Inconclusive diagnosis after a positive screening for cystic fibrosis

Does my baby have cystic fibrosis?

Your baby does not have a diagnosis of cystic fibrosis (CF). The screening result from the heel prick was positive but the follow-up sweat test does not confirm a diagnosis of cystic fibrosis.

Visit the NHS page on the newborn blood spot test for more information.

Does my baby have CFSPID?

Your baby has been described as having ‘cystic fibrosis screen positive, inconclusive diagnosis’, which is often shortened to CFSPID. This is not a condition, a disease, or a syndrome. It is a name to describe having a positive screening result, but not a clear diagnosis of cystic fiborsis.

Is my baby healthy?

Yes your baby is healthy. Your baby has been assessed by the cystic fibrosis team and is healthy. CFSPID means there are some things you should be aware of to make sure your child stays well.

Is my baby at risk of developing CF?

There is a small chance that your baby may develop a form of CF as they grow older.

How will I know?

There are 2 main ways a child with CFSPID could convert to a diagnosis of cystic fibrosis as they grow older.

The first is if a child with CFSPID develops symptoms that seem like cystic fibrosis.

The most common symptom of cystic fibrosis is a cough, and if your baby has a cough that persists for more than 2 weeks you should contact your GP or the cystic fibrosis team. Your cystic fibrosis team will continue to monitor and discuss your child’s growth with you.

The other way of knowing is by having a repeat sweat test that shows there is more salt in the sweat. Sweat tests will be repeated during childhood at intervals agreed with the cystic fibrosis team.

A reminder about screening

You may remember being offered newborn screening for your baby when they were around 5 days old. A small blood sample (‘heel prick’) was collected by the midwife on a card. The blood was tested for some rare inherited genetic conditions, including cystic fibrosis.

A positive screening result suggests that a baby may have one of these conditions. Specialist teams will then arrange follow-up tests to confirm a diagnosis. In most cases, this leads to a definite diagnosis which allows affected babies to start treatment quickly. In some cases, the screening result is positive but the follow-up tests are inconclusive.

What is the chance that a baby with a positive screening result has CFSPID?

For every 300 babies in the UK that have a positive screening for cystic fibrosis:

• 225 are diagnosed with cystic fibrosis
• 60 do not have cystic fibrosis
• 15 have CFSPID

What is cystic fibrosis (CF)?

Cystic fibrosis is a lifelong inherited condition. Although the outlook for people with cystic fibrosis has improved, especially with new therapies, it is still a condition that affects children and their families.

Babies with cystic fibrosis look and develop the same as other babies, but having cystic fibrosis means that they may struggle to gain weight and are prone to chest infections. Screening for cystic fibrosis usually means that doctors can diagnose cystic fibrosis with further tests, such as the sweat test, and start treatment quickly.

What is a sweat test?

A sweat test is the main way we can check for cystic fibrosis after a positive newborn screening result. To do this test we collect sweat from the skin and then measure the amount of salt in the sweat.

People with cystic fibrosis have a lot of salt in their sweat because of how the genes affect the cells. We can tell from the amount of salt in the sweat if someone has cystic fibrosis.

Are some children with CFSPID more at risk than others?

Some children with CFSPID have a slightly higher amount of salt in their sweat. Children with CFSPID who have a higher amount of salt have a higher chance of developing cystic fibrosis than children with a lower amount of salt in their sweat.

What does the sweat test number mean?

The amount of salt in the sweat is given a number. A measure over 60 is high and consistent with a diagnosis of cystic fibrosis. A measure under 30 is considered normal. A measure between 30 and 60 is called intermediate. Children with a number nearer to 60 have a higher chance of developing cystic fibrosis. The cystic fibrosis team may want to see these children more often and do repeat sweat tests. Please discuss this with your cystic fibrosis team.

Visit the Cystic Fibrosis Trust about the sweat test for more information.

How often will we need to see the cystic fibrosis team?

This is different for each family. The cystic fibrosis team will outline the plan and the pathway of care for your child and advise as to what information we will collect such as height, weight, sweat test and a poo sample.

With your permission this information will be included on a national registry, which aims to better understand the outlook for children with CFSPID.

Guidance suggests that your team will see your child at least once a year until they start school. At that point you might discuss future arrangements with your cystic fibrosis team or doctor.

Is there anything else we should be aware of?

The gene that is affected in cystic fibrosis is called the cystic fibrosis transmembrane conductance regulator (CFTR) gene.

Children with CFSPID may have some changes to the CFTR gene that may be important later in life. These changes may cause conditions called CFTR-related disorders. These conditions are not cystic fibrosis, but they are important to be aware of. The chance of having these conditions in the general population is very low. The chance is increased for young people with CFSPID, although we do not yet know by how much.

What do these ‘CFTR-related disorders’ mean for young people?

The most clearly identified CFTR-related disorders are congenital bilateral absence of vas deferens (CBAVD) and pancreatitis. Pancreatitis is associated with episodes of severe tummy pain. There is a straightforward test for pancreatitis. It is important to tell a doctor about your child’s CFSPID if they have severe tummy pain.

CBAVD is a cause of infertility for men, which is easy to diagnose. Men with CBAVD produce normal sperm and are able to have children through assisted fertilisation (commonly known as IVF). This will be discussed during teenage years with the you, your child, and your GP.

What about if we decide to have more children?

We are happy to discuss future fertility options and testing with you, and can put you in touch with genetic counsellors for more detailed advice. You may have questions about the chance of having another child with CFSPID and we can explain this to you face to face.

Is this result important to other members of our family?

Because CFSPID involves genes, this may be relevant to other people in your family. For example, aunts and uncles who are considering having children. Your family members can make an appointment to review this with a genetic counsellor. This can be organised through their GP.

When should I talk to my child about this?

As your child gets older, it is important that they know about this information so they can take steps to stay well.  There is no ‘right time’ – it depends on your child and your family. The cystic fibrosis team can help discuss CFSPID sensitively and answer any questions with you and your child as they grow up.

Why has this happened? Is it our fault our baby has CFSPID?

It is no one’s fault that your baby has CFSPID, but this is a surprisingly common feeling for parents in this situation.

Your baby has inherited the cystic fibrosis gene changes from you in the same way they may have inherited your eye colour and hair colour. We have no control over the genes that we pass on to our children so this could not have been prevented. Everyone copes in their own way when their baby is diagnosed with CFSPID, and help and support is available when you need it.

Summary

In summary, it is important to remember that your baby is well, and even if they convert to a diagnosis of cystic fibrosis or develop a CFTR-related disorder in later life, this information will help them to stay well.