Every baby born in Ireland has a heel prick test within 120 hours of their birth - the results of which could save their lives. Susan Hayden reports.
Not many people realise that the deceptively simple heel prick test performed on newborn babies can help prevent retardation and even death in some cases. All 60,000 tests taken in Ireland in this critical neo-natal screening process come through the Newborn Screening Laboratory based in Temple Street Hospital.
The unit was established in 1966 in order to screen for Phenylketonuria (PKU) - a condition in which the baby is unable to metabolise an amino acid, phenylalanine, which has a direct toxic effect on the brain in high levels.
It affects one in 12,000 infants worldwide, but its incidence rate in Ireland is much higher, one in 4,500.
"It is likely that PKU started in Ireland and Eastern Europe and spread from there," says Dr Philip Mayne, director of the Newborn Screening Laboratory. "The further away you go, the lower the incidence."
Left untreated, PKU can cause severe retardation, requiring institutionalisation, but a diet that avoids high-protein foods (such as breast milk or formula based on cow's milk) allows the affected child to lead a normal life.
Since then, four other disorders have been added to the screening process. All have three things in common - they can all cause retardation and/or death; they are preventable through diet or medication, if identified in time; and all have a much higher incidence rate in Ireland than the in the rest of the world.
The disorders are:
Maple Syrup Urine disease (affects one in 125,000): occurs when the body can't use some components of food proteins, can cause premature death.
Galactosaemia (affects one in 19,000): occurs when babies can't convert galactose, a milk sugar, into glucose, can cause premature death;
Congenital Hypothyroidism (affects one in 3,500): results from the failure of the thyroid gland to produce thyroxine, causes cretinism;
Homocystinuria (affects one in 65,000): due to a lack of enzymes in the liver, increases the chances of having a heart attack or stroke.
Of the five disorders, four are hereditary. In the case of PKU, "If both parents carry the abnormal gene, their child has a one in four chance of getting the disorder," explains Dr Mayne.
For Galactosaemia, those at high risk include siblings of those affected and the children of those who tend to marry within a very small group, such as the Travelling Community, where the incidence of Galactosaemia is one in 450.
Parents in these casesare advised to give their children a lactose-free food from birth and to arrange an early screening for them. Hypothryroidism is the only disorder that can be treated locally, the others all require regular visits to Temple Street Hospital.
Women who have PKU are advised to plan their families so that their condition is under control at the time of conception, as PKU is actively transported across the placenta.
Although the risks of their child also having the disorder are small (as the father must also carry the abnormal gene), he or she could get some of the complications of PKU without having the disorder itself.
Most people will only come into contact with the heel prick test when they have had a child. The health boards are responsible for screening and the test is either administered in hospital or by a public health nurse if the child has been discharged.
It must be administered between 72 and 120 hours after birth, in order to ensure that the infant has consumed enough protein before the test to avoid a false negative result. The 120-hour limit is to ensure that the child doesn't show the symptoms of the disorder before the test results are available.
The neo-natal screening unit, consisting of just five people, processes over 60,000 tests each year, from 100 locations in Ireland, checking for each of the five disorders.
If the results are clear, the parents of the child will not hear back from the public health nurse. If a condition is diagnosed, the child is referred to the metabolic unit in Temple Street Hospital. There, specialist paediatricians, dieticians, social workers and nurses provide the requisite expertise, care and support.
The metabolic unit also educates the parents about how to manage the disorder, and how to take the requisite twice-weekly tests.
Affected children have to visit Temple Street Hospital frequently, reducing to once every six months during adulthood. If the child gets sick in any way, they have to be monitored even more closely as illness can cause the disorders to spiral out of control.
Showing how close the relationship between the metabolic unit and the child is, the unit's staff send special eggs to each of the children at Easter, as they can't eat normal ones, and they also host Christmas parties for them. The unit has a display of acceptable foods and it also organises occasional cooking demonstrations. A knowledge of food product labelling is critical for affected people. For example, PKU sufferers cannot consume phenylalanine, contained in yoghurts and cola drinks.
As part of an ongoing review of newborn screening, a change from implied consent, as occurs when a parent hands their baby over to a nurse to administer the test, to written consent, is being evaluated.
The final draft recommendation will be submitted to the Chief Medical Officer within the next month.
Currently parents are informed by the maternity hospital about the heel prick test after their baby is born. The test is then administered by the hospital if the baby is still in hospital at the time, or by a public health nurse if the baby has gone home.
Under the new proposals, parents will be asked for written consent before their child is born. This is an attempt to ensure parents are fully informed of the benefits and risks of the heel prick test in advance of having their baby.
Under the Constitution, the rights of the family come before the rights of the individual, allowing parents to refuse the test on behalf of their child. In the event of their child being affected with one of the conditions, and a legal case arising, they are likely to win the case on the basis that a mother who has just given birth is in no state to decide whether or not the test should be administered. With pre-consent, this would no longer be an argument. Such a move would have both positive and negative implications.
On the positive side, Dr Mayne says: "Should parents have doubts about the procedures of newborn screening, obtaining consent during the ante-natal period will provide parents with sufficient time to consider its merits, with the prevention of possible mental handicap."
On the negative side, the workload on public health nurses would increase, as they would need to make two visits to expectant parents instead of one. Although on the face of it, a good idea, a move to written consent prior to the birth of a child could raise other issues. A question arises over the onus of responsibility in the case of an affected child of parents who refuse the test. Should the onus fall on the government and the public health services as is currently the situation, or should it fall on the parents who refused the test that could have helped prevent the condition from arising?