NEW YORK -- It's important to offer patients a range of options for trisomy 21 screening, Dr. Fergal D. Malone said at an obstetrics symposium sponsored by Columbia University and New York Presbyterian Hospital.
The screening options that women choose will vary depending upon their perceived risk for having a child with Down syndrome. "Some want the highest detection rate, while others want the lowest false-positive rate. No one size fits all," said Dr. Malone, director of obstetric and gynecologic ultrasound and director of perinatal research at Columbia Presbyterian Medical Center.
At his institution, women are offered one of two screens for trisomy 21. They can choose first-trimester combined screening, in which nuchal translucency (NT), pregnancy-associated plasma protein A (PAPP-A), and free [beta]-human chorionic gonadotropin (hCG) are measured at 10-14 weeks and the results are provided. If the results are positive, chorionic villus sampling (CVS) is then offered.
Alternatively, a patient can opt for integrated screening, in which NT and PAPP-A are measured at 10-14 weeks, followed by the quad screen (serum alpha fetoprotein, hCG, unconjugated estriol, and inhibin A) at 15-16 weeks, and the results are given all at once as a single risk value; if the results are positive, amniocentesis is then offered to the patient.
In general, the integrated screen is optimal if speed is not a priority, while the first-trimester combined screen is better if speed is important, Dr. Malone said.
Overall, 85% of Columbia patients choose the integrated screen, while only 15% of women choose the first-trimester combination with the option of CVS. However, 90% of the women who choose the first-trimester combined screen are age 37 or older, while just 30% of those choosing integrated screening are in that age group.
It appears, then, that patients who perceive themselves to be at high risk for Down syndrome are more likely to choose an early test with early results. On the other hand, those who believe their risk is low tend to select the test with the lowest possible false-positive rate, which they perceive to be the most efficient, he said.
Interestingly, 88% of the women who had negative first-trimester screens decided to undergo amniocentesis anyway, while 60% of those with positive first-trimester screens refused a CVS and then waited until the second trimester to undergo amniocentesis.
It may be that many women of advanced maternal age already have decided that they will undergo an invasive test no matter what the results of their screening test are, and are using the first-trimester screen merely to determine whether their risk is high enough to go with CVS--which they perceive as more dangerous--or to wait for the "safer" test, amniocentesis.
Women with a positive first-trimester screen who refuse CVS may not feel the result was "bad enough" to justify the procedure, Dr. Malone speculated.
But regardless of their reasons. "There's a range of patients out there who want different things from their screening tests. We need to position ourselves over the next few months and years to be able to offer them a range of screening tests," he said.
BY MIRIAM E. TUCKER
COPYRIGHT 2004 International Medical News Group
COPYRIGHT 2004 Gale Group