Safe Test for Down Syndrome and Other Genetic Disorders

During a pregnancy common prenatal testing is performed invasive or non-invasive (methods), diagnosis for diseases or conditions in fetus (embryo) before birth. 1 "According to the March of Dimes, about 150,000 babies are born with birth defects each year (2007) in the United States". One of many causes related to a birth defect one missing or faulty gene ("Genes are the things that determine physical traits - how we look - and lots of other stuff about us." Inherited from generations within families" 3) within a chromosome (contains genetic information 4). The human body has about 25,000 genes that predetermine specific characteristics before we are born. 2 Healthy and normal number of chromosomes in a fetus (Euploid) forty-six. "The chromosomes come in pairs and numbered based on their size." 6 Less than or more than normal number of chromosomes (Aneuploidy) frequently referred to as cytogenetic abnormality. 5 An extra or missing chromosome attributed to cause a genetic disorder called Down syndrome (Most cases attributed to an extra chromosome also called Trisomy 21 8): Lower than average cognitive ability and mild to moderate developmental disabilities. 7 Also, approximately half of all Down syndrome children have hearing and vision problems. 8 "The incidence of Down syndrome is estimated at 1 per 800 to 1,000 births, although these statistics are heavily influenced by the age of the mother (Women older than 35 years increase the risk of a higher probability 8). 7 Theorizing as woman gets older chromosomes in the egg are less likely to divide normally leading to the egg having an extra or missing chromosome. 6 "Other factors may also play a role." 7

Amniocentesis is an invasive prenatal diagnostic test, performed between fourteen weeks and usually up to about twenty weeks during a pregnancy: Evaluate if the baby has a birth defect or genetic disorder including Down syndrome. 1 During the procedure a fine needle is inserted into the placenta (sac surrounding the fetus 9) guiding by ultrasound to remove a sample of the amniotic fluid. In a laboratory the amniotic fluid is tested for genetic risks including Down syndrome (checking for the number and size of chromosomes 11) and sex of the baby. 10 Amniocentesis does involve a certain degree of risk for a miscarriage (about 1 in 400 or 2 to 4 in 400 studies). 11 Studies suggest the risk of miscarriage during Amniocentesis is greater during the later stage of a pregnancy. Women older than 35 years are more likely to be tested for chromosome disorders. 12 If Down syndrome or other genetic disorder is diagnosis during the early stage of the pregnancy more options are considered regarding this situation and parents could have more time to prepare themselves through counseling for child born with a health problem. Also, other invasive tests evaluate the health of the fetus but incur a risk for a miscarriage. 1

Published in Proceedings of the National Academy of Science (PNAS) on October 6, 2008, researcher Stephen R. Quake (Howard Hughes Medical Institute) and colleagues at Stanford University developed a new type of blood test which scan fetal DNA in a mother's blood, evaluating if the fetus cells contains extra chromosomes associated to severe birth defects (such as Edward syndrome and Patau syndrome linked to infant mortality 13) including Down syndrome. The new blood test compared to amniocentesis provides test results within a couple of days rather than having to wait two or three weeks. Also, the new test outweighs up to one percent risk of a miscarriage during amniocentesis. The new blood test utilizes gene sequencing technology ("DNA sequencing , the process of determining the exact order of the 3 billion chemical building blocks that make up the DNA of the 24 different human chromosomes..." 15) and application of sophisticated computer analyze of a sample of blood. During a research study of eighteen pregnant women, the new blood test confirmed amniocentesis test results 14: Nine women with Down syndrome pregnancies and the three other pregnancies different chromosomal disorders. According to Stephen Quake a larger test among pregnant women is necessary, further verify the efficacy of the new blood test which is hoped will be available for routine prenatal testing of a baby's health within two or three years. 13 During the next phase of testing estimated cost per test will be approximately $300. 14 According to Stephen Quake, Stanford University is in negotiations to license the new technology to a company. 16

Sequenom a biotechnology company in San Diego California will begin selling in June 2009 a blood test like the one Stephen Quake and colleagues have developed as a non-invasive blood test to diagnosis pre-birth chromosome genetic disorders. When the Sequenom blood test becomes available will require detection of a genetic disorder confirmed by amniocentesis or chronic villus sampling (C.V.S.) of the amniotic fluid. "But Harry Styli, chief executive of Sequenom, said that if the test is accurate enough, "it will ultimately replace amnio and C.V.S." According to Sequenom stated to have patent rights regarding their blood test as a defensive objective that will block Stanford University and other competitors. Dr. Styli estimates Sequenom's test insurance companies will pay $600 - $800 compared to the projected list price of $2,000. 16

References:

1.) Prenatal diagnosis - http://en.wikipedia.org/wiki/Prenatal_testing

2.) Birth Defects -

http://kidshealth.org/parent/pregnancy_newborn/medical_problems/birth_defects.html

3.) What is a Gene? - http://kidshealth.org/kid/talk/qa/what_is_gene.html

4.) Chromosome - http://www.healthline.com/galecontent/chromosome-1

5.) Aneuploidy and Deletions - http://arbl.cvmbs.colostate.edu/hbooks/genetics/medgen/chromo/aneuploidy.html

6.) What is Aneuploidy - http://www.reproductivegenetics.com/aneuploidy.html

7.) Down Syndrome - http://en.wikipedia.org/wiki/Down_syndrome

8.) Down Syndrome - http://kidshealth.org/parent/medical/genetic/down_syndrome.html

9.) placenta - http://www.answers.com/topic/placenta

10.) Pregnancy and Amniocentesis - http://www.webmd.com/baby/guide/amniocentesis

11.) Amniocentesis - http://www.webmd.com/baby/amniocentesis-17766

12.) Amniocentesis- http://www.marchofdimes.com/professionals/14332_1164.asp

13.) New non - invasive prenatal blood test for Down's syndrome, safer for the fetus - http://www.news-medical.net/?id=41874

14.) New blood test for Down syndrome - http://www.physorg.com/news142565133.html

15.) Fact About Genome Sequencing - http://www.ornl.gov/sci/techresources/Human_Genome/faq/seqfacts.shtml

16.) Blood Tests Ease Search for Down syndrome - http://www.blueridgenow.com/article/20081007/znyt04/810070306&tc=yahoo