AntiD level

[gagpinks]

Hi 

How often do we have to measure antiD level if women has any sensitizing event prior to 28 weeks. At 28 weeks her antibody screen will be positive due to prophylaxis anti-D. Do we always have to treat same as allo antiD (measure every 2 weeks) eventhough we have a antiD record . 

[Malcolm Needs ☆]

If the anti-D immunoglobulin was given as a result of a potentially sensitizing event (as opposed to routine antienatal anti-D immunoglobulin prophylaxis), I would think that it is very sensible to monitor the antibody on a regular basis.  The reasoning behind this is that, although you know that the lady has been given anti-D prophylaxis, unless you continue to monitor her, knowing that there has been a potentially sensitizing event, you do not know for certain that the anti-D immunoglobulin has "worked".  It may be that she had already become sensitized to the D antigen, and, if you do not monitor the antibody, it may reach dangerous levels for the fetus before you realise.

You may like to look up a couple of guidelines that have been issued recently in the UK on the subject.

The first of these is the Royal College of Obstetrics and Gynaecology Greentop Guideline Number 65 - The management of women with red cell antibodies in pregnancy.

The other is White J, Qureshi H, Massey E, Needs M, Byrne G, Daniels G, Allard S & British Committee for Standards in Haematology.  Guideline for blood grouping and res cell antibody testing in pregnancy.  This is about to be published in Transfusion Medicine, but has already been published on line (doi: 10.1111/tme.12299).

[R1R2]

14 hours ago, gagpinks said:

Hi 

How often do we have to measure antiD level if women has any sensitizing event prior to 28 weeks. At 28 weeks her antibody screen will be positive due to prophylaxis anti-D. Do we always have to treat same as allo antiD (measure every 2 weeks) eventhough we have a antiD record . 

Is there a record of a negative antibody screen before her first dose of RhIG? 

[gagpinks]

17 hours ago, gagpinks said:

Hi 

How often do we have to measure antiD level if women has any sensitizing event prior to 28 weeks. At 28 weeks her antibody screen will be positive due to prophylaxis anti-D. Do we always have to treat same as allo antiD (measure every 2 weeks) eventhough we have a antiD record . 

Yes she was negative prior to her first injection.  

[gagpinks]

Thanks Malcolm.!!  

 

 

 

[StevenB]

In regards to frequency, if the titer is less than 16 we recommend performing titers every 4 weeks after 18-20 weeks gestation, then every 2 weeks at the 34th week. 

As usual, Malcolm is spot on!

[Malcolm Needs ☆]

4 hours ago, R1R2 said:

Is there a record of a negative antibody screen before her first dose of RhIG? 

If it was just a case of routine antenatal anti-D immunoglobulin prophylaxis (RADDP), then I totally agree with you R1R2, that this question is very relevant.  This is because it is easy to see, under these circumstances, the anti-D levels keeping level, or even dropping, and we also know that the aldy has been given anti-D immunoglobulin ptophylaxis.  However, and this is the important point, gagpinks has told us that the anti-D immunoglobulin was not given as RADDP, but was given as the result of a potentially sensitizing event.  At such a stage, we do not know (CANNOT know) if the lady has already been sensitised against the D antigen by the potential bleed from the foetus to the mother.  Never forget the early work of the likes of Professor Patrick Mollison who showed that, after a primary immunisation, it can take some time (usually 12 weeks) for the anti-D to show up in the circulation, BUT, if the bleed continues as a chronic bleed, the anti-D immunoglobulin will be exhausted by the continuous bleed, after which, if there is a chronic bleed, the foetal erythrocytes will act as a secondary immunisation, and the anti-D level could well rise extremely quickly.

Now, I know this is a rare event, but, for the sake of a few extra tests, surely it would be better to monitor the pregnancy than save a few pounds/dollars?

[gagpinks]

Yes her antibody screen was negative at 12 weeks.

There is little bit confusion about new guidelines. Sometimes we get report from ref lab no further sample required in this pregnancy. If this is the case do we have to measure upto delivery? 

[Malcolm Needs ☆]

I believe you work in the UK gagpinks?  If that is so, you should only get such reports when there has ONLY been RADDP, rather than when there has been a dose of anti-D given for a potentially sensitising event - UNLESS AN NHSBT CONSULTANT SAYS OTHERWISE.

If the anti-D immunoglobulin has been given following a potential sensitising event, it would be a brave (or foolish) Reference Laboratory that issues such a report, until the anti-D in the lady's circulation mimics EXACTLY the scenarios given in the new BCSH Guidelines referenced earlier.

[R1R2]

On ‎6‎/‎8‎/‎2016 at 0:25 PM, gagpinks said:

Yes her antibody screen was negative at 12 weeks.

There is little bit confusion about new guidelines. Sometimes we get report from ref lab no further sample required in this pregnancy. If this is the case do we have to measure upto delivery? 

We would titer if requested by physician.    

[gagpinks]

Hello USA friend. 

What method do you use to measure anti-D level. If you are measuring  titre what is significant level  of titre which can cause HDFN ?