Feature

Mass genetic screening: the mirage of choice

Calls are now being made for mass screening against genetic disorders. But screening offers no easy solutions, says Jane Jefferson

Researchers announced recently that they had found the gene for cystic fibrosis — the most common genetic disease in the Caucasian population. As the locations of more and more genes are identified, calls are being made increasingly for an extension to genetic screening programmes to prevent cystic fibrosis and other genetic disorders such as thalassaemia, Duchanne muscular dystrophy, sickle cell anaemia and Huntingdon’s disease.

Screening can take two forms: carrier or prenatal. Carrier screening is used to identify the people who have the gene for a ‘recessive’ condition. Carriers themselves have no ill-effects and probably do not know that they are carriers, but if the person they have children with is also a carrier, there is a one -in-four risk of the offspring suffering the disorder. Prenatal screening identifies those foetuses that have a genetic disease, so that the mother then has the choice of whether to continue with the pregnancy or not.

The provision of carrier-screening enables people who are carriers to avoid pairing-up with other carriers, or at least to prepare in advance for the issues they will face if they plan a pregnancy. Screening for many conditions is now quick and simple, requiring only a mouthwash to gather the necessary genetic material. However, population testing is expensive because of the numbers involved, and in addition to laboratory costs, there is a massive requirement for counselling, information and education, to ensure that communities and individuals understand the significance of their results.

Carrier screening can lead to fear and stigma for those identified as carriers even though they themselves are not ill. This has happened after some screening programmes, most notably in the case of sickle-cell trait in the US, where there have been reports of social and employment discrimination.

When prenatal screening becomes available, couples at risk of the disorder usually welcome the test. They may have experience of relatives’ suffering. Not surprisingly, calls for wider availability of screening often come from communities with a high incidence of a particular disorder — like thalassaemia in the Cypriot community. But the choice for many couples may be largely illusory.

To choose not to have the test, or having had a positive result, to choose not to terminate the pregnancy, may be almost impossible because of the guilt involved in knowing you could have prevented the birth of an affected child. Recriminations also come from families, communities and doctors. Although some women would welcome the opportunity to plan in advance for a child with potentially-severe disability, they report coming under pressure before screening takes place to agree to an abortion if the test is positive. This has even led to the case of one woman refused an abortion on social grounds being pressured to have one on medical grounds.