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Safe Prenatal Genetic Test?

What are the methods of prenatal diagnosis? There are two groups: invasive and non-invasive techniques:

  • Non-invasive methods:
    • examination of the uterus from outside the body (see Leopold’s Maneuvers)
    • ultrasound technique (like the 4D ultrasound)
    • AFP screening
    • Detection of fetal blood cells that have made their way into the mother’s bloodstream, so we can obtain a sample of the baby’s DNA.
  • Invasive methods:

Obviously, the aim is to develop a method which is

  • safe (some invasive tests pose a risk to the pregnancy)
  • sensitive (ultrasound detection may suffer from a high rate of false negatives and false positives)
  • cheap (you know our modern world very well)
  • non-invasive

According to the BBC article, now, scientists are trying to create a non-invase blood test by examining samples of foetal DNA present in the mother’s blood for variations in the sequence of the genetic material. These variations are known as single nucleotide polymorphisms (SNPs).

The Ravgen team, led by Ravinder Dhallan, has been able to maximise the amount of DNA that can be recovered by treating the blood samples with a chemical called formaldehyde.

Ravinder Dhallan, a doctor and researcher, founded Ravgen (Rapid analysis of variations in a genome) in 2000 with the goal of solving major clinical problems. The key to early diagnosis and improved treatment lies in separating relevant, disease-associated genetic signals from the background of non disease-associated signals.

What could be the benefits of that new method according to Alexandra Benachi and Jean-Marc Costa (the Lancet)?

  • Being able to identify genetic abnormalities at an early stage not only gives parents the chance to decide whether or not to proceed with the pregnancy, but also alerts medical staff to the need for close monitoring right through to birth.
  • They were also able to determine whether the foetus was carrying extra copies of key chromosomes which cause genetic disease such as Down syndrome or Klinefelter syndrome.
  • An accurate non-invasive test would mean a lot women with normal babies would not have to be put through a procedure like amniocentesis.

Although, if I want to be neutral, I should list the other side’s concerns:

  • The amount of free foetal DNA in maternal blood is low, and although the use of formaldehyde allows an increased amount to be isolated from maternal blood, yields are irregular.
  • Only eight women have been assessed in the first trimester – further testing in this stage of pregnancy will be essential.


Thank you Darmok for the suggestions!

15 Comments Post a comment
  1. sciencesque #

    Great post!. My wife and I were just talking about this last night. In Alberta, Canada, they are talking about increasing the number of women who get their babies screen for genetic abnormalities. As it stands now, only women over 35 have access to amnios due to the increased risk of Downs syndrome, etc. Unfortunately, amnios come with some risk (1-2% chance of miscarriage, I believe). If more women start getting amnios even though they are not in a high risk group for genetic abnormalities, then I imagine the number of miscarriages will also needlessly increase. If this non-invasive testing works, that would be great. But unfortunately, more benefits of genetic testing would be realized if the tests were done earlier rather than later in the pregnancy. Perhaps the technique will improve.

    February 2, 2007
  2. You’re right. The chance of miscarriage is 0,25-0,5% in amniocentesis, 0.5 to 1 %in CVS. But you should note that aminocentesis is only done in women with higher risks. And yes, an early, non-invasive test would be much needed.

    I’ll follow the improvements of this test and will let you know if something important happens…

    February 2, 2007
  3. And if you want to avoid plagiarism, you should use quotation marks and attribute the quotations the Lancet editorialists rather than presenting it as your own writing.

    February 4, 2007
  4. It’s not easy to plagiarise if you don’t even read that article. :) I used only the BBC page. BTW, you mean I plagiarised the list of the other side’s concerns?

    February 4, 2007
  5. The sentences you used were quoted directly in the BBC article. It would be highly improbably that you invented them independently. Yes, you used lines from the editorial by Alexandra Benachi and Jean-Marc Costa.

    February 4, 2007
  6. If you mean the list of concerns, now it’s a quotation. But the others are not. Anyway somewhy you don’t like me. :) Are you satisfied with the post now?

    February 4, 2007
  7. It is not sufficient to simply place copied text in quotation marks; the one who is the source of the quotation must be specified.

    I don’t know you well enough to like you or dislike you. But I find your blog fascinating, which is why I read it critically.

    February 4, 2007
  8. OK then, maybe I’m too sensitive these days. The group of methods and the obvious aims are mine. In the next short paragraph I link to te exact source. Then I talk about the Ravgen team (with information from their homepage), and the last two lists are made by the already sourced BBC article.

    Thank you for your critics! Sometimes I argue with them, but they’re important to improve my blogging skills. So keep it up!

    February 4, 2007
  9. I’m sorry that I wasn’t clear. If you read the BBC article, you will see that those statements are quotations from Alexandra Benachi and Jean-Marc Costa; it is your failing to mention them as the ones who originally made the statements that I object to. The BBC quoted those statements from their longer editorial.

    I apologize if my manner is overly brusque. But please be assured that it is only because I read your blog so carefully that I could even notice this sort of discrepancy.

    February 4, 2007
  10. I hope that it’s correct now. Anyway, don’t care about your style, just bomb me with these suggestions, they always help me to improve.

    February 4, 2007
  11. Well—you seem to be doing just fine!

    February 5, 2007
  12. Can you explain to me what this MyBlogLog thing is?

    February 5, 2007
  13. MyBlogLog is a community for bloggers. You can join other bloggers’ communities, you can watch who links to you… And with that widget, you can log your readers by name and picture (those who are registered in MyBlogLog).

    February 5, 2007

Trackbacks & Pingbacks

  1. Genetics and Health » We Love Genetics… We Love Genetics Not
  2. New Clues For Down Syndrome? « ScienceRoll

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