I need help from all of the collective blood bank geniuses on this site. Anyone have a quick and dirty way to differentiate between Rhogam anti-D and the real thing, besides titering? I was thinking maybe one might be pos at immediate spin but want to know what you all think.

Sorry Lara, but I don't think there is.

Certainly, if the anti-D is high titre, then it is going to be immune (but you don't need me to tell you that)!

If the anti-D titre is low, then it could be either prophylactic or immune (and, again, you don't need me to tell you that).

The only thing I can suggest is that Rhogam would be produced from a number of donors, whereas the patient would be producing the anti-D herself. Therefore, if you Gm and Km type the anti-D, if it were the patient's own imune anti-D, then the Gm and Km type would be her own, whereas, if there were a mixture of Gm and Km types, it is more likely to be Rhogam (but even then, if she is only just beginning to produce her own anti-D, and she had been given Rhogam, there is a fair chance that her own Gm and Km types would be "hidden" amongst those expressed by the Rhogam donors).

On top of that, Gm and Km typing is a pain and (serologically) not the most exact of sciences.

So, all in all, this post isn't going to be the most encouraging that you have ever read.

SORRY!

:redface::redface::redface:

Malcolm has hit the nail on the head (as usual) . . . we report these out as "probably residual antenatal RhIG" and request a repeat 3-4 months after the last dose. My OB docs have never followed up with such (and probably prudently as we have had no seroconversions).

I don't qualify to respond to this question, as I am not a blood bank genius, but I might add that if the patient's Anti-D reacts on immediate spin I would think that it is almost assuredly NOT due to passive Rh-Immune Globulin.

(Corrections are welcomed if this is a misconception.)

We call it due to RhIg if we have a negative screen from the current pregnancy and a date of RhIg injection. We call it possibly due to RhIg if we have a date of RhIg injection, but no history of screen during the current pregnancy.

I need help from all of the collective blood bank geniuses on this site. Anyone have a quick and dirty way to differentiate between Rhogam anti-D and the real thing, besides titering? I was thinking maybe one might be pos at immediate spin but want to know what you all think.

I don't qualify to respond to this question, as I am not a blood bank genius, but I might add that if the patient's Anti-D reacts on immediate spin I would think that it is almost assuredly NOT due to passive Rh-Immune Globulin.

(Corrections are welcomed if this is a misconception.)

I've been thinking about this, and I cannot see that even a de novo immune anti-D would show up in an immediate spin, let alone Rhogam.

In almost all cases the immune anti-D will be IgG (you would be exceptionally lucky/unlucky to pick up an immune anti-D that is pure/almost pure IgM), and the Rhogam, by definition, would be IgG (early work on both sides of the Atlantic showed that the injection of IgM anti-D not only did not prevent immunization, but was actually like adding fuel to the fire), and so, unless I am missing something (like a potentiater), how would you detect either by immediate spin technique?

Am I missing something obvious to everyone else????????

By the way, I agree with your post adiescast, although we do also like to know the dose of anti-D immunoglobulin given (there are several different doses used routinely in the UK, from 250IU through to 1, 500IU).

:confused::confused::confused:

Edited December 17, 200915 yr by Malcolm Needs

malcom, what do you consider a high titer....i had a 1:32 5 days after Rhogam and 5 months later it is barely 1:1 so it most probably was due to the Rhogam.

malcom, what do you consider a high titer....i had a 1:32 5 days after Rhogam and 5 months later it is barely 1:1 so it most probably was due to the Rhogam.

I am very sorry Jives, but I can't answer your question.

Here in the UK, the NHSBT does not titre any plasma containing anti-D (or anti-c come to that). We quantitate it using International Units against a standard anti-D (see the lecture on HDN in References, Document Library, User Submitted, Educational).

That having been said, we do titre all other antibody specificities and (usually) only get worried if the titre reaches 32. In so saying, I would be surprised if an antibody could reach a strength sufficient to give a titre of 32 unless it was immune.

Could I ask a couple of questions?

You say the titre was 32, 5 days after administration of Rhogam, but I would think from the fact that you also say that 5 months later the titre was barely 1.

Am I correct in assuming the Rhogam was given close to, or after birth of a baby?

Am I correct in assuming that the second sample was taken 5 months after the administration of the Rhogm?

If my assumptions are correct, I would say that the anti-D was most certainly immune, rather than passive, as the half-life of an IgG immunoglobulin is, give or take, 21 days, and so unless the lady was given a bolus dose of anti-D imunoglobulin, there is virtually no chance that you would be able to detect this passive anti-D after 5 months.

:confused::confused:

I've been thinking about this, and I cannot see that even a de novo immune anti-D would show up in an immediate spin, let alone Rhogam.

In almost all cases the immune anti-D will be IgG (you would be exceptionally lucky/unlucky to pick up an immune anti-D that is pure/almost pure IgM), and the Rhogam, by definition, would be IgG (early work on both sides of the Atlantic showed that the injection of IgM anti-D not only did not prevent immunization, but was actually like adding fuel to the fire), and so, unless I am missing something (like a potentiater), how would you detect either by immediate spin technique?

Am I missing something obvious to everyone else????????

By the way, I agree with your post adiescast, although we do also like to know the dose of anti-D immunoglobulin given (there are several different doses used routinely in the UK, from 250IU through to 1, 500IU).

:confused::confused::confused:

Presumably it is possible to catch the immune anti-D in the IgM phase, although that time frame would be very short. I was thinking the post meant that the antibody could show up at immediate spin and at Coombs and therefore is not pure IgM, but a mix. (You know what happens when you assume things...)

We only have one dosing level in our pharmacy right now, but for the life of me I can't remember what the IU level is . So technically, if my brain cells are firing at the appropriate rate, I do know what dose was given.:imslow:

Presumably it is possible to catch the immune anti-D in the IgM phase, although that time frame would be very short. I was thinking the post meant that the antibody could show up at immediate spin and at Coombs and therefore is not pure IgM, but a mix. (You know what happens when you assume things...)

We only have one dosing level in our pharmacy right now, but for the life of me I can't remember what the IU level is . So technically, if my brain cells are firing at the appropriate rate, I do know what dose was given.:imslow:

Yes, I think I am correct insaying you only use 1, 500IU (but I could well be wrong).

sorry, but i forgot to mention the rhogam she got in sept so that would account for the low titer in dec......it just surprises me that the titer of rhogam can be 32 even if it was just 5 days post injection

thanks, for the help

sorry, but i forgot to mention the rhogam she got in sept so that would account for the low titer in dec......it just surprises me that the titer of rhogam can be 32 even if it was just 5 days post injection

thanks, for the help

Unless the patient is of particularly small stature, I wouldn't so much be surprised, as amazed that the titre reached 32, and, unless the Rhogam was given in very late September, and the tests performed in very early December, I still think that the anti-D is immune.

If the lady had an immune anti-D in August/September, and Rhogam was given, then the titre could be higher than expected, as there would be a cumulative effect.

Presumably it is possible to catch the immune anti-D in the IgM phase, although that time frame would be very short.:imslow:

Even then though, an IgM anti-D tends not to "fit" the D antigen as well as does an IgG anti-D (there is an anti-I-like element to the specificity), and is still detected optimally at 37oC, I would still be surprised if it could be detected by immediate spin technique (unless it is the anti-I-like element that is being detected).

We have noticed in the last couple of years that the anti-D reactivity in patients who have recently received RhIg has been considerably higher and longer lasting than it used to be. I wondered whether the formulation has changed.

Years ago our reference lab stated they could do a "capillary test" to see if the antibody was IgM - if positive one could say it is a true Anti-D but if negative one still wouldn't know (as someone earlier stated about IgM changing to IgG after a while). We were told to check again in 6 months - if still there it is definitly a true antibody (as you know!).

Years ago our reference lab stated they could do a "capillary test" to see if the antibody was IgM

Hmmmmmmmm!

Therefore, if you Gm and Km type the anti-D, if it were the patient's own imune anti-D, then the Gm and Km type would be her own, whereas, if there were a mixture of Gm and Km types, it is more likely to be Rhogam (but even then, if she is only just beginning to produce her own anti-D, and she had been given Rhogam, there is a fair chance that her own Gm and Km types would be "hidden" amongst those expressed by the Rhogam donors).

Wow Malcolm...once again you humble me with your knowledge...I must admit to having NO knowledge whatsoever of a Gm and/or Km. An anti-G is very familair to me..I guess I didn't know there were multiple specificities of an Anti-G.

Feel free to "enlighten" me if you will.

PS. Do you ever sleep? Or do you just study/learn/work all the time??!

Currently in our hospital (not my decision, by the way) we will confirm the date of the last rhogam administration if our antibody screen "looks like" an anti-D. If the patient has received rhogam within the last couple months, we will result the antibody screen/ID as "Presumably passive Anti-D due to rhogam injection on ...(whatever date).

Wow Malcolm...once again you humble me with your knowledge...I must admit to having NO knowledge whatsoever of a Gm and/or Km. An anti-G is very familair to me..I guess I didn't know there were multiple specificities of an Anti-G.

Feel free to "enlighten" me if you will.

PS. Do you ever sleep? Or do you just study/learn/work all the time??!

Sorry if I have confused you a bit here, but Gm and Km have nothing to do with the Rh Blood Group System; indeed, they are not red cell antigens at all.

Gm stands for gamma-marker and Km for kappa-marker. These are antibody idiotypes (antigens on the gamma and kappa parts of the antibody). Each individual makes antibodies of one type (although there may be more than one allelomorph per individual, e.g. an individual may be G1m1 and G1m2). All their antibodies, whatever the specificity, will have the same Gm type and Km type. This is why I say that, if the anti-D only shows one Gm and Km type, it is probably an immune anti-D, whereas, if there are multiple Gm and Km types, it is likely to be derived from anti-D immunoglobulin; but there could also have an underlying immune anti-D present.

In other words, these idotypes can be used to rule in an immune anti-D, but not to rule out an immune anti-D. That having been said, if there are several idiotypes present, and the antibody is of low titre, it is a fair guess that it is from a dose of anti-D imunoglobulin.

I hope this explanation helps!

By the way, I'm not sure anyone does this on a regular basis any more. We used to do it when I was first working with Diana Brazier at the WHO Blood Group Reference Laboratory, but that was way back in the mid to late 1970s.

No, I do sleep, eat, drink, etc, although my wife does moan at me from time-to-time about reading books too much, but it's a hobby and she is very understanding; I guess that's one of many reasons I love her and my 10-year-old son!!!!!!

:D:D:D

Edited December 22, 200915 yr by Malcolm Needs

We simply identify it as anti-D (using the abbreviated panel) and we use a different code- DRHIG vs a-D. We also name it "Anti-D, recent RhIG injection" and include the date of the last injection. There's no way to truly differentiate the 2 antibodies so we "presume" it to be RhIG related until proven otherwise.

Regarding the change in the potency of Therapeutic anti-D. I think that you will find that manufacturers are required to meet minimum potency for a batch of product, so variation in the amount of antibody in a vial can be significant. Note also that they are required to use pharmacopoeia methods that are often old, insensitive and do correlate with modern (less than 60 years old) methods.

A parallel titre on an old and new batch with the normal method will tell the story.

We ask for RhIg injection date and prenatal antibody screen results (if we didn't perform testing). If screen was negative and RhIg was given, we call it a passive anti-D. If this information is not available, we call it anti-D (the real thing!).

Years ago our reference lab stated they could do a "capillary test" to see if the antibody was IgM - if positive one could say it is a true Anti-D but if negative one still wouldn't know (as someone earlier stated about IgM changing to IgG after a while). We were told to check again in 6 months - if still there it is definitly a true antibody (as you know!).

I agree with Malcolm...HMMMM....:mad:

I have heard of doing cell separations in capillary tubes for the purpose of antigen typing a recently transfused person. BUT....I'm not too sure about the "capillary test" to distinguish IgM from IgG antibodies!!! I am interested to hear the research you might have done to verify this statement made by your reference lab.....