The heel prick test has changed many lives since it was introduced in the Republic in 1966 for all newborn babies
LIKE MOST parents, Karen Wood knew the heel prick test was routine for newborn babies, but she did not know exactly what it was for. When her second daughter, Zoe, had it done two days after her birth in the Rotunda Hospital, Karen was more concerned about being discharged so she could be home for her first daughter’s birthday that day.
Once a baby is tested, it is usually the last the parents hear of it. But not for Karen and her husband Eddie.
The next day, the Rotunda rang their home in Balbriggan, Co Dublin, asking them to bring Zoe back for a re-test. When Karen said they would get in later that week, she was told it could not wait.
“When they are insisting you come back in that day . . . I started to panic and be upset,” she recalls. Within 24 hours, they were referred to Temple Street children’s hospital and advised that they might be there for a few days.
“I still hadn’t a flipping clue what was going on,” says Karen. “I just knew something was up and they had to re-test the blood.”
At Temple Street’s metabolic unit, everything was explained. Zoe had tested positive for a condition the Woods had never heard of: phenylketonuria, or PKU for short. It is a rare genetic disorder, but Ireland has one of the highest incidence rates in the world – at about one per 4,500 births. PKU occurs only when both parents are carriers, and then there is a one in four chance that any baby of theirs will have it.
Zoe’s body lacks the enzyme necessary to break down a particular amino acid, one of the approximate 20 “building blocks” which make up protein. Left untreated, the condition would cause that amino acid to accumulate as a toxin and interfere with brain development.
It was a relief for Karen to hear that Zoe would be fine as long as she was immediately put on a protein-restricted diet, which she would have to follow for the rest of her life. But, disturbingly, they very quickly figured out that Zoe’s condition must be linked to problems experienced by siblings of Eddie.
He has a sister in care and a brother in sheltered housing, explains Karen. They were born before 1966, the year the heel prick test was introduced in the Republic to screen every newborn baby for PKU and other metabolic disorders.
“Knowing what could have been and knowing what had been avoided was one thing anyway,” says Karen, although it was at the back of her mind that Zoe could still end up like Eddie’s siblings “if we didn’t get things right”.
The metabolic unit in Temple Street helps 600-plus PKU patients throughout the Republic, adults as well as children, to “get it right”. A multi-disciplinary team of nurses, doctors, dieticians, psychologists and social workers is available and every year, another 12-16 babies are referred there.
The diet sounds daunting to parents of newly diagnosed babies. Initially, when you are told no dairy, no eggs, no meat, no fish, you are wondering what on earth the child is going to eat, says Karen. They can’t have ordinary rice, pasta, bread, cakes or biscuits either – but low-protein versions of these and other foods are supplied on prescription. While they can eat fruit and some vegetables freely, that would not include beans or nuts.
It is a delicate juggling act to make sure the children have a balanced diet, eating enough protein to develop normally but staying clear of food that could damage them. So they take a formula drink three times a day, which contains protein without the one amino acid, called phenylalanine (phe), that they can’t break down.
However, it is not simply a question of avoiding phe altogether, because they need a little for growth. So they must eat some normal protein – exactly how much is determined by regular blood tests to check there is some phe in their bodies, but not too much.
Newborn babies with PKU are admitted to Temple Street hospital for up to a week, so that their high levels of phe, resulting from having usual amounts of breast or formula milk, can be monitored and reduced. It is also a time to teach parents not only what the complex diet involves but also how to take blood samples from their babies to send in for testing, explains the manager of the hospital’s metabolic unit, Anne Clark.
“You can have a completely normal life as long as you stick to the diet,” she stresses. However, “because the diet is difficult there can be issues around compliance”.
Most PKU patients require 4g-6g of protein a day, says Clark. “To put that into perspective, a slice of ordinary bread has 3g of protein in it.” They measure their consumption of normal protein in “exchanges” and, on average, they would need four a day.
Feeding Zoe, who is now two- and-a-half, is quite a struggle. “She is a normal two year old, but she doesn’t eat,” says Karen. “I have often questioned is that down to her condition, our concern about her condition or would she be that way regardless? Always in the back of my head is, are we putting her off her food because we are watching everything she eats?”
To complicate matters, Zoe had a reflux condition and would bring up a bottle or two a day as a baby. She still tends to vomit about once a week, so they are never quite sure what food she has had.
“At the beginning I would have been more anxious and more stressed about the whole thing than I am now,” says Karen. “I am concerned about what she eats, but if she does eat a bit of chocolate, I am not freaked out. That’s just an exchange in your head. You do learn to get on with it and there are worse things you could come up against.”
They found doing the blood tests very difficult in the first few months as they had to take blood from Zoe’s heel every week and get it into a vial. But before she was one, they could move on to putting the blood sample onto a card which is much easier.
They now take blood from Zoe’s big toe once a week and that will continue until she’s four. “She gets involved,” says Karen. “We give her her own pin and she is play acting along with it. Initially, she doesn’t want to do it, but it gets done and then it is all over in five minutes.” The blood is posted to the clinic where the levels of phe are checked and the number of daily exchanges allowed for Zoe may be increased or decreased as a result.
There is a PKU association, which brings parents of affected children together, and Karen has found it “brilliant” to be able to talk to other mothers who are dealing with the same issues.
“Nice as the dieticians are, they still don’t understand the problems I am having with her eating,” she comments. Potato is one thing Zoe likes, but she is only allowed a small one, or six chips. However, one advantage of Zoe being a picky eater is that she is not demanding to try what everybody else has.
“She likes our bread, which we are not supposed to give her,” admits Karen. “Now she has it down to a fine art and says, ‘Just a little bit’, and we’ll give her the corner or a bit of crust.”
At present, Zoe is cared for at home by her grandmother or Eddie, while Karen works four days a week as the manager of a transport company, but next year they will be putting her into a playschool or creche.
“Then you’re into another whole world of things because you have to be telling people, you have to get them to monitor her intake and that’s the age where she’ll be mingling more with kids. You’re going to get into issues of ‘I want what she has’ – I think we have all that ahead of us yet,” says Karen.
The clinic works directly with the children, helping them to understand why they need to stick to their diet when their peers are dining out on hamburgers and pizzas. “At certain ages they do decide they’ve had enough,” says Clark. “It would be unfair to say that it is just teenagers; it varies and depends on what else is going on.”
In Ireland, PKU patients have always been advised to stay on the diet for life, she adds. “In certain other countries they only do it to a certain age, but we have seen deterioration in their moods, ability to concentrate and reductions in IQ, so we would not have recommended that.”
Getting the vital formula drink into children three times a day can be difficult, but Karen is glad to say that with Zoe it is not a problem. However, she will only drink it out of a bottle, while she’ll drink everything else from an open cup, and Karen thinks it is time to get rid of the bottles.
“She has agreed that Santa will be getting the bottles. But I can’t actually see that happening and I can’t insist because she has to have it.”
They can give the bottles to Santa, she adds, but if Zoe stops drinking her formula, he will have to bring them back.
- swayman@irishtimes.com
'I felt very guilty thaty I had been caught immediately and she hadn't'
The contrasting lives of Cliana Smyth and her older sister Iseult are a poignant reminder of scientific advances within one generation.
Both have the genetic disorder PKU, but Iseult was born before screening for the condition was introduced in the Republic in 1966 for all newborn babies, through the heel prick test. She is intellectually disabled and lives in the care of Stewart’s Hospital in Palmerstown, Dublin.
In the case of Cliana (34), a university-educated PA/administrator, the condition was identified straight after her birth in 1975. By that stage it was known that simply putting her on a low-protein diet would ensure her healthy development and she now leads a completely normal life, apart from what she eats.
“I felt very guilty growing up that I had been caught immediately and she hadn’t,” says Cliana, who also has two brothers, one of whom has PKU and the other hasn’t. “It was nobody’s fault, but it was almost like survivor’s guilt.”
Glowing with good health, Cliana is expecting her first baby next March. But pregnancy is a tricky time for women with PKU and she is being closely monitored by the metabolic unit at Temple Street hospital. She speaks to staff there at least twice a week, and every Monday and Thursday mornings posts them a sample of her blood to make sure she is eating the right amount of protein for her and her baby.
In the first weeks of pregnancy, excess phenylalanine in Cliana’s system could have crossed the placenta and affected the baby’s brain development. So at that stage she could eat hardly any normal protein.
As the pregnancy progresses, the baby can deal with a certain level of phenylalanine. So now, 25 weeks into her pregnancy, Cliana is up to 21 “exchanges” a day, compared with her normal eight. That is quite a challenge for somebody who has always been on a low-protein diet. For the first time in her life, she could actually eat meat. “But I really do not want to go down that path,” she explains. “I am slightly afraid I might like it and then have to give it up.”
She has temporarily stopped using the low-protein versions of food supplied to PKU patients as she has to make sure she consumes enough protein. Plenty of yogurt and potatoes are on her menu.
Although it is undoubtedly an anxious time for Cliana, she knows she is receiving good care, not only from Temple Street hospital but also Holles Street maternity hospital, where she is getting extra scans to ensure the baby is developing normally.
“Because our diet is so carefully controlled during pregnancy, and we get all the vitamins and all the minerals, and everything is checked all the time, we actually end up less at risk from having children born with other things, which is quite reassuring,”adds Cliana.
