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A new non-invasive test that examines foetal DNA can pick up genetic abnormalities such as Down's syndrome, researchers said today. Unlike more intrusive tests that may raise the risk of miscarriage, the new diagnostic tool developed by the US company Ravgen poses no threat to the mother or foetus.
It uses foetal DNA extracted from blood samples taken from the mother to screen for chromosomal abnormalities. In a preliminary study of 60 pregnant women reported online by The Lancet medical journal the test produced promising results.
''Right now in the market there is no test available that can reliably do what we do in this study which is, without needing any invasive procedure, to determine whether a baby has an abnormality or not,'' said Ravinder Dhallan, lead author of the study and the head of Ravgen.
The blood test correctly diagnosed Down's syndrome, one of the most common genetic abnormalities, in two cases. It also produced a false positive and a false negative.
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Let your genes become your diet expert
Let your genes become your diet expert
You do not need to make sudden changes in your diet any more because of any hereditary disease. Nutrogenomics, the latest buzzword in the field of health sciences, can help you have your own personalised diet in accordance with the genetic makeup of your body.
Health expert Dr. Sam Rehnborg, the president of Nutrilite Health Institute, California, says that now one doesn't have to go through the depression of making a sudden change in diet because of hereditary diseases like ailments of the heart or diabetes.
Today, the genetic makeup of a person can be easily determined, leading to detection of genes which can cause certain diseases. Nutrogenomics deals with the same concept of determining a person's genetic makeup and then charting out the diet accordingly, to lower the risks of those diseases.
Other than determining the genetic constitution of a person, nutrogenomics requires a person to give such details as his age, sex, eating habits and his lifestyle for a better diagnosis of a pre-determined problem.
According to Rehnborg, one in every four Indians will suffer from diseases of the heart in another decade. "Lack of exercise, bizarre eating habits, less sleep...our lifestyle is such that we simply invite trouble. Nutrogenomics will hence help in avoiding grave situations," he said
Already available in the US, this technique will come to India in a few years time.
Down's Syndrome occurs when a baby inherits three copies of chromosome 21 instead of two. The risk of having a Down's baby increases with maternal age.
Dhallan said the test can be adapted to look for abnormalities in any chromosome or single gene disorders.
''In this paper we show proof of principle of how this technology works,'' he said.
Women 35 years and older have been advised to have genetic testing for Down's syndrome and other disorders. But recently the American College of Obstetricians and Gynaecologists has recommended that all women be given the option of having genetic testing.
Standard tests to detect Down's syndrome include chorionic villus sampling (CVS) and amniocentesis. CVS, which is performed in the first 13 weeks of pregnancy, analyses placenta cells to detect any genetic abnormalities.
Amniocentesis is usually done at about 16 weeks and involves inserting a needle to withdraw a small amount of amniotic fluid.
The new test detects genetic abnormalities in the foetus by looking at single nucleotide polymorphisms, or SNPs, which are tiny variations in DNA.
Dhallan said he envisions the new test being used along with other tests. Results are available in two to four days.
In a commentary in The Lancet, French doctors said the results are encouraging but larger studies need to be done.
''Dhallan's test is promising and opens a new era in prenatal diagnosis but to be optimally used as a routine prenatal screening or diagnostic test, their findings need to be replicated in a large-scale multicentre setting,'' said Alexandra Benachi, of the Hospital Necker-Enfants Malades in Paris and Jean-Marc Costa, of the American Hospital of Paris.
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