A new score for predicting the risk of heart disease gives a more accurate measure of how many UK adults are at risk of developing the disease and which adults are most likely to benefit from treatment.
The study published on bmj.com today, estimates that in the general population without pre-existing cardiovascular disease or diabetes, there are 3.2 million adults under the age of 75 in Britain at high risk of developing heart disease. This is lower than previous scores have suggested, but the researchers believe that it is a more appropriate estimate for the UK and will help minimise health inequalities.
The study comes as the government's drugs watchdog, the National Institute for Health and Clinical Excellence, recommends that people with a 20% chance of developing heart disease over the next 10 years should be offered statins.
A person's chance of developing heart disease is estimated using standard risk factors such as age, sex, smoking, blood pressure and cholesterol. This risk score is typically based on equations derived from the US Framingham cohort study.
But the Framingham equations tend to over-predict heart disease risk in the UK population and fail to include measures of deprivation, family history of heart disease, body mass index, and treatment with blood pressure lowering drugs, despite known links between these factors and poor health.
So a team of researchers, from Bristol PCT and the Universities of Nottingham, Bristol and Queen Mary's, set out to derive a new cardiovascular risk score (QRISK) for the UK and test its performance against the established Framingham score and a new a score used in Scotland (ASSIGN), which includes a measure of social deprivation.
The research has been conducted using data from a general practice research database called QRESEARCH (which is a joint partnership between the University of Nottingham and EMIS).
The researchers tracked the progress of 1.28 million healthy men and women, registered at 318 general practices over a period of 12 years to April 2007, recording first diagnosis of cardiovascular disease. All the participants were aged between 35 and 74 at the start of the study.
They found that the QRISK score was more accurate than either Framingham or ASSIGN. In patients aged 35-74, Framingham over-predicted cardiovascular disease risk at 10 years by 35%, ASSIGN by 36% and QRISK by 0.4%. QRISK predicted 9% of patients aged 35-74 years to be at high risk compared with 13% for the Framingham equation and 14% for ASSIGN.
Using this more focused tool for risk estimation, the research team estimate that 34% of women and 73% of men aged 64-75 would be at high risk compared with 24% and 86% according to the Framingham equation.
QRISK would also identify a different group of patients than the Framingham equation, with one in ten patients being reclassified into high or low risk, they say. QRISK is likely to provide more appropriate risk estimates of cardiovascular disease risk based on age, sex and social deprivation, write the authors. It is therefore likely to be a more equitable tool to inform management decisions and help ensure treatments are directed towards those most likely to benefit.
In people under 75 years without pre-existing cardiovascular disease or diabetes QRISK identifies 3.2 million patients at high risk in 2005, compared with 4.7 million from Framingham and 5.1 million from ASSIGN.
They suggest that QRISK should be further tested in other populations, but point out that this is the largest such study to have ever been undertaken, and the first time routine data in a UK general practice population have been used in this way.
Study leader, Professor Julia Hippisley-Cox said "QRISK is derived from primary care data for use in primary care, and takes account of social deprivation to better identify patients most at most risk of heart disease and stroke who are most likely to benefit from treatment.
We thank the many thousands of doctors who have enabled this research by freely contributing anonymised data to QRESEARCH without which this work would not have been possible."