09 November 2009
ByAppeared in BioNews 533
The UK National Screening Committee is considering plans to genetically screen newborn babies for a greater number of rare conditions. Currently, on a newborn's fifth day, a single spot of blood is taken from their heel, and they are screened for five conditions including sickle-cell disorders (SCD) and cystic fibrosis (CF). Parents then receive the results of the tests around eight weeks later. This lags behind some areas of Europe where they test for 10 or more conditions, and some American states that screen for up to 50.
Advocates of the new plans point out that it could result in children receiving earlier treatment for many serious conditions, possibly saving their lives, but many experts warn of downsides. For example, no test is perfect and so enlarging the screening process could mean that some parents are told that their child has one of these conditions when they do not. Millions more may be unnecessarily concerned about the chance of their child having one of these rare conditions, that can affect as few as four people in every million.
Every baby in England is currently tested for phenylketonuria (PKU), congenital hypothyroidism (CHT), SCD, CF and MCADD (Medium Chain Acyl-CoA Dehydrogenase Deficiency), under the newborn screening programme, although some areas also screen for other conditions. These five conditions each affect between one in 2,500 and one in 10,000 babies in the UK and were chosen for the screening programme because if caught early enough they are all treatable to some extent. PKU is an inherited condition which prevents the proper processing of a substance called phenylalanine in food, and if left untreated it causes serious, irreversible mental disability. Babies with CHT do not have enough of the hormone thyroxine, without which they do not grow properly and can develop permanent physical and mental disability. SCD are inherited disorders that can cause red blood cells to change to a sickle shape and get stuck in small blood vessels, causing pain and damage, serious infection, or even death. CF is an inherited condition that can affect the digestion and lungs, often causing babies to have frequent chest infections and problems gaining weight. Lastly, MCADD causes problems breaking down fats to make energy for the body, which can lead to serious illness and death.
A further eight conditions may now be added to the newborn bloodspot screening programme including Maple syrup urine disease, Isovaleric acidaemia, Glutaric aciduria type 1, Tyrosinaemia, Homocysteinuira, Congential adrenal hyperplasia, Biliary atresia and Pompe Disease. Many of these illnesses are life-threatening and they are all extremely rare - Pompe Disease affects fewer than 100 people in Britain. The screening committee will base their decision on a number of factors including what treatments are available for each condition, and how robust the screening tests are. 'We are considering all factors extremely carefully,' said Anne Mackie, the director of programmes for the UK National Screening Committee, adding: 'We recognise that this can be a frightening process for parents and we do not want to worry them unnecessarily without being sure that we can offer some treatment.'
'If you want to do newborn screening on all babies then the quality of the test has to be improved,' said Marita Pohlschmidt, from the Muscular Dystrophy Campaign which offers suppoert to those with Pompe Disease, adding: 'At the moment we would back screening only those in a high risk group.' She continued: 'It is important to do this because this disease can be very severe and there is a treatment. But it is also an extremely rare disease and any screening test will have a certain number of false positives - which could see parents told their child has this disease when they do not.'