Prenatal Testing

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Dr. Josh Copel:  “This is Josh Copel for OBGYN.net, and I’ve managed to find Beryl Benacerraf as she’s leaving for the plane to ask her a question submitted by e-mail.  Beryl, the question here is when we use markers in trisomy 21 during the second trimester and when nuchal translucency during the first trimester and triple screen markers are normal, can we consider these markers to be independent?  Can we use a Bayes theorem approach to create a new maternal risk after the first tests that are different from the maternal second trimester age related risks?”

Dr. Beryl Benacerraf:  “Actually, I don’t know the answer to that question.  I think there is a study going on right now in the United States, which is trying to answer that question, but I think that it’s possible that we can lower that risk.  I think the markers in the first trimester and the markers in the second trimester, and particularly, the ultrasound markers are probably independent of each other, other than the nuchal fold.  Probably the best approach is to use both gestational ages instead of markers in order to have a complete assessment of the risk.”

Dr. Josh Copel:  “The question sounds very much like the paper by Nick Wald in the New England Journal of Medicine over the summer of 1999 which made the assumption that all the markers were independent but we can’t assume that till it’s been studied such as in the study that you’ve just mentioned.  Wouldn’t you agree?”

Dr. Beryl Benacerraf:  “Yes, I agree.  I think the study that I’ve just mentioned whose name escapes me right now but…”

Dr. Josh Copel:  “It’s either the FASTER Trial or the FIRST Trial.”

Dr. Beryl Benacerraf: “Yes, the FASTER Trial, I think that will be a very important study for a lot of different reasons.  It may change the way that we approach prenatal screening for chromosomal abnormalities in the future.”

Dr. Josh Copel:  “Thank you.”