The integrated test is a new method of screening for Down's syndrome, which uses measurements obtained during the first and second trimesters of pregnancy to provide a single estimate of the risk of having a pregnancy with Down's syndrome.
The integrated test is safer and more effective than currently used tests, because high detection rates can be achieved with much lower false-positive rates than existing tests, as illustrated below.
For example, using the integrated test in place of the triple test, the detection rate is higher (86% compared with 77%), and the false-positive rate is much lower (1% compared with 5%).
The screening performance of each test was based on results in the SURUSS study and Wald NJ, Rodeck C, Hackshaw AK, Rudnicka AR (2004). SURUSS in perspective. Br J Obstet Gynaecol 111, 521-531
| Triple test | Maternal age with AFP, uE3 and total hCG in the second trimester |
| Quadruple test | Maternal age with AFP, uE3, total hCG and inhibin-A in the second trimester |
| Combined test | Maternal age with nuchal translucency, PAPP-A and hCG in the first trimester |
| Integrated test | Maternal age with nuchal translucency and PAPP-A in the first trimester, and AFP, uE3, total hCG and inhibin-A in the second trimester |
| Serum Integrated test | Maternal age with PAPP-A in the first trimester, and AFP, uE3, total hCG and inhibin-A in the second trimester |
For more information on the integrated test, see: Wald NJ, Watt HC, Hackshaw AK (1999) Integrated screening for Down's syndrome based on tests performed during the first and second trimesters. N Engl J Med 341, 461-467
alpha version 7.0 is the first screening software to interpret integrated test screening results. If you are interested in using alpha with the integrated test, please contact us.
Combining the ultrasound marker nuchal translucency with biochemical markers has been shown to be an effective method of screening for Down's syndrome in the first trimester of pregnancy (10-13 weeks) with an expected detection rate of 85% at a false-positive rate of 5%. (Wald NJ, Hackshaw AK. (1997) Combining ultrasound and biochemistry in first-trimester screening for Down's syndrome. Prenat Diagn 17, 821-829)
With alpha, you can interpret first trimester screening results as well as second trimester, using one software. You can also use alpha to interpret the integrated test, in which first and second trimester
Smith-Lemli-Opitz Syndrome (SLOS)
alpha version 7.0 can identify pregnancies at high risk of Smith-Lemli-Opitz syndrome (SLOS) among women who screen positive for Down's syndrome or Edward's syndrome (trisomy 18). An additional diagnostic test (measurement of 7-DHC in amniotic fluid) can then be offered to these women. This approach can detect 50-60% of SLOS pregnancies, without increasing the number of diagnostic tests performed.
Advances in second trimester screening
| In vitro fertilization | Second trimester
total hCG and free beta hCG levels are raised in women who have become
pregnant through in vitro fertilization(IVF) and
uE3 levels are low The screen positive rate in Down's syndrome
screening is correspondingly high; about double the rate in non-IVF
pregnancies.
(Wald
NJ, White N, Morris JK, Huttly WJ, Canick JA (1999) Serum markers for Down's syndrome in women who have had
in vitro
fertilization: implications for antenatal screening. Br J Obstet
Gynaecol 106, 1304-1306).
In IVF pregnancies, hCG and uE3 levels should be adjusted to avoid the high screen positive rate. |
| Inhibin-A | Adding
inhibin-A as a fourth marker to the standard triple
test increases the detection rate from 69% to 76% for a false-positive
rate of 5%. (Wald
NJ, Densem JW, George L, Muttukrishna S, Knight PG. (1996) Prenatal screening for Down's syndrome using
Inhibin-A as a serum
marker. Prenat Diagn 16, 143-153)
The inhibin-A based quadruple test has been shown to be the most effective second trimester screening test for Down's syndrome suitable for routine use. If you are involved in screening in the United States, and are interested in using inhibin-A in your screening programme, you can get more information from Jack Canick (jcanick@smtp.wihri.org) or Lenny Kellner (afpplus3@aol.com) |
| 14 weeks | The markers used
in screening for Down's syndrome between 15 and 22 weeks have now been
shown to be effective at 14 weeks. (Wald
NJ, Watt HC, Haddow JE, Knight GJ. (1998) Screening for Down syndrome at 14 weeks of pregnancy.
Prenat Diagn
18, 291-293)
It is reasonable to offer Down's syndrome screening using these markers from 14 weeks, although the serum AFP measurement for NTD screening is less effective at this time than between 16 and 18 weeks. |
Validating risk estimates using alpha Outcome
How do you know that the risk estimates generated by Down's syndrome screening software are accurate? The ability to demonstrate that risk estimates are correct would be a complete validation of the screening methodology.
alpha has been validated in this way, and only alpha (in conjunction with alpha Outcome) enables users to perform this validation analysis for themselves.
For more information on validating screening using alpha Outcome click here.
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STUDY DAYS FOR MIDWIVES |
Screening for
Down's syndrome
Wolfson Institute of Preventive Medicine A one day course, primarily aimed at midwives, nurses and health visitors involved in Down's syndrome screening, as well as antenatal screening coordinators and counsellors. The course provides theoretical and practical knowledge on all aspects of first and second trimester screening for Down's syndrome, with emphasis on education and patient counselling. Topics include:
For further details, please contact the course organiser, Cecily Cromby Email: Cecily
Cromby
Website: http://www.wolfson.qmul.ac.uk/epm/screening/midwife.html |
| COURSE | Intensive
course on screening for Down's syndrome
Wolfson Institute of Preventive
Medicine 9th - 11th May 2011 This is the fifteenth annual course to be held at the Wolfson Institute. Lasting three days, it is an intensive theoretical and practical course in antenatal screening for Down's syndrome. Topics covered include:-
For further details, please contact the course organiser: Email:
Cecily Cromby
Website: http://www.wolfson.qmul.ac.uk/epm/screening/intensive.html |
Serum, urine and ultrasound screening study (SURUSS)
The report of a large collaborative study designed to identify the most effective, safe and cost-effective method of antenatal screening for Down's syndrome, using nuchal translucency, first and second trimester serum and urine markers, and age, in various combinations. Results were based on about 47,000 pregnancies, including 101 pregnancies with Down' syndrome.
The full report, executive summary and editorial are available on the Journal of Medical Screening website free of charge. Click on the PDF to download the section required in PDF format.
You can also obtain the full report and the executive summary from the website of the NCCHTA (National Coordinating Centre for Health Technology Assessment). Click on Browse a list of all published HTA reports, select Search Publications, enter SURUSS in the search box, and Press Go. Click on the title of the report for details.
An international society set up in November 2002 to provide a forum for those interested in medical screening to discuss ideas and problems, and to share their experiences. The Journal of Medical Screening is the journal of the Society.
If you are interested in joining the Society, please visit their website
alpha achieves European and Canadian Quality Assurance
Approval
In December 2003, Logical Medical Systems was awarded a Certificate of
Approval by Lloyd's Register Quality Assurance, confirming its compliance
with the quality management system standards in ISO 9001:2000, ISO
13485:2003 and ISO 13485:1996.
alpha now carries a CE mark, in
accordance with the requirements of the European Directive on in-vitro
medical devices (Directive 98/79/EC) and the UK Medical Device
Regulations 2002:618.
Logical Medical Systems has also been approved for the development, distribution, installation, support and maintenance of software for antenatal risk evaluation under the relevant requirements of the Canadian Medical Devices Regulations.
Antenatal and Neonatal Screening - second edition
Edited by Nicholas Wald and Ian Leck
An up-to-date text on antenatal and neonatal screening, including chapters
on screening for neural tube defects and Down's syndrome, and on the
principles of screening using single-marker and multiple-marker tests.
For more details, or to order a copy, visit the OUP website
ISBN: 0-19-262826-7
Oxford University Press, November 2000
Oxford University Press
Tel: +44 (0)1536 454534
The following publications may be of interest. The references identify certain topics, such as the integrated test, the use of inhibin-A, validation of risk estimates, and detection of Smith-Lemli-Opitz syndrome. If you would like any further information, please let us know.
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©Logical Medical Systems
2006