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More accurate Down syndrome screening test hits the market
Article first published online: 21 DEC 2011
Copyright © 2011 Wiley Periodicals, Inc.
American Journal of Medical Genetics Part A
Volume 158A, Issue 1, pages viii–ix, January 2012
How to Cite
(2012), More accurate Down syndrome screening test hits the market. Am. J. Med. Genet., 158A: viii–ix. doi: 10.1002/ajmg.a.35199
- Issue published online: 19 DEC 2011
- Article first published online: 21 DEC 2011
Obstetricians applaud safety but question value, advocates urge proper counseling
San Diego-based Sequenom is marketing its MaterniT21 test, now available in 20 metropolitan areas, as an adjunct to current screening for high-risk patients including women of advanced maternal age and those who have a family history of DS, an ultrasound finding suggestive of a fetal chromosome abnormality, or unusual results on other biochemical screening tests. The test is accurate as early as 10 weeks of gestation, and the company recommends its use in conjunction with other testing modalities, such as targeted ultrasound. The test also covers trisomies 18 and 13.
Sequenom will report trisomy 21 results in twin pregnancies. The company will also report on chromosome 21 mosaicism if relevant samples have sufficient fetal DNA to allow detection, says Allan T. Bombard, MD, Sequenom's Chief Medical Officer and Clinical Professor of Obstetrics and Gynecology at the University of California, San Diego.
Dr. Bombard says Sequenom intends to seek approval from the U.S. Food and Drug Administration for a similar version of the test. Meanwhile, both Verinata Health and Gene Security Network reportedly intend to soon market their own noninvasive DS screening tests that use fetal DNA circulating in maternal blood.
A research version of Sequenom's test is quite accurate, according to a study in the November 2011 Genetics in Medicine. Funded by Sequenom and led by Brown University's Jacob Canick, PhD, investigators at 27 international sites compared fetal karyotyping with Sequenom's test in 212 DS and 1,484 matched, normal pregnancies. The test detected 98.6% of the DS pregnancies with a false positive rate of just 0.2% (Palomaki et al., 2011).
The paper did not include data on trisomies 13 and 18, but the researchers will publish sensitivity and specificity figures for these conditions in a separate paper, Dr. Bombard says.
Cost, Access, and Utility
The American College of Obstetrics and Gynecology (ACOG) will issue an opinion on new noninvasive prenatal screening for DS and other trisomies sometime after January 2012, says W. Allen Hogge, MD, Chair of ACOG's Committee on Genetics and the University of Pittsburgh's Department of Obstetrics, Gynecology and Reproductive Services. An ACOG recommendation means insurers are more likely to cover the $1,900 test. Currently, Sequenom is offering it at a maximum of $235 out of pocket to patients who have insurance coverage for it, Dr. Bombard says.
While he would not divulge ACOG's official opinion, Dr. Hogge questions the Sequenom test's utility. While it is more precise and has fewer false positives than current screening methods, it is far more expensive, doesn't add much useful information, and adds another step to the screening process at roughly the same cost as a diagnostic test, he says.
The test could also delay DS diagnosis, he adds. Obstetricians don't start current screening until 11 weeks, and receipt of results from Sequenom will take 8 to 10 days, according to the company, which suggests ultrasound as well. Patients who get positive results on this test, therefore, may miss the opportunity for early diagnostic testing by chorionic villus sampling, Dr. Hogge says.
Discussions with Patients
Obstetricians should counsel women about the test prior to giving it, says Brian Skotko, MD, Clinical Genetics Fellow at Children's Hospital Boston. Women need clear explanations of the purpose and limits of the test, how it's done, when results are available, how results are delivered, and the meaning of positive and negative results, he says. They also need to be told that the test isn't 100% accurate, he adds.
Giving adequate pre-test counseling or delivering positive results for the Sequenom test may be a challenge for obstetricians, the majority of whom have never met a person with DS, and many others who aren't aware of advances in care, education, and quality of life. According to a 2009 survey of 507 ACOG fellows, more than 40% thought their training related to DS was “less than adequate” (Driscoll et al., 2009).
As a result of this lack of knowledge, couples with DS pregnancies may get inaccurate and unduly negative information about DS from uninformed obstetricians and even genetics professionals unaware of remarkable advances made in the last 30 years, Dr. Skotko says.
The quality of life for people with Down syndrome and their families is usually quite good, say subjects of surveys of people with DS, their parents, and siblings by a research team that includes Dr. Skotko. In one survey, researchers found an overwhelming majority of parents are happy with their decisions to have their children with DS, express love and pride for them, and report these children have good relationships with their siblings. In a separate survey of siblings, a large majority describes their relationship with siblings with DS as positive. Nearly all respondents to a third survey of people with DS age 12 and older say they live happy, fulfilling lives (Skotko et al., 2011a, b, c).
Dr. Skotko points out that the National Down Syndrome Society (NDSS) recommends that obstetricians delivering positive results and geneticists who see couples with DS pregnancies offer the booklet “Understanding Down Syndrome Diagnosis” within 24 hours of a positive diagnosis. Jointly created by organizations representing healthcare professionals and families, the booklet covers available health and education services, common medical conditions for babies with DS, information about pregnancy options, and helpful resources.
Parents as Experts
Families that include children with DS are the best people to educate expectant couples about what their lives are like, says Betsy Goodwin, NDSS founder and board member. While Goodwin urges physicians to deliver DS diagnoses with sensitivity, preferably with both parents present, she says connecting parents with advocacy groups and opportunities to educate themselves is even more important.
If possible, expectant parents and healthcare professionals should attend one of 300 NDSS “Buddy Walks” held across the nation each year, Goodwin says. The events promote acceptance and inclusion of people with DS and are a great opportunity to talk to parents and meet children who aren't as disabled as many uninformed people imagine, she says.
“Recognize that what parents decide is their business, but they shouldn't decide in a vacuum,” Goodwin says. “How this experience goes is in the doctor's hands. Remember, you're talking about a baby.”
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