What’s hidden in the blood

Every parent-to-be knows the apprehension that goes with all the unknowns accompanying a new child.

One of the greatest and oftenunspoken fears is that somewhere in the child’s DNA will lurk a disorder just waiting to spring a shocking surprise.

Modern newborn screening allows doctors to test for some 50 genetic disorders, thereby helping parents avoid at least some of the unknowns.

For those whose children test negative, it is a great relief.

However, those whose children test positive for a disorder start down another path where even though the fear is not gone, at least they know and can start doing something about it.

Starting small

The modern newborn screening programme is a far cry from the origins of the genetic screening programme in the Cayman Islands.

The programme started in 1978, initially to research Cayman Ataxia, formerly known as Cayman Disease.

“Dr. Arthur Bloom, a geneticist from Columbia University in New York had been down here and seen one or two genetic type patients on the streets and together with Nurse Josie Solomon, who was the head nurse in public health at that time, they went out into the districts and sought out some of these patients, and it all evolved from there,” said Dr. Marilyn McIntyre, head of paediatrics at the Cayman Islands Hospital.

At first it was only possible to detect a limited number of disorders with newborn screening, PKU and congenital thyroidism were the first disorders to be tested for. This was supplemented by a test for sickle cell disorder in 1997.

The full, newborn screening programme was instituted in 2002.

The test could initially identify some 35 disorders, but this has increased to more than 50 disorders detectable under the current testing protocol.

No stigma

One of the issues often encountered with genetic screening programmes like the one in Cayman is that parents feel guilty for any disorders their children may inherit.

“All of us have abnormal genes. They say we’re all carriers for between three and six disorders, but most of us go through life and we don’t know that. Of course, as we’re testing more now, we find out some of those things,” said Joy Merren, genetics coordinator at the Cayman Islands Hospital.

According to McIntyre, people need to realise that these abnormal genes are not related to your lifestyle or any conscious choice you make.

“We all carry different genes, whether it be blue eyes, brown eyes, and there’s no slur on anybody for what they have. It’s nothing that anybody has done wrong, it’s just a fact of life,” said McIntyre.

Agenetics primer

One of the greatest challenges faced by the medical staff involved in the genetics programme is explaining the basics of genetics to parents-to-be.

“Basically we all have two genes for everything, whether it be the blue eyes, the brown eyes, everything – one from the mother and one from the father,” said McIntyre.

“If you’re a carrier, one of your genes has the condition, and the other gene is so-called normal. So if both parents are carriers, you have a one in four chance of having an affected baby.”

However, this does not mean that every fourth child is going to have the disorder, and it most certainly does not mean that if the first child had the disorder, the next three will be fine.

“Every pregnancy has a one in four chance because you can get the affected gene from your mother and the affected gene from your father, and that is going to give you a fully affected child, a child with the disease.

You have a one in four chance in every pregnancy of having a normal child, because if the child inherits the so-called normal gene from the mother and the normal gene from the father, it’s not even going to be a carrier.

But then you have a one in two chance of being a carrier, because you can have a so-called abnormal gene from your mother and a normal from your father, or the abnormal from your father and the normal from your father,” said McIntyre.

What the test involves

The newborn screening test is a quick and relatively painless affair, which involves the collection of a small amount of blood from the baby.

“The way the test is done is to get the blood from a heel prick sample, that’s collected onto a filter paper. We fill out the information on the paper and then the filter paper side is attached so there are five circles and we fill those circles with blood.

They’re then dried, just air dried in the room. We send them off to the lab that we’re affiliated with,” said Shannon Hydes, nurse manager for the maternity unit at the Cayman Islands Hospital.

Due to the nature of genetic disorders, it is important that statistics on the disorders be as complete as possible, which is why the cooperation of parents is very important to the programme.

Parents who attend the parent craft classes at the Cayman Islands Hospital receive information about the newborn screening programme. However, as many parents do not attend these classes, the information is also provided in the hospital.

“Once the baby is born, we give [the parents] this same information and we ask them to read it over and let us know if they want their baby to have it. We don’t force them, but we try to impress on them that it is very important to have it done.

It is usually covered by insurance and those that are not covered by insurance, public health picks up the cost,” said Hydes.

According to Hydes, once parents have been provided with the information on the test, most of them agree to have their child tested.

“We have had one or two that have said no, then we have to guide them to their paediatrician and get them a little bit more in-depth explanation of everything and then usually they see the wisdom of it and they get it done. I’m pretty safe in saying all the babies get screened,” said Hydes.

Screenings are also conducted on Cayman Brac and at Chrissie Tomlinson Memorial Hospital, so any child born in the Cayman Islands should be covered.

According to Hydes, the only cases in which a child might not be tested is if the child has to be evacuated by air ambulance immediately. However, in most of those cases, the child is tested elsewhere.

Although the test can be conducted immediately, if it takes place before the first 24 hours have elapsed, it is advisable that it be taken again. It is also important that the child has beenfed before the test is administered.

Although the test can be administered later on, the cystic fibrosis portion of the test is not valid if the test is conducted more than three months after birth.

What they find

The two most prevalent disorders found during the newborn screening process are sickle cell disease and glucose 6 phosphate dehydrogenase deficiency.

With sickle cell disease, the known number of sufferers in Cayman is 41, but many people are identified as carriers of sickle cell genes.

“In the Caribbean, one in 10 generally has sickle cell traits. Here, since we started in 1997, such as the statistics that I have, our percentage of the sickle births, and I include in that the few that actually have the disease, because it is not a lot, are 5.3 per cent, as compared to the 10 per cent,” said Merren.

“What happens in sickle cell is that the red cells instead of being circular become sickle shaped, and because they are sickle shaped they clump together, and if they clump together then they can form clots in the blood vessels, which can then prevent the blood getting to various essential organs, particularly the brain, in which case you can end up almost like a stroke,” said McIntyre.

However, with early diagnosis those with the disorder can be closely monitored and preventive steps can be taken to avoid complications.

The other most common disorder diagnosed is glucose 6 phosphate dehydrogenase deficiency, or G6PD for short.

This is a disorder that affects the stability of red blood cells and causes them to die off more quickly than in people without the deficiency.

However, under most circumstances, the disorder might never become apparent.

Exposure to certain chemicals or even food can cause a haemolytic episode, during which red blood cells can die off in large numbers, too quickly for the body to replace effectively.

In these cases a blood transfusion could be needed in order to ensure the health of the patient.

It is the most prevalent genetic disorder globally, with some 400 million people suffering from it.

The disorder usually only manifests in males, even though females can often be carriers, but in rare cases females can have the disorder when the father suffers from the disorder and the mother is a carrier.

“Since 2002 we have had 216 positives that actually have the disorder, and before that we had eight that were known. Out of those, we have 18 girls,” said Merren.

With early diagnosis and counselling, the potential impact of both disorders can be managed, which is why all cases identified as positive for a genetic disorder are referred to Merren for counselling.

Follow up

Once a diagnosis has been made, the parents are referred to Merren for counselling.

This includes information on how to deal with the disorder, as well as counselling on the likelihood that future pregnancies might be affected in the same way.

“The sooner you can find out if a child has a certain disorder, then you can treat and it can make a difference. With most of the disorders, we don’t have a cure, but we can manage it, and for instance with G6PD if we know a child has that we can tell parents what to prevent the child from being around that can make a big difference in the child’s life,” said Merren.

Since testing for the disorder started in 2002, Merren does not know of any cases of complications related to G6PD, although she does recall a couple of cases prior to the newborn screening programme.

With the number of cases of the disease in Cayman, the mere fact that there have not been any recorded complications indicates the value of a newborn screening programme.

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