping them for ever.  Until (and if) genotyping becomes as easy, fast and cheap to do for every routine group, then you have to learn to live with it!

[Malcolm Needs ☆]

I ABSOLUTELY agree with Anna.

D_EL type is so called because the fact that anti-D is adsorbed onto the very few D antigens on the red cell surface can only be detected serologically by eluting that anti-D back off, and testing the eluate with a "normal" D Positive red cell, or detected by molecular techniques.

Partial DIII types, which regularly produce a strong allo-anti-D when stimulated to so do, not only react positively with all monoclonal anti-D reagents so far produced, but, unlike most Weak D and Partial D types, actually have exalted expression of the D antigen.  In this case, the only way I know of to identify such patients is either by the fact that they are D Positive with an allo-anti-D (grounds for suspicion) or by molecular methods (usually, if not almost exclusively, after the individual has produced an allo-anti-D).