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David Saikin

Patient with Anti-D

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I have this prenatal patient who presented with a weak anti-D,-C (G ruled out).  G4p2.

Her initial D titer was 2 f/u with 4 and 8.  After her 3rd titer she was given RhIg in the office.

My question:  are further titers a moot point?

The anti-C was not titerable initially and has been undetected in subsequent samples.

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How many weeks pregnant was she before the fool in the office gave her RhIg?

One would have hoped that, after 50 years, everyone in the office would have known NOT to give RhIg in such circumstances, but that is obviously over-optimistic.

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My first thought was, why on earth did they give the RHiG!!!!  I'm with Malcolm on that.  You great minds do think alike!!  :haha:

I really would like to hear the rational if there is any.

To answer your question, I see absolutely no value in additional titers, at least not until the next pregnancy.  

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16 minutes ago, John C. Staley said:

My first thought was, why on earth did they give the RHiG!!!!  I'm with Malcolm on that.  You great minds do think alike!!  :haha:

I really would like to hear the rational if there is any.

To answer your question, I see absolutely no value in additional titers, at least not until the next pregnancy.  

My thoughts exactly.  I don't know how far along - I'm guesstimating this was her 26 week antenatal experience.

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In that case, I have to disagree with John for once (sorry John!).

The reason I disagree is that a dose of RhIg will not give a very high titre, BUT, the titre of a pre-formed anti-D can rise very rapidly, and very dangerously, in the third trimester (much higher than the titre seen with just a dose of RhIg added to a low titre of allo-anti-D), and so, despite the complete idiocy of the person who gave the shot, I would still monitor the pregnancy by titration (well, I wouldn't, but only because in the UK we monitor anti-D in pregnancy by quantification).

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Malcolm, her titre was already rising so I don't see the need to continue.  There are better ways to monitor the fetal status during the third trimester when you know the titre is rising.  At this point, it's just numbers and academic.  

David, you indicate there were 3 titres performed, how far apart were they?  In other words, how quickly was it rising? 

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But I thought that the titre had only risen from 4 to 8?  That is only one tube, which could be caused either by a small dilution error, or by a higher number of D antigen sites on the red cells, or both, however, I do agree that there are far better ways of monitor the pregnancy, such as ultrasound.  However, that having been said, if it turns out that the titre hadn't risen to dangerous levels, would you want to worry the pregnant woman by getting her to have serial ultrasounds (or whatever)?

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If I read David's original post correctly the titre started at 2 then went to 4 and then to 8.  That's why I asked how quickly it went from 2 to 8.  If that's a relatively short time span then I would consider it significant and the RhIG dose would be a confounding factor on subsequent titrations.

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4 hours ago, John C. Staley said:

If I read David's original post correctly the titre started at 2 then went to 4 and then to 8.  That's why I asked how quickly it went from 2 to 8.  If that's a relatively short time span then I would consider it significant and the RhIG dose would be a confounding factor on subsequent titrations.

I get what you are saying John, BUT, repetitive testing on high-dose RhIg doses in cases of, for example, ITP, have shown that this does not lead to high titres of cell-free anti-D, and so I'm sorry, but I still think titrations are worth doing for a while.

Think about it.  If the TRUE titre was 4, a titre of 2 and a titre of 8 is only one tube either side of 4.  Yes, IF the true titre had gone from 2 to 4 to 8, it is a clinically significant rise, but, it could still, at this stage, be experimental error, for the reasons I gave above.

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On ‎02‎/‎29‎/‎2020 at 10:10 AM, John C. Staley said:

Malcolm, her titre was already rising so I don't see the need to continue.  There are better ways to monitor the fetal status during the third trimester when you know the titre is rising.  At this point, it's just numbers and academic.  

David, you indicate there were 3 titres performed, how far apart were they?  In other words, how quickly was it rising? 

Original specimen titer was 2.  Monthly.  Went to 4 and then 8.  (Red Cross did the first 2, I did the last as Titer was not ordered so phlebs only drew a small lavender.  ARC wants a lot more than that, as they do another abid, r/o G, and a few other things in addition to the titer ordered.

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In that case David, I would do serial titrations "in house", otherwise you will be paying out for a load of tests that you do not need.  However, do I presume that, as the first two titres were performed by ARC, and you did the third, you were unable to perform a parallel titration on the second sample, when you did the third?  If this is true, then there is even more of a possibility that the change from 4 to 8 in results may, itself, be the result of a small experimental error (with no offence meant, and I hope none taken).

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We've had this happen also, and in a perfect world I'd prefer the OBs resume titers in a bit (give the RhIg time to wane) to see if anti-D is shooting up.

We've been burned twice in the past six months where OBs stopped checking titers and switched to Dopplers, which showed decreased risk of fetal anemia, and the babes came out with peripheral blood full of erythroid precursors - right on down to erythroblasts - requiring emergent exchange.  So I personally would request a repeat titer closer to delivery, just so you know what you may be dealing with. I don't trust the Dopplers (sorry, radiology!)

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On ‎03‎/‎02‎/‎2020 at 12:13 PM, Malcolm Needs said:

 If this is true, then there is even more of a possibility that the change from 4 to 8 in results may, itself, be the result of a small experimental error (with no offence meant, and I hope none taken).

No offense at all.  Who knows if I do things the way the ARC does them . . . or even AABBs "modern method", which to me is a serial  1:3 dilution (1 drop cell suspension and 2 drops test plasma/dilutions)- though that is read microscopically.   I don't save send out titers as we do them routinely anymore here. 

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