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Genetic Testing for and Inheritance of Cystic Fibrosis

Genetic Testing for and Inheritance of Cystic Fibrosis

Although technically a rare disease, CF is ranked as one of the most widespread life-shortening genetic diseases and is particularly common among Western nations. It currently affects more than 10,800 people in the UK, and each week in the UK, five babies are born with CF. It's estimated that 1 in every 2,500 babies born in the UK has CF. As CF is an autosomal recessive condition, both parents need to be carriers of CF for a child to be born with CF. Each pregnancy conceived by carrier parents has a 25% chance (1 in 4) of being affected by CF. One in 25 of the general population carries the gene that causes it, usually without any symptoms or knowledge of it. The carrier frequency in the population varies by ethnic group, with the highest number of carriers among people of Northern European ancestry.

What population genetic screening is available for Cystic Fibrosis

Where there is a known chance a pregnancy could be affected by CF (usually because there has been a previous diagnosis of CF in the family), a diagnostic test of the foetus (a CVS test carried out at around nine weeks after conception or amniocentesis at about 15 weeks) is offered on the NHS.

While antenatal genetic screening for CF is not currently available, newborn screening for the condition became available across all of the UK in October 2007. This screening also identifies carriers of the gene. Newborn screening means that babies with CF can be treated as soon as possible with a high-energy diet, medicines, physiotherapy and appropriate care from healthcare workers and parents. This helps them to live longer and healthier lives, with improved growth, healthier lungs, reduced hospital stays and delayed or prevented serious, life-long health problems related to CF.

Currently, within NHS care, only those deemed to be ‘at risk’ of being a carrier are being tested to see if they are carriers of CF. These are usually people who are the blood relatives of a person with CF, or the partner of someone with CF, with whom they want to have children. However, private genetics companies are increasingly offering carrier and prenatal screening to anyone who is willing and able to pay for the test.

Importantly for families living with CF, the genetic testing technologies which are used to diagnose CF, and also to identify carriers of CF, cannot accurately predict which symptoms and the severity that a child will inherit . This issue makes the question of screening for CF far more complex than for some other conditions.