Significant Decrease In Antibody Titer

[johna]

I posted this on the AABB website this morning but thought I would also post it here to cover both bases.

A prenatal patient who we have been following monthly since July has demonstrated anti-D titers ranging from 4 to 8 and Anti-C titers ranging from 8 to 16 up until September. An October specimen gave a titers of both anti-D and anti-C at 32. Approximately 12 days later we received another specimen in which the anti-D titer was 4 and the anti-C titer 8. Three weeks later another specimen was tested and the titers were recorded as anti-D 4 and anti-C 16.

Now for the problem. The patient's physician is insisting that the October results of 32 had to have been an error. We had parallel titered this with the November specimen and the same results as previously reported in November were obtained (anti-D 4 & anti-C 16). Nevertheless the physician is insisting that it is virtually impossible for a titer to drop this significantly in 12 days. Has anyone experienced a similar situation? Thanks!

[Malcolm Needs ☆]

I posted this on the AABB website this morning but thought I would also post it here to cover both bases.

A prenatal patient who we have been following monthly since July has demonstrated anti-D titers ranging from 4 to 8 and Anti-C titers ranging from 8 to 16 up until September. An October specimen gave a titers of both anti-D and anti-C at 32. Approximately 12 days later we received another specimen in which the anti-D titer was 4 and the anti-C titer 8. Three weeks later another specimen was tested and the titers were recorded as anti-D 4 and anti-C 16.

Now for the problem. The patient's physician is insisting that the October results of 32 had to have been an error. We had parallel titered this with the November specimen and the same results as previously reported in November were obtained (anti-D 4 & anti-C 16). Nevertheless the physician is insisting that it is virtually impossible for a titer to drop this significantly in 12 days. Has anyone experienced a similar situation? Thanks!

Yes, and it is usually to do with the number of antigen sites on the red cells, rather than an antibody difference. That having been said, the antibody titre could well have not changed at all, but it may also be a factor of titration not being that sensitive (a difference of 1 tube is often seen between workers or between two individuals performing the titration on two different occasions).

The fact that the anti-C was stronger than the anti-D makes me wonder if the antibody was actually anti-G? I would imagine that the baby was clinically unaffected?

:confused::confused:

[Yanxia]

Yes, and it is usually to do with the number of antigen sites on the red cells, rather than an antibody difference. That having been said, the antibody titre could well have not changed at all, but it may also be a factor of titration not being that sensitive (a difference of 1 tube is often seen between workers or between two individuals performing the titration on two different occasions).

The fact that the anti-C was stronger than the anti-D makes me wonder if the antibody was actually anti-G? I would imagine that the baby was clinically unaffected?

:confused::confused:

But they do the test again ,and paralell with another specimen, the result is same, so I don't agree with you that the factor is antigen sites differ.

Why you think anti-G make the result of anti-C was stronger than anti-D and why the baby was clinically unaffected? Thank you!

[Abdulhameed Al-Attas]

1- Was the patient in October at the time of sample collection dehydrated?

2- Did the patient between October to 12 days later receive any infusions that would have caused dilution of ABT?

3- Furthermore,Technical factors must NOT be over looked such as:

a - Phenotype of cells used in the Titrations----? same !

b - Technical skill of technologist if not by same technologist.

c - Variations in methods.

d - Scoring/ interpreting end point of Titration.

I also share with Shily,her concern Why Anti-C titre could be > than Anti-D if it were a case of Anti-G.

[Malcolm Needs ☆]

As the titration result was the same upon repeat, it may not have been due to antigen site number, but it still may have been.

The reason I suggested anti-G (or anti-G+C) rather than anti-C+D is that, in most cases involving anti-G (or anti-G+C) reactions with R1R1 and r'r red cells are usually stronger than with Ro or R2R2 red cells (and it must be remembered that R2R2 red cells, on average, tend to have the highest number of D antigen sites amongst the "normal" D+ Rh types). In this case the anti-C titre was consistently higher than the anti-D titre, strongly suggesting an anti-G (or anti-G+C), rather than an anti-C+D. None of this is, of course, conclusive until proven (as is the presence of anti-C+D), but it is highly suggestive.

Anti-G does occasionally cause clinically significant haemolytic disease of the newborn, but it is rare.

Clinically significant haemolytic disease of the newborn caused by anti-C, especially at this titre, is exceedingly rare.

I would be interested, not only in the clinical condition of the baby at birth, but also if the baby was r'r, rather than D+? I note that the "baby" would now be 4!

:confused::confused::confused:

Edited October 23, 2009 by Malcolm Needs
Poor maths, as well as poor spelling!

[L106]

I would be interested, not only in the clinical condition of the baby at birth, but also if the baby was r'r, rather than D+? I note that the "baby" would now be 4!

:confused::confused::confused:

That's OK that we're a little late addressing this "not-so-new baby". I'm sure that many of us picked up a little more knowledge from the postings in this thread, so it was productive!