Friday February 19 2016
Around 1 in 100 people has an inherited heart condition
"A new blood test could help diagnose people with inherited heart conditions," BBC News reports.
Inherited heart conditions affect around 1% of the population, and can disrupt the normal functioning of the heart – sometimes with fatal results.
Sometimes a family is only aware they may be at risk of an inherited heart condition when one of the family members dies suddenly, often when exercising.
It is hoped this new test will allow for a more efficient diagnostic protocol for people who are thought to have these conditions. If a condition is present, this should lead to better and earlier management.
There are already methods in use to detect inherited heart conditions, but the researchers wanted to find a method that would cover all genes currently known to be involved in causing such conditions.
They developed a single test that covered 174 genes known or suspected to cause more than 17 different types of inherited heart conditions.
The researchers found their approach had advantages over existing methods, in that it assessed more genes, was quicker, gave more in-depth information than the existing methods it was tested against, and cost less.
The researchers state this test is for research purposes and, ultimately, use in wider clinical practice.
According to the media, the test is already in use at the Royal Brompton and Harefield NHS Foundation Trust, which is where some of the researchers work. If successful, it may be rolled out across the NHS.
Where did the story come from?
The study was carried out by researchers from a number of institutions, including the National Heart Research Institute Singapore and the NIHR Cardiovascular Biomedical Research Unit (BRU) at the Royal Brompton and Harefield NHS Foundation Trust in the UK.
Funding was provided by The National Medical Research Council of Singapore, Goh Foundation, Tanoto Foundation, SingHealth and Duke-NUS Precision Medicine Institute, the UK Medical Research Council, the NIHR Cardiovascular BRU at the Royal Brompton and Harefield NHS Foundation Trust and Imperial College London, the British Heart Foundation, the Wellcome Trust, and the Department of Health.
The authors developed the genetic panel in collaboration with Illumina, the manufacturers of the sequencing technology used in the study. One of the researchers has consulted for Illumina.
The study was published in the peer-reviewed Journal of Cardiovascular Translational Research on an open access basis, so it is free to read online. There is also an editorial that provides a useful overview of the research.
The study has been reported widely in the UK media, but the news stories, while broadly accurate, do not give many details about the study itself.
What kind of research was this?
This laboratory study aimed to develop a diagnostic test suitable for testing for a wide range of inherited heart conditions.
Genetic testing for inherited heart conditions is reported to have started around 20 years ago. Since then, the technology used in genetic testing has advanced, becoming quicker and cheaper, and is used much more widely.
In the past, such tests would have looked at a single gene at a time to identify a single disorder. Today, large tests covering multiple genes and disorders are now frequently used for conditions that are clinically and genetically similar, such as inherited heart conditions.
Inherited heart conditions affect around 1% of the population, and include conditions that cause an abnormal heartbeat or affect the health of the heart muscle, such as cardiomyopathy.
Gene sequencing – scanning a sample of DNA to uncover the genetic information contained in it – for inherited heart conditions can confirm the presence of a particular condition, and allows for better and earlier management.
There are existing methods for detecting these conditions that cover some, but not all, genes known to cause inherited heart conditions.
What did the research involve?
The researchers recruited 348 people from Singapore and London. They took samples of their blood and extracted DNA for use in their tests. The researchers also used eight DNA samples from the National Heart Centre Singapore.
They developed a test that could look at the sequence of 174 genes known or suspected to cause inherited heart conditions.
This included conditions that cause:
- abnormal heart rhythms (arrhythmia)
- abnormalities in the heart muscle (cardiomyopathy)
- abnormalities in the aorta – the main artery in the body, which takes oxygenated blood out of the heart to the rest of the body
- abnormal levels of fats (lipids) in the blood
They then compared their test with a number of other sequencing methods to see how they performed in identifying inherited heart conditions.
The other methods used were broader, not just looking at inherited heart condition genes, but do not look as closely at the sequence of these inherited heart condition genes.
The researchers also looked at whether their test correctly identified genetic variations in these genes in a known DNA sequence.
What were the basic results?
The researchers found their test had a high level of accuracy when tested against known genetic sequences. It was also:
- able to provide better (more complete) coverage of the sequence of the inherited heart condition genes than the broader tests
- quicker than some of the other methods, taking four days to complete instead of nine
- cheaper than some of the other methods – it cost US$200 per sample, as opposed to US$900-5,400 for other methods
How did the researchers interpret the results?
The researchers concluded that their test "delivers highly accurate and affordable sequencing of [inherited cardiac condition] genes".
This study aimed to develop a more comprehensive diagnostic test for a wide range of inherited heart conditions.
The researchers developed a single test that was able to look at 174 genes known or suspected to cause these conditions. It was quicker and gave better coverage of the genes it looked at than the existing methods it was tested against.
Such a test is likely to be very useful when a person is thought to have an inherited heart condition, but it is not known exactly which gene is causing it.
It could help doctors to quickly identify the exact cause and start the person on appropriate treatment, and also learn which gene to look at when they assess other family members for the condition.
The study covers a broad list of genes known or suspected to cause inherited heart conditions. However, we are still discovering things about the genetics of disease, and as this happens other genes might need to be added to the test.
The researchers also noted that their test does not identify all genetic mutations that cause inherited heart conditions.
Despite these limitations, the test seems to give good coverage of the currently known genes. According to the media, this has already been put into practice at the Royal Brompton and Harefield NHS Foundation Trust, where some of the study researchers work.
Whether the test is actually being routinely used in people suspected of having such a condition, or just as part of the ongoing research to further develop the test, was not clear.
It is still early days, and we don't yet know whether this test is ready for wider use.