Last week, I discussed genetic tests that aim to detect disorders in a foetus during pregnancy. This week, I look at pre-pregnancy or carrier tests. These tests are taken by couples that are considering having a baby, but are worried about the genetic disorders that they may pass on, possibly because there is a history of genetic disease in the family. The couple can then base their decision on how to go ahead with family planning on the test results.
There is an overlap between what pre-pregnancy tests do and the services offered by more traditional genetic counselors and clinical geneticists. In fact, most companies market their preconception tests via genetic clinics, rather than directly to consumers. Whether direct-to-consumer genetic tests should be legal at all is still being debated in many countries.
Two companies that develop sequencing-based preconception tests are Good Start Genetics and Ambry. Counsyl, another company in the sector, uses array-based technology. The number of disorders that can currently be detected with pre-pregnancy tests is higher than what is possible with non-invasive prenatal diagnosis. Whilst Sequenom's prenatal test returns information about a single disorder (trisomy 21), Good Start's test diagnoses 22 disorders, Counsyl's over 100, and Ambry's 90. But even once the providers of prenatal tests catch up, there is still the question if it makes sense to screen for less severe conditions. Do parents really want to know that their baby boy will suffer from pattern baldness once he grows up? The number of conditions that can be diagnosed is likely to be different from the number of conditions that are actionable.
But why stop at genetic counselling for couples? The start-up Gmatch plans to offer genotyping to the customers of an online dating website who want their future partner not only to be compatible socially, but to be a perfect genetic match as well.
Next week, I'll look at the third way besides prenatal and pre-pregancy diagnosis: Pre-implantation diagnosis.
January 27, 2012
January 21, 2012
The most prominent company offering prenatal diagnosis by screening is Sequenom. This week, Sequenom announced a public offering of shares valued in excess of $50m. The aim is to finance further expansion of its business, including sales of its MaterniT21 prenatal test.
The principle behind the MaterniT21 test is that some of the DNA in a pregnant woman's blood is of foetal origin. By sequencing that DNA, it is in principle possible to reconstruct most of the genotype of the foetus, and to detect most genetic disorders from the 10th week of pregnancy onwards- earlier than with equivalent tests.
Sequenom's MaterniT21 test currently only returns information on whether there is an third copy of chromosome 21, which causes Down syndrome. If the test returns a positive result, the parents can then decide which actions to take, which could include termination of the pregnancy.
Even at lower prices, which will probably be paid for by insurers anyway, the big question is how many couples are willing to purchase a test. Of 4.1 million births each year in the US, 750,000 (18%) are judged to be at a high risk of Down syndrome or other chromosomal abnormalities, either because the mother is over 35 years old or because there is a history of such disorders in the family.
It is likely that in the future the tests of Sequenom and its competitors will include other disorders such as cystic fibrosis, muscular dystrophy, anaemia, neuropsychiatric conditions like autism, and beta-thalassaemia. This could widen their appeal to parents that are not in the 18% currently judged as high risk. If prices come down sufficiently, I don't see a reason why sequencing-based tests for pregnant women could not be as prevalent as ultrasound is today.
At 4.1 million births in the US alone each year, and even if the price of tests decreases to a fraction of what they are now, it could well be a multi-billion dollar market.
Time to buy some of those new Sequenom shares?