New DNA screening test can gauge risk of genetic diseases

If my parents knew before I was conceived that I would someday develop a chronic disease, would they still have had me? I wonder. I would have been spared the challenges of living with ulcerative colitis—diarrhea, rectal bleeding, abdominal pain, and weight loss. But then, I wouldn’t be here now.

The fact is, my parents did not know my chances of developping ulcerative colitis, a disease hypothesized to be heritable. They likely had never even heard of ulcerative colitis—no one in my family had had the disease until I came along. Without that knowledge, the thought of not having me may never have crossed their minds.

However, couples looking to start a family may soon be able to screen themselves for diseases that they could pass on to their children. News of the new screening procedure, which will begin trial use this fall in the U.S., was presented in a study published in the journal Science Translational Medicine.

After a sample of blood, hair, or skin is provided, the test scans a potential parent’s genome for rare recessive disease genes that can hide in their DNA.

We all carry two copies of almost all of our genes, one each from our mother and father. In the case of genetic illnesses, recessive genes from both the mother and father need to be present before the illness will develop. Parents with the same recessive disease genes run a one in four risk of passing the illness to their offspring.

The pre-conception carrier test is capable of screening several hundred DNA samples simultaneously for over 500 recessively inherited diseases.

Stephen Kingsome, lead author of the study and chief science officer at the U.S. National Center for Genome Resources, estimates that the cost of a single screening test would be around $500.

“On average, you or I or anybody in a North American population has two to three catastrophic disease mutations in their genome,” said Kingsmore. “If you are starting to have a family, this is the type of information you might want to know.”

Inherited childhood diseases are still uncommon in the general populace, but combined they account for roughly 20% of all infant deaths and 10% of all pediatric hospitalizations. Over the last few decades, over 1,000 genes involved in these diseases have been identified.

Although the study’s authors acknowledge that their data are preliminary, they note the apparently random distribution of two to three mutations in the general population as evidence that preconception screening should be made available for everyone.

Currently, in Canada only a few genetic illnesses are commonly screened for in couples prior to conception, and even then only for targetted high-risk populations. These include cystic fibrosis in northern European populations and Tay-Sachs disease in Ashkenazi Jewish populations.

Testing of the screening technology will begin at Kansas City’s Children’s Mercy Hospital over the next several months.

I don’t think my parents regret having me, at least not too much. But if a genetic screening test was available to them, and if they had an extra $500 kicking around, they may have been better prepared for my eventual diagnosis. Or maybe their adopted, colitis-free child would have written this article.

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