First-Trimester Screening Works Well in Clinics


RENO, NEV. — First-trimester aneuploidy screening is practical not just in the context of clinical trials but also in the everyday world of the clinic, according to a poster presented by Sriram C. Perni, M.D., and colleagues at the annual meeting of the Society for Maternal-Fetal Medicine.

Among 2,515 women evaluated at a single institution, trisomy 21 was detected in 91% of 22 pregnancies when the false-positive rate was set to 5% and in 77% of 22 pregnancies when the false-positive rate was set to 1%.

In that same group, trisomy 18 was detected in all eight affected pregnancies, whether the false-positive rate was set to 5% or 1%.

Aneuploidy screening in the first trimester relies on an algorithm incorporating four pieces of data: maternal age, blood levels of pregnancy-associated plasma protein A (PAPP-A), blood levels of free β-human chorionic gonadotrophin (free β-hCG), and ultrasound measurements of fetal nuchal translucency, Dr. Perni said.

A large, multicenter, clinical trial involving 8,514 patients found this algorithm to have a good sensitivity and an acceptable false-positive rate (N. Engl. J. Med. 2003;349:1405-13).

But it remained unclear whether the algorithm would perform as well in the real-world setting of a single institution, reported Dr. Perni and his colleagues at Weill Medical College of Cornell University, New York.

At their clinic, 4,883 pregnant women, who together had 5,167 fetuses, were offered first-trimester aneuploidy screening, and 2,515 women agreed.

Of those pregnancies, there were a total of 37 aneuploid fetuses—1 with trisomy 13, 8 with trisomy 18, 22 with trisomy 21, 4 with 45X, 1 with 47XXY, and 1 with triploidy.

Of the 22 cases of trisomy 21, 3 resulted in a live birth, and 19 were electively terminated. All eight fetuses with trisomy 18 were electively terminated.

Asked in an interview whether first-trimester aneuploidy screening remained controversial, Dr. Perni replied, “I don't think it's controversial, but right now it's not the standard of care. There needs to be more evidence that it's reproducible at a single institution like this.

“This is a very, very good test,” continued Dr. Perni, who disclaimed any financial interest in the test.

“It can be done very early and has a very good detection rate for fixed false-positive rates,” he said.

He said that many insurance carriers in New York City do cover the screening test. And while the test has become “almost the standard of care” in certain parts of the United States, “it just hasn't become vogue over the whole country.”

He added, “I think the most exciting thing about this is that we can get information for couples and women specifically very early on to help them determine what they want to do.”

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