Establishing Critical Values for Prenatal Antibody Titers

[swede]

We have been doing antibody titration forever, but a doctor will not use our lab because we do not have critical values for our lab based on patient outcome. We have always used 32 for anti-D and 8 for anti-Kell based on the tech manual. What does everyone else do? We have so few patients to base a critical value on, that it seems futile.

Would it make sense to do correlation between our lab values and the current reference lab values. Then if we correlate with their values, use their critical value as ours?

Hope this makes sense!

Thank you!

[ScottJM]

AABB has a nice booklet that we reference in our titer report to our hospital customers (in addition to what the TM has to say); Guidelines for Prenatal and Perinatal Immunohematology (ISBN 1-56395-208-4).

~Jeanne

[David Saikin]

The OB guys usually have their own idea of critical titers . . . it is more important, I think, to see that the titer and/or score is increasing. I have some prenatals with anti-K, or -E. Titers are 16 or higher BUT the "father" is negative for the ag so . . . they aren't doing any f/u titers. The abs are due to transfusions after the last pregnancy.

[swede]

The OB guys usually have their own idea of critical titers . . . it is more important, I think, to see that the titer and/or score is increasing. I have some prenatals with anti-K, or -E. Titers are 16 or higher BUT the "father" is negative for the ag so . . . they aren't doing any f/u titers. The abs are due to transfusions after the last pregnancy.

Yeah, That's what we keep telling the head of the Maternal/fetal clinic. He says we have to do our own studies and create our own critical titer based on patient and baby outcomes. We keep telling him that we follow AABB guidelines that were established from years of data. I am happy to hear that we are on the same page as everyone else.

[Malcolm Needs ☆]

The OB guys usually have their own idea of critical titers . . . it is more important, I think, to see that the titer and/or score is increasing. I have some prenatals with anti-K, or -E. Titers are 16 or higher BUT the "father" is negative for the ag so . . . they aren't doing any f/u titers. The abs are due to transfusions after the last pregnancy.

True, they probably are due to a previous transfusion, BUT, that does not mean that the K negative "father" is actually the real father. Sometimes women "play away", as well as men!We always genotype the foetus via maternal peripheral blood, just in case, unless the mother is ABSOLUTELY certain that the prospective father is the father (and we need that in writing from the hospital).Better to be safe than sorry!!!!!!!

[David Saikin]

We have to trust the mom to be straightforward with this one . . . the docs explain the critical nature of honesty in this instance. I guess we'll find out more at delivery . . .

Just as an aside, years ago I had a prenatal with anti-K. The mom was "shooting up" with the father's blood (some cult thing) . . . K+ DAT, sick baby.

[Deny Morlino]

Just as an aside, years ago I had a prenatal with anti-K. The mom was "shooting up" with the father's blood (some cult thing) . . . K+ DAT, sick baby.

WHAT!!! People are amazing!

[rravkin@aol.com]

Did you ask this doctor to explain how these studies should be done? I would be curious to know the practicle end of such studies. Maybe then he would agree with you and David.

Yeah, That's what we keep telling the head of the Maternal/fetal clinic. He says we have to do our own studies and create our own critical titer based on patient and baby outcomes. We keep telling him that we follow AABB guidelines that were established from years of data. I am happy to hear that we are on the same page as everyone else.

[swede]

Unfortunately this doctor only wants to send to his favorite lab, period. He wants us to have our own titer results compared to the outcome of his patients. He agreed that we would never have enough data of our own!

We will do correlations with the reference lab, find out their "critical titer" and then approach him again.

[rravkin@aol.com]

Hey Swede, let us know what happens.