The impact of a major gene study that identified hundreds of rare diseases in those taking part could ‘revolutionise medical care’.

Scientists examined participants’ entire genome – their complete set of genetic information – and one in four received a new diagnosis.

Now the team behind the study have said it could lead more focussed treatments and improved care.

Almost 2,000 families took part after being recruited through the 100,000 Genomes Project.

It provided a breakthrough for one 10-year-old girl with an unknown condition who had previously visited hospital more than 300 times and been admitted to intensive care on several occasions. Thanks to the study, she received a diagnosis which led to her having a bone marrow transplant, while testing also revealed none of her family members were at risk.

It is the first time that whole genome sequencing has been applied to large numbers of people with rare diseases and used in a healthcare system.

The study, led by Genomics England and Queen Mary University of London, has been described as a “major advance” by Professor Sir Mark Caulfield from the university and former chief scientist at Genomics England. He also said it could get the ball rolling for the technique to be used in the NHS.

Among those who benefited from the study was Terri Hedley and her family. Terri inherited a kidney condition from her dad, Leslie, who has been treated for years for a serious kidney disease.

However, the genome sequencing technique revealed that Terri’s daughter Katie did not have the kidney problem.

Terri said: “It was fantastic to know that it stops with me. She doesn’t need to get regular tests now. We were so worried about her.”

For many of those who took part in the study, it provided answers about their rare condition after years of testing and appointments. It led to improvements in care, including a change of diet and other therapies.

Of those diagnosed, 14 per cent were found in area of the genome which meant it would have gone undetected with traditional testing.

The main rare diseases to be identified were eye conditions, neurodevelopmental conditions, and metabolic conditions related to diabetes, high blood pressure and obesity.

Genome sequencing is the process of examining entire genomes, which are three billion letters long and found in almost every cell.

Scientists aim to identify the differences between one person’s genome and a ‘reference’ genome and by using specialist software, they can see which differences could be causing the disease.

Prof Damian Smedley, from the Queen Mary research team, said the new technique “was key to us being able to solve the ‘needle in a haystack’ challenge of finding the cause of a rare disease patient’s condition amongst the millions of variants in every genome”.

Prof Chris Inglehearn, professor of molecular ophthalmology at the University of Leeds, said the results proved “beyond doubt” that genome sequencing “can revolutionise medical care for a wide range of human diseases”.

The challenge, he said, was that the data “can prove difficult for clinicians and researchers to access” – an issue that should be addressed.

How whole genome sequencing could be used within the NHS to identify rare diseases is another challenge, scientists said.

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