Jump to content

Pondering (in the UK)


Auntie-D

Recommended Posts

With the national shortage (absence) of 250iu and 500iu units of anti-D, is anyone collecting data of the number of babies with iatrogenic HDN due to overdose of prophylaxis? Could this happen? Could for example, a 13 week old foetus be exanguinated by the mother being given Rhopylac? We have been giving Rhophylac 1500iu for all gestation and some women have multiple doses.

 

I daren't ask in the lab in case someone laughs at me. I have been distinctly uneasy in issuing myultiple lots of Rhophylac for ladies under 20 weeks :(

Link to comment
Share on other sites

Hi Auntie-D,

 

Sorry to have taken so long to reply to this, but I wanted to be certain, and so I asked Dr Shubha Allard, who, in turn, asked Dr Edwin Massie and Dr Megan Rowley.

 

They have all replied, but, for some reason, I am unable to copy and paste their answers.  If you can PM me with an email address, I will pass on their answers.

 

Malcolm


Or even Edwin Massey!

Link to comment
Share on other sites

I've managed to do it, but PLEASE, if anyone feels the need to contact any of these experts, do it through me, rather than directly, otherwise I could be in deep trouble!
 
To add my point of view.....
 
If you look in Mollison (11th Ed. Ch 5.  P166) it says there are 100,000-200,000 Rh binding sites on normal RhD +ve cells (wow, that seems like a lot to me!)
 
If you give a large amount (1500 IU) of anti-D Ig to a RhD negative woman then the anti-D Ig will bind the RhD binding sites on those RhD +ve fetal cells, which are present in very small amounts relative to the mother's RhD-ve cells (0.1% fetal red cells is an FMH of about 2-3mL, 1% fetal red cells is an FMH of about 25mL).  So all the anti-D is concentrated on the few fetal cells which are then removed because lots of their binding sites are covered (also in Mollison, I love Mollison!).
 
If you give 1500 IU anti-D Ig pre-delivery and the baby is RhD positive then the anti-D Ig will cross the placenta and will bind to the fetal cells too BUT all of the fetal cells are RhD positive and each of them will get a little bit of anti-D which spreads it very thin and the small number of anti-D molecules bound to the the huge number of binding sites is insufficient to cause even a tiny bit of haemolysis.
 
That is presumably why having a maternal immune anti-D level of <1 IU/mL (which is what you get with 1500 IU anti-D Ig) is not associated with HDN and a level of >10 IU/mL is associated with HDN.  It is the 'dose' of anti-D relative to the RhD+ve binding sites. 
 
The anti-D audit (2013) dosage table is attached. 95% are using 1500 IU for RAADP, about a third use 1500 IU post delivery and a third for PSEs after 20 weeks.  And 13% are using 1500 IU for PSEs and terminations <20 weeks.
 
Megan
 
Dr Megan Rowley
Consultant Haematologist
NHS Blood and Transplant
North London Blood Centre
Charcot Road
Colindale
London NW9 5BG
 
 
 
From: Needs Malcolm
Sent: 17 November 2015 13:42
To: Massey Edwin; Allard Shubha
Cc: Rowley Megan
Subject: RE: A Query.
 
 
Thanks very much indeed Edwin.
 
Malcolm Needs CSci FIBMS
Reference Service Manager - Training
Red Cell Immunohaematology
NHSBT-Tooting Centre
75 Cranmer Terrace
Tooting
SW17 0RB
 

 

From: Massey Edwin
Sent: 13 November 2015 15:27
To: Allard Shubha; Needs Malcolm
Cc: Rowley Megan
Subject: RE: A Query.
 
 
I agree with SHubha
 
I am not aware that it has ever been described as having done harm even with large doses given in early pregnancy. weak positive DATs are seen after delivery in a proportion as you know but DAT positivity is usually not associated with significant haemolysis.
 
Even with repeated doses the level would remain in the low risk range compared with immune anti-D. Levels peak below 1IU/ml even if measured a couple of hours after an intravenous dose with a decay that eventually matches that of im anti-D.
 
Edwin
 
PS Shubha I am giving a presentation on the subject next week and planned to read the letter you sent me (twice) and respond whilst preparing for the presentation - sorry to appear slow
 
Massey
Associate Medical Director for Diagnostic and Therapeutic Services
NHS Blood and Transplant
North Bristol Park
Northway
Filton,
Bristol
BS34 7QH


 
 
 

 

From: Allard Shubha
Sent: 13 November 2015 11:32
To: Needs Malcolm
Cc: Rowley Megan; Massey Edwin
Subject: RE: A Query.
 
 
Dear Malcolm
 
I am not aware of any evidence that the higher dose is harmful in early pregnancy
 
The guidelines state a 'minimum' dose in relation to gestation so this does not preclude using the higher dose formulations
 
Megan's Anti D NCA audit will show data on how many centres using the 1500IU dose  throughout pregnancy
 
Kind regards
 
Shubha
 
Dr Shubha Allard

 

From: Needs Malcolm
Sent: 13 November 2015 11:22
To: Allard Shubha
Subject: A Query.
Importance: Low
 
 
Hi Shubha,
 
NOT URGENT!
 
This was posted on a website (PathLabTalk) to which I belong, and I would like to allay the fears, but I can't actually find anything in the literature to so do.
 

"With the national shortage (absence) of 250iu and 500iu units of anti-D, is anyone collecting data of the number of babies with iatrogenic HDN due to overdose of prophylaxis? Could this happen? Could for example, a 13 week old foetus be exanguinated by the mother being given Rhopylac? We have been giving Rhophylac 1500iu for all gestation and some women have multiple doses.

 

I daren't ask in the lab in case someone laughs at me. I have been distinctly uneasy in issuing myultiple lots of Rhophylac for ladies under 20 weeks  :("

 

Do you know of anything?

 

With best wishes,

 

Malcolm

 
Malcolm Needs CSci FIBMS
Reference Service Manager - Training
Red Cell Immunohaematology
NHSBT-Tooting Centre
75 Cranmer Terrace
Tooting
SW17 0RB
 
 

Ppt0000000.ppt

Link to comment
Share on other sites

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
  • Recently Browsing   0 members

    • No registered users viewing this page.
  • 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.