Achilles heals: new era of newborn screening
Newborn screening for cystic fibrosis was added to the existing heel-prick test in Ireland for the first time last Friday. This is brilliant news as it will enable early detection and treatment leading to enhanced quality of life for many newborns. Ireland was one of the first countries to implement a national newborn screening programme and cystic fibrosis is the first disease to be added permanently to it in 32 years. With this in mind I wondered why the current diseases are being tested and how screening might evolve in the near future.
Ireland screens for six different diseases and each of these has severe symptoms in absence of early treatment. Other countries include different diseases on their newborn screening programme. Our nearest neighbours, UK, does not screen for three of the six diseases on the Irish programme: homocystinuria, galactosemia and maple syrup urine disease. These diseases have higher than average incidence in Ireland.
Galactosemia, for instance, is the failure of the body to breakdown galactose, a sugar in human and cow’s milk. It is at its highest frequency in the world (1 in 450 births) in babies born to Irish Traveller parents. In contrast, in the non-traveller Irish community this drops to 1 in 36,000. This shows that the study of genetic changes in populations is an important factor when considering diseases for inclusion in screening programmes.
Cystic fibrosis has only been added to the heel-prick test now despite Ireland having the highest incidence in the world so perhaps there are other diseases that should be included. A study in the United States developed criteria to evaluate diseases for inclusion in newborn screening programmes. These criteria included the incidence, the burden of the untreated disease and the screening test. Medium-chain acyl-CoA dehydrogenase deficiency, a condition which prevents the body from converting some fats into energy, was the top ranking disease for inclusion. In the United States, this disease is more common among individuals of northern European ancestry. This is currently not part of the Irish heel-prick test but was included in the UK’s test in 2009.
Another factor to consider is that increasing population diversity over the past number of years may change incidence of certain diseases in Ireland. One such disease, sickle-cell anaemia has high incidence in Sub-Saharan Africa due to its survival advantage in carriers (people with one abnormal gene) against malaria. In Nigeria, the disease is so prevalent that 1 in 50 babies are born with it. Early diagnosis and care reduces the disease symptoms and risk of childhood death. Already included in national screening in many other countries, this could be a candidate for inclusion in the Irish heel-prick test in the near future.
New technology may help with the inclusion of these diseases as well as many more. Tandem mass spectrometry enables simultaneous testing of multiple conditions using the same blood sample. For instance, the newborn screening programme in the province of Ontario in Canada started using this method in 2006 and now screens 25 conditions in their heel-prick test. Expanded screening in Ireland is currently under consideration.
The addition of cystic fibrosis last Friday will hopefully herald the beginning of a new future of newborn screening in Ireland. A simple heel-prick could soon prevent a huge array of diseases from becoming burdensome or even fatal. The heel will symbolise improved health rather than fatal weakness!
American College of Medical Genetics Newborn Screening Expert Group (2006). Newborn Screening: Toward a Uniform Screening Panel and System–Executive Summary. PEDIATRICS 2006;117:S296-S307. PEDIATRICS, 118 (2), 851-851 DOI: 10.1542/peds.2006-1566
Heel-prick image: Eric T. Sheler / Wikipedia