Newborn blood spot screening

Nowadays, CF is usually diagnosed through newborn blood spot screening, which is also known as the heel prick test.

Since 2003 in Scotland and 2007 in the rest of the UK, all babies born have been screened for CF using the heel prick test. As a result most children are diagnosed with CF shortly after birth.

How does the heel prick test work?

The heel prick test is offered when babies are five days old and involves taking a few drops of blood from the baby’s heel. The blood sample is then tested for several serious but rare conditions including cystic fibrosis.

To have cystic fibrosis, an individual must carry two copies of the faulty gene (one copy inherited from their mother, and one from their father). There are lots of different types of faults (mutations) that can affect the gene causing cystic fibrosis. The heel prick test screens for the most common mutations, but not all of them, so it’s possible for someone with a rare genetic mutation not to be picked up by the test and CF may not be diagnosed until later in life.

A positive result from the heel prick test suggests that a baby may have cystic fibrosis, however further tests will be needed to confirm a diagnosis (see next section on the sweat test). This leaflet from Public Health England gives some further detail about receiving a positive heel prick test.

The heel prick test can also identify some babies who have one faulty gene, meaning that they are carriers of the cystic fibrosis gene but are not thought to have the condition. Take a look at Public Health England’s helpful leaflet on this subject.