As we get older we all have some risk of developing ‘hardening of the arteries’ (atheroma) which can lead to cardiovascular disease – a heart attack or stroke for example. Factors that increase the risk are used in cardiac risk assessment which calculates the probability of cardiovascular disease developing within a defined period. This can then provide guidance on your personal risk and the steps that should be taken to reduce your risk.
Cardiac Risk Assessment
NHS GP practices invite patients aged between 40 and 75 who are not already being treated for heart disease, diabetes or kidney disease to attend for cardiac risk assessment. The assessment is repeated every five years. If you are also known to have higher cardiac risk e.g. familial hypercholesterolaemia, then other risk factors may be screened for but risk calculation will not be done as you will already be eligible for treatment to reduce risk.
First, you are asked to answer questions about the three kinds of risk factor. If you have a strong family history (your mother, father, sister or brother having had a heart attack or angina before 60) it is likely that your immediate family of all ages will also be invited to attend for risk assessment.
Your blood pressure is taken and your height and weight are measured. Height and weight are used to calculate your body mass index (BMI) as a measure of obesity.
No preparation is required. Traditionally fasting samples were used for lipids and glucose. Nowadays HbA1c has largely replaced glucose and is not affected by fasting status. Lipids may be abnormal just after a meal but this indicates worse cardiovascular risk therefore non-fasting specimens are not only acceptable but also preferred.
The risk factors for heart attack and stroke can be divided into those that can be reduced by altering life-style, those that are potentially treatable and those that are fixed. Life-style risk factors are smoking, lack of exercise, obesity, an unhealthy diet and excess alcohol. Fixed risk factors include having a strong family history, belonging to certain ethnic groups (for example, being of South Asian ancestry), your age, and being male or being female after an early menopause. Age and social deprivation are risk factors that are, of course, not permanently fixed.
Potentially treatable risk factors include high blood pressure (hypertension), an abnormal plasma lipid profile (cholesterol and triglycerides), diabetes mellitus and kidney disease. A blood sample is therefore sent to a laboratory for measurement of a lipid profile, the most important blood test for risk assessment. It measures cholesterol, high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C) and triglycerides. Below are the desirable ranges for the components of the lipid profile:
- Total cholesterol 5.0 mmol/L or less
- HDL-cholesterol 1.20 mmol/L or more
- LDL-cholesterol 3.0 mmol/L or less
- Triglycerides 1.70 mmol/L or less
The blood sample may be analysed for two other potentially treatable risk factors. Plasma glycated haemoglobin (HbA1c) may be measured for the diagnosis of diabetes mellitus. Plasma creatinine may also be measured. Together with your age, weight and gender, it is used to calculate your estimated glomerular filtration rate (eGFR) for the diagnosis of kidney disease.
Other blood tests that have been proposed for cardiac risk prediction include high sensitivity C-reactive protein (hsCRP) and lipoprotein A (Lp(a)). However, there is no clear consensus about their use and they are not routine tests.
How is it used?
Firstly to estimate an individual’s cardiovascular risk. There has been a large amount of research into the best way of calculating cardiovascular risk from assessed risk factors. The National Institute for Health and Care Excellence (NICE) recommends the computer program QRISK® as the preferred method, and this is now integrated into all four of the main UK general practice computer systems. Computer input includes age, sex, ethnicity, postcode (to assess social deprivation), smoking status, and selected medical and family history together with systolic blood pressure, body mass index (BMI) and the total cholesterol/HDL-cholesterol ratio.
QRISK® calculates a risk score for the chance of developing cardiovascular disease over the next ten years. A risk score of 10%, for example, means that there is a one in ten chance. Because risk increases with age, and is higher in men than women and also in certain ethnic groups, the program also produces a relative risk score: the ratio of the calculated risk to the risk in healthy people of the same age, sex and ethnicity. For example, an older man might have a risk score of 20% but a relative risk score of 1.0 because he has the risk to be expected in a healthy man of his age. For more about QRISK® click its ‘Information’ tab.
Most people, but not all, can reduce whatever risk they have of developing a cardiovascular disease by changes to their lifestyle. They should stop smoking, avoid passive smoking, increase physical activity, lose weight if overweight, eat a healthy diet and limit alcohol consumption. Repeat assessment will show how well they have succeeded in reducing their risk.
In 2014 NICE recommended that for people with a Q®RISK risk score of 10% or more, GPs should not only offer life-style advice and help but also discuss the benefits and risks of taking a cholesterol-lowering drug. This will, in combination with life-style changes reduce their risk but of course is an individual decision based on the person’s preferences and priorities.
When is it requested?
What does the test result mean?
QRISK® calculates a risk score for the chance of developing cardiovascular disease over the next ten years. A risk score of 10%, for example, means that there is a one in ten chance. Because risk increases with age, and is higher in men than women and also in certain ethnic groups, the program also produces a relative risk score: the ratio of the calculated risk to the risk in healthy people of the same age, sex and ethnicity. For example, an elderly man might have a risk score of 20% but a relative risk score of 1.0 because he has the risk to be expected in a healthy man of his age. For more about QRISK® click its ‘Information’ tab.
The 10% means that of ten identical people to you 1 of you would have an event e.g. heart attack, in the next 10 years (which is the threshold for offering treatments). We do know that the calculator is only an estimate and can underestimate risk, particularly in the young, and overestimates it in the elderly.
Is there anything else I should know?
Cardiac risk calculators are always being improved as we learn more. They are a tool to be used with the person’s preferences and taking into account other medical conditions to help the decision making around how aggressively risk factors for cardiovascular disease need to be managed. Irrespective of current risk healthy lifestyle will always improve risk in the long term. Also as age is the main driver of risk in these calculators as you get older the risk will always get higher. However if you have lost weight, stopped smoking, reduced your blood pressure and cholesterol in reality you will have reduced your risk and this effect will be underestimated by the calculators. This is also relevant for decisions in later life for example stopping statin medications. We know that good risk factor modification provides long lasting protection so deciding to stop interventions later in life, or due to severe concurrent illnesses, will have a minor effect in comparison to life-long good risk factor modification. It can take decades to accrue cardiovascular disease which is why despite worsening risk as per the calculator starting lipid lowering medication is not a decision to take the life long.