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 MeReC Bulletin

Assessing and communicating the risk of cardiovascular disease
Volume 19 Number 1
July 2008

   

Why is CVD risk assessment important?
Who benefits most from CVD risk reduction?
What is meant by high risk?
Single or multiple risk factors for assessing CVD risk?
Which CVD risk assessment tool should be used?
 How do I identify people for formal risk assessment?
How do I carry out a formal risk assessment?
Should I use a risk calculator for people with type 2 diabetes?
How do I communicate risk to patients?



 

Summary
 

The following summarises current recommendations for assessing the risk of cardiovascular disease (CVD) from the NICE guideline on lipid modification (May 2008):
  • People aged 40–74 years who may be at high risk of CVD should be identified in primary care by estimating their CVD risk from existing medical record data. People should be prioritised in descending order of risk and offered a formal risk assessment if their estimated 10-year CVD risk is 20% or more.

  • Ten-year CVD risk should be formally assessed by means of a Framingham-based scoring system that takes into account age, sex, systolic blood pressure, total cholesterol, high-density lipoprotein (HDL) cholesterol, smoking status and the presence of left ventricular hypertrophy. The formally calculated CVD risk should be multiplied by 1.4 for South Asian men and by 1.5 in people with a first-degree relative with a history of premature coronary heart disease (CHD). Premature is defined as age at onset younger than 55 years in fathers, sons or brothers or younger than 65 years in mothers, daughters or sisters.

  • The formally calculated CVD risk should be multiplied by a factor between 1.5 and 2 if more than one first-degree relative has a history of premature CHD.

  • People who are assessed to have a 10-year CVD risk of 20% or more should be offered lifestyle advice and treatments to reduce their risk.

  • Remember that risk estimation tools only provide an approximation of CVD risk and should be used together with clinical judgment to guide management. Many other factors that may predispose to CVD risk, which are not included in the Framingham risk equation, also need to be considered when deciding if drug treatment is necessary. This is particularly the case where the estimated 10-year CVD risk is near to the 20% threshold. These factors include socioeconomic status, obesity, recent smoking cessation and existing antihypertensive/lipid-lowering treatments. Recognising these limitations, NICE recommends further urgent research and reconsideration of two alternative scoring systems (QRISK, ASSIGN).

  • Formal risk assessment is inappropriate for people with existing CVD or who are at high risk of CVD by virtue of their medical condition (e.g. familial lipid disorders, diabetes). For the small proportion of people with type 2 diabetes who are not already at high risk, the NICE guideline for the management of type 2 diabetes recommends that the UKPDS risk engine can be used for assessing CVD risk.

  • People should be offered information about their absolute risk of CVD and about the absolute benefits and harms of an intervention over a 10-year period. This information should be in a form that presents individualised risk and benefit scenarios, presents the absolute risk of events numerically, and uses appropriate diagrams and text to aid patient understanding. NICE refers people to NPCi (www.npci.org.uk) for further information in this area. The patient decision aid to assist in communicating the risk and benefits of statins is a key resource.

Why is CVD risk assessment important?

Cardiovascular disease (CVD), mainly coronary heart disease (CHD) and stroke, is a leading cause of premature death and morbidity in the UK1-3 and is associated with high NHS costs (£15.7 billion in 2004).4

Significant improvements in the prevention and treatment of CVD have been achieved since the introduction of the National Service Framework for CHD in 2000.5 However, there is still scope for further clinical and cost benefits by identifying those people without CVD who are at risk of developing it and providing them with individually tailored management to reduce their risk of premature death or disability.3

See the Cardiovascular floor of NPCi (www.npci.org.uk) for further information.

Who benefits most from CVD risk reduction?

In the general population most cardiovascular (CV) events occur in people who are not at high CVD risk. Public health measures (e.g. to reduce smoking and consumption of salt and saturated fat, and increase physical activity) are therefore an important component of the national strategy for prevention of CVD.6 However, the higher the CVD risk the greater the potential absolute benefit that a person will derive from a particular intervention. This is because relative risk reductions achieved with interventions to reduce risk, such as statins, are broadly similar regardless of the pre-treatment (baseline) level of risk.7,8

CVD risk assessment is unnecessary in patients with existing CVD, and is inappropriate for people considered at high CVD risk because of an underlying medical condition (e.g. diabetes, familial lipid disorders)8,9 or their age. People who are aged 75 years or older should be considered at increased CVD risk, particularly if they smoke or have raised blood pressure.9

For people without established CVD, recent UK clinical guidelines recognise the importance of using interventions (drugs and lifestyle) to reduce CVD risk in those who are at high risk.8,9

What is meant by high risk?

Clearly, any threshold of CVD risk chosen to establish qualification for treatment is somewhat arbitrary, and represents a balance between probable clinical benefit (e.g. CV events avoided), harms (e.g. adverse drug effects) and affordability. The threshold set in recent UK guidance above which drug treatments should be considered to reduce CVD risk is a 20% risk of suffering CVD‡ over 10 years.8,9

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Single or multiple risk factors for assessing CVD risk?

Compared with multifactor CVD risk prediction estimates, individual risk factors, such as high blood pressure or blood lipid levels, are poor predictors of a patient’s CVD risk and are also poor predictors of a patient’s potential to benefit from treatment.7 Therefore, risk scoring systems, which provide a prediction of a person’s overall CVD risk based on consideration of multiple risk factors, are now recommended in guidelines for prevention of CVD in the UK8,9 and the rest of the world.10

Which CVD risk assessment tool should be used?

A number of risk scoring systems have been devised for estimating CVD risk in clinical practice.6 Those based on equations developed from the Framingham Heart Study have been most widely used. However, estimates of risk using Framingham-based equations reflect the higher risks of CVD in the 1970s and 1980s, and are based on a North American cohort. Although they offer reasonable discrimination between people at high or low risk, they do not include all identified risk factors. Overall, they are likely to overestimate risk in the current UK population, and more so in Southern England than in Northern England and Scotland.6

ASSIGN (www.assign-score.com)11 and QRISK (www.qrisk.org)12-14 are alternative computer-based risk scoring systems developed from UK cohorts. These scoring systems, like Framingham-based systems, include consideration of blood pressure, gender, age and cholesterol levels (total and high-density lipoprotein [HDL] cholesterol). However, unlike Framingham-based systems, they also consider other important risk factors, including socio-economic status and family history of CVD.

As there was insufficient evidence and validation to recommend QRISK or ASSIGN, NICE chose a system based on the Framingham 1991 10-year risk equation15 with which there was considerable previous experience, the limitations of which were well understood.6 NICE advised consideration and/or adjustment of the estimated risk to take account of many of the additional factors (included in ASSIGN and/or QRISK) not considered in Framingham scoring systems (see Panel).6

In view of the recognised limitations of Framingham, NICE made research recommendations to urgently assess whether QRISK or ASSIGN would be more appropriate for use in England and Wales. Since publication of the guideline, a revised version of QRISK (QRISK2), based on data from 2.3 million people in England and Wales, has been developed and validated, and is reported to be more accurate than Framingham for predicting the people who are at high risk of CVD (see http://www.npci.org.uk/blog/?p=169).14 In addition to those factors considered by Framingham-based systems, QRISK2 also considers ethnicity, treated hypertension, social deprivation, body mass index (BMI), family history of CVD, and other medical conditions that might increase CVD risk i.e. atrial fibrillation, type 2 diabetes, chronic kidney disease and rheumatoid arthritis.14 If there are any changes to NICE guidance resulting from this research, this will be the subject of future MeReC outputs.

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How do I identify people for formal risk assessment?

The NICE clinical guideline on lipid modification recommends identification of people aged 40–74 years who are likely to be at high risk of CVD through a systematic, screening process.9 Opportunistic assessment in unselected people is not recommended as the main strategy. An estimate of CVD risk should be calculated using data already recorded in electronic medical records.9 For this purpose, default, best-estimate values can be made where data on risk factors (e.g. for blood pressure, lipid levels) are missing.16 People should be prioritised, in descending order of CVD risk, for a full formal risk assessment if their estimated 10-year risk of CVD is 20% or more.9 Healthcare professionals should discuss the process of risk assessment with the person identified as being at risk, including the option of declining any formal risk assessment.9 People older than 40 years should have their estimate of CVD risk reviewed on an ongoing basis.9

How do I carry out a formal risk assessment?

Full formal risk assessment should be carried out as detailed in the Panel. An example of a suitable Framingham-based risk assessment tool is available online at www.patient.co.uk/showdoc/40000133.

CVD risk estimation tools provide only an approximation of CVD risk to guide management. Also, interpretation of CVD scores should always reflect informed clinical judgement.9 Individual patient circumstances and preferences should always be taken into account when deciding whether or not to prescribe drugs to reduce risk, following full explanation of the likely risks and benefits of treatment. Other factors that may predispose the person to premature CVD, but are not included in the calculated risk scores, should also be considered, especially if the estimate is close to the 20% threshold.9

Should I use a risk calculator for people with type 2 diabetes?

NICE guidance for the management of type 2 diabetes recommends that the UKPDS risk engine (www.dtu.ox.ac.uk/index.php?maindoc=/riskengine) should be used for assessing the CVD risk (annually) for the small proportion of patients who are not already considered to be at high risk, i.e. those who are not overweight, do not have high blood pressure (>140/80mmHg without antihypertensives), do not have microalbuminuria or a high-risk lipid profile, do not smoke, or do not have a personal or family history of CVD.17

How do I communicate risk to patients?

People vary in what they consider to be an acceptable risk. For patients who are at very high CVD risk the decision to take drugs to lower their CVD risk may seem straightforward. However, some patients may not consider that the likely reduction in their risk of having a heart attack or stroke is sufficient to outweigh the risk of adverse effects from taking the drugs for the rest of their lives.

Good communication between healthcare professionals and patients is essential and should be supported by evidence-based written information tailored to the patient’s needs.9 In order to make an informed decision of whether or not to undergo a particular treatment, people need to be provided with information, in an easily understood form, on their current risk and the likely benefits and harms arising from interventions to reduce their risk.18

People should be offered information about their absolute risk of CVD and about the absolute benefits and harms of an intervention over a 10-year period. This information should be in a form that presents individualised risk and benefit scenarios, presents the absolute risk of events numerically, and uses appropriate diagrams and text.9,18,19 NICE refers people to the National Prescribing Centre NPCi website (www.npci.org.uk) for this information (see the Patient Decision Aids room on the Information Mastery 2 floor, and patient decision aids, which are available for specific therapeutic topics within their respective floors on NPCi. The patient decision aid to assist in communicating the risk and benefits of statins can be found at www.npci.org.uk/therapeutics/cardio/cdlipids/patient_decision_aids/patient_decision_aid1.php.

It is important that the information is provided without framing, i.e. giving both positive and negative outcomes in a manner that is unlikely to influence the decision one way or another.18,19 For example, consider these two ways of informing a patient who has a 20% 10-year CVD risk of the benefits of taking a statin (assuming the relative risk reduction for CVD events with a statin is 30%):

  1. Without any treatment there is a one in five chance of you having a heart attack or stroke in the next 10 years. However, I can reduce your risk of having a heart attack or stroke by 30% if I prescribe you a statin.
  2. For every 100 people like you, about 20 will have a heart attack or stroke in the next 10 years, but 80 people will not. If all the 100 people took a statin for 10 years, 14 will still have a heart attack or stroke, regardless of whether they take the statin or not. However, for six of the 100 people, taking a statin will prevent them from having a heart attack or stroke. I can’t tell you if you are one of the six people who will gain a benefit from taking the statin or not, or one of the 94 people who will take a statin for ten years and not get any benefit.

Both are accurate, but the first is framed in a manner that could encourage choice of a statin. The second expresses risk reduction in absolute values, and, although indicating that some people will gain a benefit from taking a statin, it also points out that the outcome for most people will be the same. However, this second example is more detailed and may take some time to digest and understand.

Panel: Full formal risk assessment of CVD risk using the Framingham risk equation9


Formal risk assessment should not be used for people with pre-existing CVD, or for people who are considered at high risk of CVD because of familial hypercholesterolaemia or other monogenetic disorders of lipid metabolism, or diabetes (the UKPDS risk engine can be used for people with type 2 diabetes who are not considered at high risk).

Formal estimation should consider age, sex, systolic blood pressure (mean of previous two systolic readings), total cholesterol, HDL cholesterol, smoking status and presence of left ventricular hypertrophy.

Be aware that the risk equation may overestimate risk in the UK population.

When using the risk score to inform drug treatment decisions, particularly if it is near to the threshold of 20%, consider other factors that may predispose the person to premature CVD, and may not be included in calculated risk scores.

Ethnicity, BMI and family history of premature heart disease should be routinely recorded in medical records.

The estimated CVD risk should be increased by a factor of :
– 1.5 in people with a first-degree relative with a history of premature CHD (age at onset younger than 55 in fathers, sons or brothers or younger than 65 in mothers, daughters or sisters)
– 1.5–2.0 if more than one first-degree relative has a history of premature CHD
–1.4 in men of South Asian background.


Socioeconomic status and severe obesity (BMI >40kg/m2) affects CVD risk and should be considered when using risk scores to inform treatment decisions.

CVD risk may be underestimated in people who are already taking antihypertensive or lipid modification therapy, or who have recently stopped smoking. Clinical judgement should be used to decide on further treatment of risk factors in people who are below the 20% CVD risk threshold.

CVD risk scores may not be appropriate as a way of assessing risk in people who are at increased CVD risk because of underlying medical conditions or treatments. These include people treated for HIV or with antipsychotic medication, people with chronic kidney disease, and people with autoimmune disorders such as systemic lupus erythematosus (SLE) and rheumatoid arthritis.

People aged 75 or older should be considered at increased risk of CVD, particularly if they smoke or have raised blood pressure. Assessment and treatment should be guided by the benefits and risks of treatment, informed preference and comorbidities that may make treatment inappropriate.

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References

  1. Scarborough P, Allender S, Peto V, et al. Regional and social differences in coronary heart disease. 2008. British Heart Foundation: London. Accessed from www.heartstats.org/datapage.asp?id= 7197 on 11/07/08

  2. Allender S, Peto V, Scarborough P, et al. Coronary heart disease statistics. 2007. British Heart Foundation: London. Accessed from www.heartstat.org/datapage.asp?id=6799 on 11/07/08

  3. Department of Health Vascular Programme. Putting prevention first. Vascular checks: risk assessment and management. April 2008. Accessed from www.dh.gov.uk/en/Publicationsandstatistics/Publications/Publications  PolicyAndGuidance/DH_083822 on 11/07/08

  4. Luengo-Fernández R, Leal J, Gray A, et al. Cost of cardiovascular diseases in the United Kingdom. Heart 2006;92:1384–9

  5. Department of Health Coronary Heart Disease Policy Team. The Coronary Heart Disease National Service Framework. Building for the future. Progress report for 2007. Gateway ref: 9423. February 2008. Accessed from www.dh.gov.uk/en/Publicationsandstatistics/Publications/Publications PolicyAndGuidance/DH_083060 on 11/06/08

  6. National Collaborating Centre for Primary Care and the Royal College of General Practitioners. Lipid modification: cardiovascular risk assessment and the modification of blood lipids for the primary and secondary prevention of cardiovascular disease. Full guideline. May 2008. Accessed from www.nice.org.uk/nicemedia/pdf/CG67FullGuideline1.pdf on 11/07/08

  7. Jackson R, Lawes C, Bennett D, et al. Treatment with drugs to lower blood pressure and blood cholesterol based on individual’s absolute cardiovascular risk. Lancet 2005;365:434–41

  8. Scottish Intercollegiate Guidelines Network. Risk estimation and the prevention of cardiovascular disease. A national clinical guideline. No. 97 February 2007. Accessed from www.sign.ac.uk/pdf/sign97.pdf on 11/07/08

  9. National Institute for Health and Clinical Excellence. Lipid modification. Cardiovascular risk assessment: the modification of blood lipids for the primary and secondary prevention of cardiovascular disease. Clinical Guideline 67. May 2008. Accessed from www.nice.org.uk/nicemedia/pdf/CG67NICEguideline.pdf on 11/07/08

  10. World Health Organization. Prevention of cardiovascular disease. Guidelines for assessment and management of cardiovascular risk. 2007. Accessed from www.who.int/cardiovascular_diseases/guidelines/Prevention_of_Cardiovascular_Disease/en/ on 11/07/08

  11. Woodward M, Brindle P, Tunstall-Pedoe H, et al. Adding social deprivation and family history to cardiovascular risk assessment: the ASSIGN score from the Scottish Heart Health Extended Cohort (SHHEC). Heart 2007;93:172–6

  12. Hippisley-Cox J, Coupland C, Vinogradova Y, et al. Derivation and validation of QRISK, a new cardiovascular disease risk score for the United Kingdom: prospective open cohort study. BMJ 2007;335:136, doi:10.1136/bmj.39261.471806.55

  13. Hippisley-Cox J, Coupland C, Vinogradova Y, et al. Performance of the QRISK cardiovascular risk prediction algorithm in an independent UK sample of patients from general practice: a validation study. Heart 2008;94:34–9

  14. Hippisley-Cox J, Coupland C, Vinogradova Y, et al. Predicting cardiovascular risk in England and Wales: prospective derivation and validation of QRISK2. BMJ published online 23rd June 2008; doi: 10.1136/bmj.39609.449676.25

  15. Anderson KM, Odell PM, Wilson PW, et al. Cardiovascular disease risk profiles. Am Heart J 1991;121:293–8

  16. Marshall T. Identification of patients for clinical risk assessment by prediction of cardiovascular risk using default risk factor values. BMC Public Health 2008;8:25. Published online January 23 doi: 10.1186/1471-2458-8–25

  17. National Institute for Health and Clinical Excellence. Type 2 diabetes (update). The management of type 2 diabetes. Clinical Guideline 66. May 2008. Accessed from www.nice.org.uk/nicemedia/pdf/CG66NICEGuideline.pdf on11/07/08

  18. Paling J. Strategies to help patients to understand risks. BMJ 2003;327:745–8

  19. Edwards A, Elwyn G, Mulley A. Explaining risks: turning numerical data into meaningful pictures. BMJ 2002; 324:827–30

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