Doctors are now using genetic information in an effort to identify and prevent heart problems in patients who seem healthy but may be at risk because of a family history of heart diseases, says Professor Steve Humphries.
At the ‘challenges and innovations in cardiometabolic disease’ event this month Professor Humphries, BHF Professor of Cardiovascular Genetics at UCL and Director of the BRC-supported UCL Genetics Institute, gave an insight into the issues surrounding genetic testing for risk of heart disease.
Professor Humphries explained how an individual's risk of heart disease is currently based on classical risk factors such as age, gender, blood pressure, smoking habits and obesity. However, most heart attacks occur in individuals with only average classical risk factors. Family history of heart disease is also an important predictor and if doctors can identify specific genes and DNA variants which explain an individual’s specific family history risk it could help influence the lifestyle and drug advice they give to individuals.
To identify these specific genes and DNA variants researchers look for one or more single nucleotide polymorphisms (SNPs), the most common type of genetic variation among people. Each SNP represents a difference in a single DNA building block, called a nucleotide.
Research has shown SNPs can help predict an individual’s response to certain drugs, susceptibility to environmental factors such as toxins, and risk of developing many complex diseases such as cancer, diabetes and heart disease. SNPs can also be used to track the inheritance of disease genes within families.
Professor Humphries highlighted the importance of using genetic testing to obtain ‘personal’ DNA information, rather than employing current health guidelines only.
Current guidelines mean that only people who have a greater than 20% chance of developing heart disease within the next 10 years – as calculated using risk score algorithms – will be prescribed statins. Anyone with a lower than 20% chance of developing heart disease within the next 10 years will simply be encouraged to improve their lifestyle.
Although this may seem reasonable, a study carried out by Professor Humphries and his team in 2006 highlighted a major weakness.
In a study group of 3000 men, a test revealed a hidden group of genetically susceptible men whose actual risk of heart disease was much higher than predicted by traditional assessment methods, which measures risk indicators such as blood pressure, cholesterol and weight.
The men were followed for over 15 years. Over this time, more than 250 developed heart disease, and the majority of heart attacks occurred in men who had been predicted as being at moderate – rather than high – risk.
Professor Humphries concluded his presentation stressing that genetic testing could help people to make positive changes to their lifestyle: if people know that they may be at higher risk, they may be more likely to change their behaviour and adhere to taking medication.
This type of genetic testing for heart disease is ready and can be of use, although widespread use within the NHS is not imminent.
