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DNA testing techniques prompt wider debate

Posted in Diagnostic testing, Scientific research by Matt at WelcometoIllinois on October 29, 2008

I wrote yesterday about the importance of accuracy in ante-natal testing for chromosome abnormalities such as Down’s syndrome, noting that I am in favour of new non-invasive DNA testing currently being developed.

On the subject of those DNA testing procedures I previously wrote that “While the development of more accurate testing procedures is to be welcomed in terms of reducing false-positives and false-negatives, I believe they also provide an opportunity for wider debate on the accepted wisdom that it is acceptable to prenatally diagnose Down’s syndrome in the first place.”

It is in that context that this article in the Washington Post makes for interesting reading, covering as it does a new DNA test called comparative genomic hybridization that uses “‘microarrays’ or gene chips to search for dozens of less common, often more severe syndromes caused by subtle deletions or additions of genetic material that standard genetic analysis misses.”

As the article indicates, the development of this technique, which can detect about 150 known genetic disorders, raises both hope and concern:

Some worry that the technique could be used to hunt for the rapidly growing list of genetic markers that merely signal an increased risk for cancer, diabetes, mental illness, obesity, addiction and other conditions later in life. Someday, similar tests could perhaps even vet fetuses for traits associated with beauty, personality or intelligence.

It is easy to dismiss such concerns as exaggeration. Less so the fact that the tests are already being promoted by two labs – the report mentions Baylor College of Medicine and Signature Genomic Laboratories – before a a $3.3m federally funded study evaluating the technology in 4,000 pregnancies led by  Ronald J. Wapner of Columbia University, has been completed.

Then there is the fact that the results do not necessarily provide parents with enough information for them to make an informed decision. The report quotes Leslie G. Biesecker of the federal government’s National Human Genome Research Institute:

“There’s a lot of variation down in the DNA that as far as anyone knows today not only doesn’t cause any disease or syndrome, but doesn’t have any consequence whatsoever. They are part of what make us different,” Biesecker said. “The trick is, you have to distinguish whether it’s going to cause any disorder. We’re not there yet.”

Even if the abnormalities detected are in a region of DNA clearly associated with a known syndrome, it is often unclear how severely affected the child would be. Missing DNA almost always causes a syndrome. But extra DNA in the same area may or may not, or may cause a mild version. Many of the syndromes can range from devastating to barely noticeable.

“We’re opening up a huge can of worms,” said Caroline Ogilvie of the Guy’s and St. Thomas’ NHS Foundation Trust in London. “More information is not always a good thing.”

“Put yourself in the place of a woman who is carrying a baby she wants,” said Jan Friedman of the University of British Columbia. “You find something that may or may not be abnormal. If it’s abnormal it may be very bad, or it may be normal. She doesn’t know what to do about it. If she continues a pregnancy, it may be a serious abnormality. If she terminates a pregnancy, she may be terminating a normal baby.”

While I am not naive enough to believe that society can reverse the trend towards increased ante-natal screening I still think there is room for debate about why it is done. Ironically it is the development of easier and more broadly-applicable tests that provides the best hope that the debate will take place.


3 Responses

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  1. […] Is screening for Down’s syndrome ethical? That is the central question that I believe should be at the heart of the debate I would like to see as more accurate and less-invasive testing procedures become available. […]

  2. […] use of DNA chips in diagnostic testing I previously wrote about the use of “‘microarrays’ or gene chips in the genetic testing process and a new DNA […]

  3. […] However, the story is pretty much a re-hash of the issues discussed in this article in the same paper in October 2006, which I covered here. […]

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