Noninvasive prenatal testing brings new options, opportunities, questions

Noninvasive prenatal testing is moving from bench to bedside at a dizzying pace, and while this rapid integration into clinical practice is raising important clinical and ethical questions, it also is creating exciting new opportunities – such as the potential for antenatal treatment of Down syndrome.

In an editorial in Prenatal Diagnosis, Dr. Lyn S. Chitty and Dr. Diana W. Bianchi note that "we are in the midst of a paradigm shift in the way that prenatal screening and diagnosis are performed around the world."

The shift is occurring at a pace unprecedented in the history of prenatal care, and the available tests, which measure cell free fetal DNA (cfDNA) in the maternal blood and currently are used to detect trisomy 21, 18, and 13, as well as sex chromosome aneuploidies, provide a "readily accessible and generally safer option for prenatal testing than can be offered from 10 until 40 weeks of gestation," wrote Dr. Chitty of Great Ormond Street and University College London hospitals and Dr. Bianchi, the Natalie V. Zucker Professor of Pediatrics, Obstetrics, and Gynecology of Tufts University, Boston (Prenatal Diagnosis 2013;33:511-13).

October will mark 2 years since the commercial debut of the first noninvasive prenatal test (NIPT) for aneuploidy in the United States – MaterniT21 (Sequenom, San Diego), a laboratory-developed test that detects increases in the amount of chromosomal 21, 18, and 13 material in maternal blood.

"This was followed by multiple publications, several professional society recommendations, and a logarithmic uptake in the number of tests ordered. The reason why noninvasive prenatal testing (NIPT) represents a paradigm shift is that it changes the algorithm of screening followed by invasive testing that has been in practice worldwide for the last 30 years," they said.

Rather than undergoing combined ultrasound screening and serum screening (the "combined test"), followed by more invasive chorionic villus sampling or amniocentesis to rule out aneuploidy for a positive combined test, more women now have the option of a simple blood test. The negative predictive value of NIPT is high, so fewer women are subjected to the invasive procedures, which increase the risk for miscarriage and other adverse outcomes.

The NIPT options are expanding quickly; since MaterniT21 became available, three other companies launched similar tests: Harmony (Ariosa Diagnostics, San Jose, Calif.), verifi (Verinata Health, Redwood City, Calif.), and – most recently – Panorama (Natera, San Carlos, Calif.).

None are approved by the Food and Drug Administration, but all are performed in Clinical Laboratory Improvement Amendments (CLIA)–approved laboratories as laboratory-developed tests.

The tests are typically administered any time after 10 weeks’. gestation because that is generally when an adequate amount of fetal DNA is present in the maternal serum, Dr. Bianchi, also a geneticist and executive director of the Mother Infant Research Institute at Tufts, explained during an NIPT symposium at the annual meeting of the American College of Obstetricians and Gynecologists in New Orleans.

Some of the tests use massively parallel sequencing, which can be used to "look at everything," including sex chromosome aneuploidies, although most laboratories use software that masks all but the results of interest. Other tests use more targeted sequencing to focus on the chromosomes of interest.

Studies suggest that NIPT is at least 99% accurate for detecting trisomy 21 and trisomy 18, and between 79% and 92% accurate for trisomy 13, with a false positive rate of less than 1% for each, according to a 2012 fact sheet developed by the National Coalition for Health Professional Education in Genetics and the National Society of Genetic Counselors.

Serum screening, by comparison, has an 80%-95% detection rate for trisomy 21 and trisomy 18, with false-positive rates of 3% -5%. The rates for trisomy 13 are uncertain, according to the fact sheet.

Most studies to date have included mainly women with singleton pregnancies at high risk of trisomy 21 due to advanced maternal age, an abnormal serum screen, a personal or family history of aneuploidy, or an abnormal ultrasound, and as a result most current recommendations support screening only in this population.

A December 2012 opinion from the American College of Obstetricians and Gynecologists Committee on Genetics and the Society for Maternal-Fetal Medicine Publications Committee, for example, notes that NIPT "offers tremendous potential as a screening tool for fetal aneuploidy," but that it should be offered, after pretest counseling, only to women with high-risk singleton pregnancies. Cell-free fetal DNA testing has not been sufficiently evaluated in those at low risk or with multiple gestations, the committee said (Obstet. Gynecol. 2012;120:1532-4).

In January 2013, the National Society of Genetic Counselors released a similar position statement (J. Genet. Counsel. 2013 [doi: 10.1007/s10897-012-9564-0]).

New evidence, however, suggests that NIPT also is feasible in low-risk pregnancies.

For example, two studies in the July issue of Ultrasound in Obstetrics and Gynecology indicate that both routine and contingent implementation of NIPT for first trimester trisomy screening are feasible.

In one of the studies, Dr. M.M. Gil of King’s College Hospital, London, and his colleagues demonstrated that in 1,005 singleton pregnancies, routine NIPT for trisomies 21, 18, and 13 at 10 weeks’ gestation had a lower false positive rate than did the combined test performed at 12 weeks (0.1% vs. 3.4%), although abnormal results required confirmation using invasive testing.

"This study has shown that routine screening for trisomies by cfDNA testing at 10 weeks is feasible, allowing diagnosis of aneuploidies and the option of pregnancy termination within the first trimester," the investigators concluded (Ultrasound Obstet. Gynecol. 2013;42:34-40).

In the second study, which involved women with singleton pregnancies who underwent screening between March 2006 and May 2012, Dr. K.H. Nicolaides, also of King’s College Hospital, London, and his colleagues demonstrated that effective first trimester screening for Down syndrome can be achieved – with a 98% detection rate and an invasive testing rate below 0.5% – using contingent screening (Ultrasound Obstet. Gynecol. 2013;42:41-50).

"The results demonstrate that in contingent screening, a detection rate of 98% in fetuses with trisomy 21, at an overall invasive testing rate less than 0.5%, could be achieved by offering the cfDNA test to about 36%, 21%, and 11% of cases identified by first-line screening using the combined test alone, using the combined test with the addition of serum placental growth factor and alpha-fetoprotein, and using the combined test with the addition of placental growth factor, alpha-fetoprotein, and ductus venosus pulsatility index for veins, respectively," they said. "Screening for trisomy 21 by cfDNA testing contingent on the results of an expanded combined test would retain the advantages of the current method of screening, but with a simultaneous major increase in detection rate and decrease in the rate of invasive testing," they concluded.

Data also suggest that NIPT can be used successfully in twin pregnancies, albeit with the caveat that deeper sequencing may be necessary in these pregnancies, Dr. Bianchi noted.

These findings suggest that even wider implementation of NIPT is likely, she said, adding that there are major concerns about such implementation – not the least of which is fitting adequate pre- and posttest counseling into busy practices.

"It is not straightforward – there are multiple issues that need to be discussed," she said.

Questions also remain about the performance of the tests in normal- vs. high-risk pregnancies, she said.

Recently, a Blue Cross Blue Shield Technology Evaluation Center report concluded that NIPT meets the company’s criteria for both normal- and high-risk pregnancies, Dr. Bianchi noted.

"We’ll be hearing more about this in the coming year. Everyone is looking for more data," she said.

The results thus far – with more than 100,000 tests performed – undoubtedly have been encouraging. Since the integration of these tests into clinical practice began, many medical centers already are witnessing significant declines in the number of invasive procedures being performed for aneuploidy, Dr. Bianchi said, noting that such procedures have decreased by 34% in the first year at Tufts Medical Center, where NIPT is routinely offered as an option to high-risk women, and as an alternative to invasive procedures in average-risk women who test positive on traditional screening. Invasive procedures are strongly encouraged in those with aneuploidy detected on NIPT.

As a result of these outcomes, every aspect of the current standard of care is being questioned, Dr. Chitty and Dr. Bianchi wrote in their editorial. "For example, do we still need to measure maternal serum biomarkers, and what is the place of nuchal translucency measurement?" they asked.

The use of NIPT and the rapid advances taking place in the field, also raise important ethical questions.

Even before Sequenom introduced the MaterniT21 test to the market, the ethical implications of NIPT were being weighed. In a 2009 paper, Dr. Antina de Jong of Maastricht (the Netherlands) University and colleagues noted that although the introduction of NIPT would have some "ethically favorable consequences," such as the absence of iatrogenic miscarriage resulting from a test, earlier reassurance of a healthy fetus, a longer period for decision-making and the possibility of an early abortion, "which may be physically and psychologically less burdening and ethically less problematic because of presumed lower mortal fetal status," the possibility that NIPT would eventually include testing for a broader scope of abnormalities complicates the ethical issues.

Notwithstanding the potential benefits with respect to earlier decision making, one concern is the "normalization and trivialization of early selective abortion," they said, adding that "more generalized use of noninvasive testing could facilitate selective terminations of pregnancy in a range of conditions hitherto not diagnosed prenatally and where the arguments for and against termination may not have received sufficient scrutiny."

Also, testing for a broader scope of abnormalities has important implications regarding informed consent, they said (Eur. J. Hum. Genet. 2009 [doi:10.1038/ejhg.2009.203]).

"Informed consent will become far more challenging – if attainable at all. Moreover, should [NIPT] testing become available for a wider range of disorders including late-onset disease, this may lead to the same ethical difficulties as with regard to wide range testing of newborns, in which the dominant view is that the child’s right not to know should be respected," the authors wrote. "It is difficult to see how this respect can be upheld when, after broadening prenatal testing, children will be born with a positive test result for a serious late-onset disease."

Another facet of NIPT that is rife with ethical implications is noninvasive fetal whole genome sequencing, which was shown in a recent proof-of-concept study to be possible using only parental DNA samples and plasma. That study is revisited from a clinical standpoint in an article published in the same issue of Prenatal Diagnosis along with the editorial by Dr. Chitty and Dr. Bianchi and a number of other related articles and studies. (To give readers an overview of "this rapidly changing field," both the June and July issues of the journal are dedicated to NIPT, said Dr. Bianchi, the journal’s editor-in-chief).

"If noninvasive determination of the entire fetal genomic sequence becomes clinically available, there will be a significant increase in the number of ethical issues that arise," Dr. Chitty and Dr. Bianchi noted.

"You can imagine, it’s hard enough now to counsel about serum screening results for Down syndrome. Imagine if you had to deal with the entire human genome. But it’s coming – it’s coming, so we have to figure out ... what’s to be communicated to expectant couples," Dr. Bianchi said, adding that she hopes much of the groundwork for dealing with these issues will be laid in adult and pediatric populations before they have to be considered for fetuses.

While these advances bring with them ethical concerns, they also open doors to exciting opportunities, she said.

"The challenge now is to translate this technology into practice that is accessible to all pregnant women and in an ethical way that preserves informed parental choice, while not increasing overall costs to the health care system," Dr. Chitty and Dr. Bianchi said.

Dr. Bianchi is chair of the clinical advisory board for Verinata Health Inc., and has received honorarium and research funding from the company. She is editor-in-chief of the Journal of Prenatal Diagnosis, and has received honorarium from the company. Dr. Nicolaides’ and Dr. Gil’s studies were funded by grants from the Fetal Medicine Foundation. Dr. de Jong’s research was supported by the Centre for Society and Genomics in the Netherlands, funded by the Netherlands Genomics Initiative, and the Netherlands Organisation for Scientific Research Zonmw Prevention Fund.

Noninvasive prenatal testing is moving from bench to bedside at a dizzying pace, and while this rapid integration into clinical practice is raising important clinical and ethical questions, it also is creating exciting new opportunities – such as the potential for antenatal treatment of Down syndrome.

In an editorial in Prenatal Diagnosis, Dr. Lyn S. Chitty and Dr. Diana W. Bianchi note that "we are in the midst of a paradigm shift in the way that prenatal screening and diagnosis are performed around the world."

The shift is occurring at a pace unprecedented in the history of prenatal care, and the available tests, which measure cell free fetal DNA (cfDNA) in the maternal blood and currently are used to detect trisomy 21, 18, and 13, as well as sex chromosome aneuploidies, provide a "readily accessible and generally safer option for prenatal testing than can be offered from 10 until 40 weeks of gestation," wrote Dr. Chitty of Great Ormond Street and University College London hospitals and Dr. Bianchi, the Natalie V. Zucker Professor of Pediatrics, Obstetrics, and Gynecology of Tufts University, Boston (Prenatal Diagnosis 2013;33:511-13).

October will mark 2 years since the commercial debut of the first noninvasive prenatal test (NIPT) for aneuploidy in the United States – MaterniT21 (Sequenom, San Diego), a laboratory-developed test that detects increases in the amount of chromosomal 21, 18, and 13 material in maternal blood.

"This was followed by multiple publications, several professional society recommendations, and a logarithmic uptake in the number of tests ordered. The reason why noninvasive prenatal testing (NIPT) represents a paradigm shift is that it changes the algorithm of screening followed by invasive testing that has been in practice worldwide for the last 30 years," they said.

Rather than undergoing combined ultrasound screening and serum screening (the "combined test"), followed by more invasive chorionic villus sampling or amniocentesis to rule out aneuploidy for a positive combined test, more women now have the option of a simple blood test. The negative predictive value of NIPT is high, so fewer women are subjected to the invasive procedures, which increase the risk for miscarriage and other adverse outcomes.

The NIPT options are expanding quickly; since MaterniT21 became available, three other companies launched similar tests: Harmony (Ariosa Diagnostics, San Jose, Calif.), verifi (Verinata Health, Redwood City, Calif.), and – most recently – Panorama (Natera, San Carlos, Calif.).

None are approved by the Food and Drug Administration, but all are performed in Clinical Laboratory Improvement Amendments (CLIA)–approved laboratories as laboratory-developed tests.

The tests are typically administered any time after 10 weeks’. gestation because that is generally when an adequate amount of fetal DNA is present in the maternal serum, Dr. Bianchi, also a geneticist and executive director of the Mother Infant Research Institute at Tufts, explained during an NIPT symposium at the annual meeting of the American College of Obstetricians and Gynecologists in New Orleans.

Some of the tests use massively parallel sequencing, which can be used to "look at everything," including sex chromosome aneuploidies, although most laboratories use software that masks all but the results of interest. Other tests use more targeted sequencing to focus on the chromosomes of interest.

Studies suggest that NIPT is at least 99% accurate for detecting trisomy 21 and trisomy 18, and between 79% and 92% accurate for trisomy 13, with a false positive rate of less than 1% for each, according to a 2012 fact sheet developed by the National Coalition for Health Professional Education in Genetics and the National Society of Genetic Counselors.

Serum screening, by comparison, has an 80%-95% detection rate for trisomy 21 and trisomy 18, with false-positive rates of 3% -5%. The rates for trisomy 13 are uncertain, according to the fact sheet.

Most studies to date have included mainly women with singleton pregnancies at high risk of trisomy 21 due to advanced maternal age, an abnormal serum screen, a personal or family history of aneuploidy, or an abnormal ultrasound, and as a result most current recommendations support screening only in this population.

A December 2012 opinion from the American College of Obstetricians and Gynecologists Committee on Genetics and the Society for Maternal-Fetal Medicine Publications Committee, for example, notes that NIPT "offers tremendous potential as a screening tool for fetal aneuploidy," but that it should be offered, after pretest counseling, only to women with high-risk singleton pregnancies. Cell-free fetal DNA testing has not been sufficiently evaluated in those at low risk or with multiple gestations, the committee said (Obstet. Gynecol. 2012;120:1532-4).

In January 2013, the National Society of Genetic Counselors released a similar position statement (J. Genet. Counsel. 2013 [doi: 10.1007/s10897-012-9564-0]).

New evidence, however, suggests that NIPT also is feasible in low-risk pregnancies.

For example, two studies in the July issue of Ultrasound in Obstetrics and Gynecology indicate that both routine and contingent implementation of NIPT for first trimester trisomy screening are feasible.

In one of the studies, Dr. M.M. Gil of King’s College Hospital, London, and his colleagues demonstrated that in 1,005 singleton pregnancies, routine NIPT for trisomies 21, 18, and 13 at 10 weeks’ gestation had a lower false positive rate than did the combined test performed at 12 weeks (0.1% vs. 3.4%), although abnormal results required confirmation using invasive testing.

"This study has shown that routine screening for trisomies by cfDNA testing at 10 weeks is feasible, allowing diagnosis of aneuploidies and the option of pregnancy termination within the first trimester," the investigators concluded (Ultrasound Obstet. Gynecol. 2013;42:34-40).

In the second study, which involved women with singleton pregnancies who underwent screening between March 2006 and May 2012, Dr. K.H. Nicolaides, also of King’s College Hospital, London, and his colleagues demonstrated that effective first trimester screening for Down syndrome can be achieved – with a 98% detection rate and an invasive testing rate below 0.5% – using contingent screening (Ultrasound Obstet. Gynecol. 2013;42:41-50).

"The results demonstrate that in contingent screening, a detection rate of 98% in fetuses with trisomy 21, at an overall invasive testing rate less than 0.5%, could be achieved by offering the cfDNA test to about 36%, 21%, and 11% of cases identified by first-line screening using the combined test alone, using the combined test with the addition of serum placental growth factor and alpha-fetoprotein, and using the combined test with the addition of placental growth factor, alpha-fetoprotein, and ductus venosus pulsatility index for veins, respectively," they said. "Screening for trisomy 21 by cfDNA testing contingent on the results of an expanded combined test would retain the advantages of the current method of screening, but with a simultaneous major increase in detection rate and decrease in the rate of invasive testing," they concluded.

Data also suggest that NIPT can be used successfully in twin pregnancies, albeit with the caveat that deeper sequencing may be necessary in these pregnancies, Dr. Bianchi noted.

These findings suggest that even wider implementation of NIPT is likely, she said, adding that there are major concerns about such implementation – not the least of which is fitting adequate pre- and posttest counseling into busy practices.

"It is not straightforward – there are multiple issues that need to be discussed," she said.

Questions also remain about the performance of the tests in normal- vs. high-risk pregnancies, she said.

Recently, a Blue Cross Blue Shield Technology Evaluation Center report concluded that NIPT meets the company’s criteria for both normal- and high-risk pregnancies, Dr. Bianchi noted.

"We’ll be hearing more about this in the coming year. Everyone is looking for more data," she said.

The results thus far – with more than 100,000 tests performed – undoubtedly have been encouraging. Since the integration of these tests into clinical practice began, many medical centers already are witnessing significant declines in the number of invasive procedures being performed for aneuploidy, Dr. Bianchi said, noting that such procedures have decreased by 34% in the first year at Tufts Medical Center, where NIPT is routinely offered as an option to high-risk women, and as an alternative to invasive procedures in average-risk women who test positive on traditional screening. Invasive procedures are strongly encouraged in those with aneuploidy detected on NIPT.

As a result of these outcomes, every aspect of the current standard of care is being questioned, Dr. Chitty and Dr. Bianchi wrote in their editorial. "For example, do we still need to measure maternal serum biomarkers, and what is the place of nuchal translucency measurement?" they asked.

The use of NIPT and the rapid advances taking place in the field, also raise important ethical questions.

Even before Sequenom introduced the MaterniT21 test to the market, the ethical implications of NIPT were being weighed. In a 2009 paper, Dr. Antina de Jong of Maastricht (the Netherlands) University and colleagues noted that although the introduction of NIPT would have some "ethically favorable consequences," such as the absence of iatrogenic miscarriage resulting from a test, earlier reassurance of a healthy fetus, a longer period for decision-making and the possibility of an early abortion, "which may be physically and psychologically less burdening and ethically less problematic because of presumed lower mortal fetal status," the possibility that NIPT would eventually include testing for a broader scope of abnormalities complicates the ethical issues.

Notwithstanding the potential benefits with respect to earlier decision making, one concern is the "normalization and trivialization of early selective abortion," they said, adding that "more generalized use of noninvasive testing could facilitate selective terminations of pregnancy in a range of conditions hitherto not diagnosed prenatally and where the arguments for and against termination may not have received sufficient scrutiny."

Also, testing for a broader scope of abnormalities has important implications regarding informed consent, they said (Eur. J. Hum. Genet. 2009 [doi:10.1038/ejhg.2009.203]).

"Informed consent will become far more challenging – if attainable at all. Moreover, should [NIPT] testing become available for a wider range of disorders including late-onset disease, this may lead to the same ethical difficulties as with regard to wide range testing of newborns, in which the dominant view is that the child’s right not to know should be respected," the authors wrote. "It is difficult to see how this respect can be upheld when, after broadening prenatal testing, children will be born with a positive test result for a serious late-onset disease."

Another facet of NIPT that is rife with ethical implications is noninvasive fetal whole genome sequencing, which was shown in a recent proof-of-concept study to be possible using only parental DNA samples and plasma. That study is revisited from a clinical standpoint in an article published in the same issue of Prenatal Diagnosis along with the editorial by Dr. Chitty and Dr. Bianchi and a number of other related articles and studies. (To give readers an overview of "this rapidly changing field," both the June and July issues of the journal are dedicated to NIPT, said Dr. Bianchi, the journal’s editor-in-chief).

"If noninvasive determination of the entire fetal genomic sequence becomes clinically available, there will be a significant increase in the number of ethical issues that arise," Dr. Chitty and Dr. Bianchi noted.

"You can imagine, it’s hard enough now to counsel about serum screening results for Down syndrome. Imagine if you had to deal with the entire human genome. But it’s coming – it’s coming, so we have to figure out ... what’s to be communicated to expectant couples," Dr. Bianchi said, adding that she hopes much of the groundwork for dealing with these issues will be laid in adult and pediatric populations before they have to be considered for fetuses.

While these advances bring with them ethical concerns, they also open doors to exciting opportunities, she said.

"The challenge now is to translate this technology into practice that is accessible to all pregnant women and in an ethical way that preserves informed parental choice, while not increasing overall costs to the health care system," Dr. Chitty and Dr. Bianchi said.

Dr. Bianchi is chair of the clinical advisory board for Verinata Health Inc., and has received honorarium and research funding from the company. She is editor-in-chief of the Journal of Prenatal Diagnosis, and has received honorarium from the company. Dr. Nicolaides’ and Dr. Gil’s studies were funded by grants from the Fetal Medicine Foundation. Dr. de Jong’s research was supported by the Centre for Society and Genomics in the Netherlands, funded by the Netherlands Genomics Initiative, and the Netherlands Organisation for Scientific Research Zonmw Prevention Fund.

Noninvasive prenatal testing is moving from bench to bedside at a dizzying pace, and while this rapid integration into clinical practice is raising important clinical and ethical questions, it also is creating exciting new opportunities – such as the potential for antenatal treatment of Down syndrome.

In an editorial in Prenatal Diagnosis, Dr. Lyn S. Chitty and Dr. Diana W. Bianchi note that "we are in the midst of a paradigm shift in the way that prenatal screening and diagnosis are performed around the world."

The shift is occurring at a pace unprecedented in the history of prenatal care, and the available tests, which measure cell free fetal DNA (cfDNA) in the maternal blood and currently are used to detect trisomy 21, 18, and 13, as well as sex chromosome aneuploidies, provide a "readily accessible and generally safer option for prenatal testing than can be offered from 10 until 40 weeks of gestation," wrote Dr. Chitty of Great Ormond Street and University College London hospitals and Dr. Bianchi, the Natalie V. Zucker Professor of Pediatrics, Obstetrics, and Gynecology of Tufts University, Boston (Prenatal Diagnosis 2013;33:511-13).

October will mark 2 years since the commercial debut of the first noninvasive prenatal test (NIPT) for aneuploidy in the United States – MaterniT21 (Sequenom, San Diego), a laboratory-developed test that detects increases in the amount of chromosomal 21, 18, and 13 material in maternal blood.

"This was followed by multiple publications, several professional society recommendations, and a logarithmic uptake in the number of tests ordered. The reason why noninvasive prenatal testing (NIPT) represents a paradigm shift is that it changes the algorithm of screening followed by invasive testing that has been in practice worldwide for the last 30 years," they said.

Rather than undergoing combined ultrasound screening and serum screening (the "combined test"), followed by more invasive chorionic villus sampling or amniocentesis to rule out aneuploidy for a positive combined test, more women now have the option of a simple blood test. The negative predictive value of NIPT is high, so fewer women are subjected to the invasive procedures, which increase the risk for miscarriage and other adverse outcomes.

The NIPT options are expanding quickly; since MaterniT21 became available, three other companies launched similar tests: Harmony (Ariosa Diagnostics, San Jose, Calif.), verifi (Verinata Health, Redwood City, Calif.), and – most recently – Panorama (Natera, San Carlos, Calif.).

None are approved by the Food and Drug Administration, but all are performed in Clinical Laboratory Improvement Amendments (CLIA)–approved laboratories as laboratory-developed tests.

The tests are typically administered any time after 10 weeks’. gestation because that is generally when an adequate amount of fetal DNA is present in the maternal serum, Dr. Bianchi, also a geneticist and executive director of the Mother Infant Research Institute at Tufts, explained during an NIPT symposium at the annual meeting of the American College of Obstetricians and Gynecologists in New Orleans.

Some of the tests use massively parallel sequencing, which can be used to "look at everything," including sex chromosome aneuploidies, although most laboratories use software that masks all but the results of interest. Other tests use more targeted sequencing to focus on the chromosomes of interest.

Studies suggest that NIPT is at least 99% accurate for detecting trisomy 21 and trisomy 18, and between 79% and 92% accurate for trisomy 13, with a false positive rate of less than 1% for each, according to a 2012 fact sheet developed by the National Coalition for Health Professional Education in Genetics and the National Society of Genetic Counselors.

Serum screening, by comparison, has an 80%-95% detection rate for trisomy 21 and trisomy 18, with false-positive rates of 3% -5%. The rates for trisomy 13 are uncertain, according to the fact sheet.

Most studies to date have included mainly women with singleton pregnancies at high risk of trisomy 21 due to advanced maternal age, an abnormal serum screen, a personal or family history of aneuploidy, or an abnormal ultrasound, and as a result most current recommendations support screening only in this population.

A December 2012 opinion from the American College of Obstetricians and Gynecologists Committee on Genetics and the Society for Maternal-Fetal Medicine Publications Committee, for example, notes that NIPT "offers tremendous potential as a screening tool for fetal aneuploidy," but that it should be offered, after pretest counseling, only to women with high-risk singleton pregnancies. Cell-free fetal DNA testing has not been sufficiently evaluated in those at low risk or with multiple gestations, the committee said (Obstet. Gynecol. 2012;120:1532-4).

In January 2013, the National Society of Genetic Counselors released a similar position statement (J. Genet. Counsel. 2013 [doi: 10.1007/s10897-012-9564-0]).

New evidence, however, suggests that NIPT also is feasible in low-risk pregnancies.

For example, two studies in the July issue of Ultrasound in Obstetrics and Gynecology indicate that both routine and contingent implementation of NIPT for first trimester trisomy screening are feasible.

In one of the studies, Dr. M.M. Gil of King’s College Hospital, London, and his colleagues demonstrated that in 1,005 singleton pregnancies, routine NIPT for trisomies 21, 18, and 13 at 10 weeks’ gestation had a lower false positive rate than did the combined test performed at 12 weeks (0.1% vs. 3.4%), although abnormal results required confirmation using invasive testing.

"This study has shown that routine screening for trisomies by cfDNA testing at 10 weeks is feasible, allowing diagnosis of aneuploidies and the option of pregnancy termination within the first trimester," the investigators concluded (Ultrasound Obstet. Gynecol. 2013;42:34-40).

In the second study, which involved women with singleton pregnancies who underwent screening between March 2006 and May 2012, Dr. K.H. Nicolaides, also of King’s College Hospital, London, and his colleagues demonstrated that effective first trimester screening for Down syndrome can be achieved – with a 98% detection rate and an invasive testing rate below 0.5% – using contingent screening (Ultrasound Obstet. Gynecol. 2013;42:41-50).

"The results demonstrate that in contingent screening, a detection rate of 98% in fetuses with trisomy 21, at an overall invasive testing rate less than 0.5%, could be achieved by offering the cfDNA test to about 36%, 21%, and 11% of cases identified by first-line screening using the combined test alone, using the combined test with the addition of serum placental growth factor and alpha-fetoprotein, and using the combined test with the addition of placental growth factor, alpha-fetoprotein, and ductus venosus pulsatility index for veins, respectively," they said. "Screening for trisomy 21 by cfDNA testing contingent on the results of an expanded combined test would retain the advantages of the current method of screening, but with a simultaneous major increase in detection rate and decrease in the rate of invasive testing," they concluded.

Data also suggest that NIPT can be used successfully in twin pregnancies, albeit with the caveat that deeper sequencing may be necessary in these pregnancies, Dr. Bianchi noted.

These findings suggest that even wider implementation of NIPT is likely, she said, adding that there are major concerns about such implementation – not the least of which is fitting adequate pre- and posttest counseling into busy practices.

"It is not straightforward – there are multiple issues that need to be discussed," she said.

Questions also remain about the performance of the tests in normal- vs. high-risk pregnancies, she said.

Recently, a Blue Cross Blue Shield Technology Evaluation Center report concluded that NIPT meets the company’s criteria for both normal- and high-risk pregnancies, Dr. Bianchi noted.

"We’ll be hearing more about this in the coming year. Everyone is looking for more data," she said.

The results thus far – with more than 100,000 tests performed – undoubtedly have been encouraging. Since the integration of these tests into clinical practice began, many medical centers already are witnessing significant declines in the number of invasive procedures being performed for aneuploidy, Dr. Bianchi said, noting that such procedures have decreased by 34% in the first year at Tufts Medical Center, where NIPT is routinely offered as an option to high-risk women, and as an alternative to invasive procedures in average-risk women who test positive on traditional screening. Invasive procedures are strongly encouraged in those with aneuploidy detected on NIPT.

As a result of these outcomes, every aspect of the current standard of care is being questioned, Dr. Chitty and Dr. Bianchi wrote in their editorial. "For example, do we still need to measure maternal serum biomarkers, and what is the place of nuchal translucency measurement?" they asked.

The use of NIPT and the rapid advances taking place in the field, also raise important ethical questions.

Even before Sequenom introduced the MaterniT21 test to the market, the ethical implications of NIPT were being weighed. In a 2009 paper, Dr. Antina de Jong of Maastricht (the Netherlands) University and colleagues noted that although the introduction of NIPT would have some "ethically favorable consequences," such as the absence of iatrogenic miscarriage resulting from a test, earlier reassurance of a healthy fetus, a longer period for decision-making and the possibility of an early abortion, "which may be physically and psychologically less burdening and ethically less problematic because of presumed lower mortal fetal status," the possibility that NIPT would eventually include testing for a broader scope of abnormalities complicates the ethical issues.

Notwithstanding the potential benefits with respect to earlier decision making, one concern is the "normalization and trivialization of early selective abortion," they said, adding that "more generalized use of noninvasive testing could facilitate selective terminations of pregnancy in a range of conditions hitherto not diagnosed prenatally and where the arguments for and against termination may not have received sufficient scrutiny."

Also, testing for a broader scope of abnormalities has important implications regarding informed consent, they said (Eur. J. Hum. Genet. 2009 [doi:10.1038/ejhg.2009.203]).

"Informed consent will become far more challenging – if attainable at all. Moreover, should [NIPT] testing become available for a wider range of disorders including late-onset disease, this may lead to the same ethical difficulties as with regard to wide range testing of newborns, in which the dominant view is that the child’s right not to know should be respected," the authors wrote. "It is difficult to see how this respect can be upheld when, after broadening prenatal testing, children will be born with a positive test result for a serious late-onset disease."

Another facet of NIPT that is rife with ethical implications is noninvasive fetal whole genome sequencing, which was shown in a recent proof-of-concept study to be possible using only parental DNA samples and plasma. That study is revisited from a clinical standpoint in an article published in the same issue of Prenatal Diagnosis along with the editorial by Dr. Chitty and Dr. Bianchi and a number of other related articles and studies. (To give readers an overview of "this rapidly changing field," both the June and July issues of the journal are dedicated to NIPT, said Dr. Bianchi, the journal’s editor-in-chief).

"If noninvasive determination of the entire fetal genomic sequence becomes clinically available, there will be a significant increase in the number of ethical issues that arise," Dr. Chitty and Dr. Bianchi noted.

"You can imagine, it’s hard enough now to counsel about serum screening results for Down syndrome. Imagine if you had to deal with the entire human genome. But it’s coming – it’s coming, so we have to figure out ... what’s to be communicated to expectant couples," Dr. Bianchi said, adding that she hopes much of the groundwork for dealing with these issues will be laid in adult and pediatric populations before they have to be considered for fetuses.

While these advances bring with them ethical concerns, they also open doors to exciting opportunities, she said.

"The challenge now is to translate this technology into practice that is accessible to all pregnant women and in an ethical way that preserves informed parental choice, while not increasing overall costs to the health care system," Dr. Chitty and Dr. Bianchi said.

Dr. Bianchi is chair of the clinical advisory board for Verinata Health Inc., and has received honorarium and research funding from the company. She is editor-in-chief of the Journal of Prenatal Diagnosis, and has received honorarium from the company. Dr. Nicolaides’ and Dr. Gil’s studies were funded by grants from the Fetal Medicine Foundation. Dr. de Jong’s research was supported by the Centre for Society and Genomics in the Netherlands, funded by the Netherlands Genomics Initiative, and the Netherlands Organisation for Scientific Research Zonmw Prevention Fund.