Genetic test detects inherited diseases

Scientists have created “a genetic test that allows couples to be checked for incurable inherited diseases before they think about starting a family”, the Daily Mail has reported.

The research behind this story is a genetics study that has combined relevant scientific methods to allow potential parents’ DNA to be screened for 448 serious genetic conditions. The results point to a feasible screening test that could indicate the risk that a couple’s offspring will inherit a serious genetic disease. However, this was established in a research setting and there is further work to be done. For example, the list of diseases assessed needs refining, the testing process needs automating and appropriate reporting and counselling methods still have to be developed. Most importantly, the test itself requires testing in a real-world setting.

Furthermore, there are a number of ethical, legal and social implications that would need to be carefully and sensitively considered before this type of multi-purpose genetic screening can be implemented. Crucially, any system in which the test is offered would need to provide supportive counselling for couples alongside the test, enabling them to make sense of the results and make informed decisions based on them.

Gene testing

The researchers say that although single gene disorders are individually rare, collectively they account for about 20% of infant mortality and about 10% of hospitalisations in children. The researchers report that there have been reductions in the incidences of some diseases such as cystic fibrosis and Tay-Sachs disease since preconception screening and genetic counselling has been offered to couples in the US.

The researchers in this study developed a method to screen couples for a range of genes that might cause severe recessive childhood disorders in their children if they were to conceive. Recessive genetic disorders occur when a person carries two faulty copies of a particular gene – one inherited from each parent. If a person possesses only one faulty copy of a gene they will not be affected by a recessive condition, but will be a “carrier”. If two carriers of a particular faulty gene have a child there will be:

* a one-in-four chance that their child will inherit two copies of the recessive gene and therefore have the related condition
* a one-in-two chance that their child will only inherit a single faulty gene and therefore be unaffected, but a carrier
* a one-in-four chance that their child will not inherit any copies of the faulty gene, and therefore will not be affected or a carrier

The researchers report that 1,138 of the genes that cause recessive diseases have been identified, but that preconception testing in the USA is recommended only for five of them, including cystic fibrosis and Tay-Sachs disease.