Knowing a baby’s whole genetic code would help detect a range of health problems, but would not replace need for some existing tests
What is the current newborn screening?
All babies in the UK are offered the “heel prick” or blood spot test at around five days old to screen for nine serious health conditions, including cystic fibrosis, sickle cell disease and various metabolic diseases. These conditions, if identified, can be treated or managed. Genetic testing is only offered in certain cases, such as if there is a concern that the baby might be at risk of an inherited disorder.
What is whole-genome sequencing?
Whole-genome sequencing (WGS) reads out the entire DNA code. It is already being used in the NHS to diagnose rare diseases and could be used to screen for mutations that are linked to a wider range of treatable serious diseases that affect babies. Genomics England says that using WGS could allow the current nine conditions screened for to be expanded to more than 200. Genetic data can also be used to predict a person’s risk of adulthood diseases, such as Alzheimer’s and heart disease.
Do other countries offer whole-genome sequencing?
No. There have been pilot studies for whole-genome sequencing for newborn screening, including a trial at Boston Children’s hospital, in which about 7% of families took up the offer. There are also countries that screen for a larger number of childhood diseases using an expanded panel of biochemical and targeted gene tests.
Is this the only approach?
Geneticists are in agreement that the UK’s newborn screening should be upgraded. Whole-genome sequencing is one way of achieving this. Another option would be to enhance the existing screening using a panel of genetic tests designed to detect mutations on specific genes. Some argue that these tests would be cheaper, and potentially more accurate for certain conditions.
Are there advantages to WGS?
A key advantage is flexibility: new conditions could be added to the screening list relatively easily since data for the entire genome is already being collected. Such a large dataset of genomic and linked health records would also allow scientists to learn more about genetic predictors of health and disease and potentially help develop new treatments. Some say that genomics will inevitably play an increasingly important role in healthcare and argue that it will be an advantage for participants, and the UK, to be at the forefront of this development.
What are the downsides?
Whole-genome sequencing can be less efficient at predicting some conditions than biochemical tests. This means that WGS would need to be combined with the existing screening process, rather than replacing it. There are also some conditions that are not currently screened for, such as spinal muscular atrophy, which may be detected more readily using a targeted gene test, optimised to pick up certain mutations.
WGS allows scientists to screen for mutations in an almost unlimited number of genes, but screening genes that are less well understood can create a risk of false positives. When genetic mutations of unknown significance are discovered, it can create a diagnostic grey zone. Whole-genome sequencing is also expensive – roughly £1,000 per genome once analysis and data storage is accounted for. Based on this estimate, it would cost around £700m to sequence all newborns annually.
There are also significant ethical questions about the consent process for collecting whole-genome data, which can be used to predict health outcomes in adulthood, and questions about who owns this data and how access to it is determined.