Absolute risk frequently asked questions (FAQs)
Why assess absolute risk?
The absolute risk method has been promoted internationally for many years. This approach moves away from the traditional single risk factor assessment, to a more accurate prediction of an individual’s overall cardiovascular disease risk. By using a more accurate prediction, health providers can make more informed decisions about how to care for their patients. Absolute risk assessment provides a quick and effective way to identify those who are most at risk of cardiovascular disease, and therefore those who can benefit the most from intensive management.
What resources are available on absolute cardiovascular disease (CVD) risk?
The Guidelines for the Management of Absolute Cardiovascular Disease Risk, released in May 2012, incorporates and builds on the previous NVDPA Guidelines for the Assessment of Absolute Cardiovascular Disease Risk (2009) and consolidates a number of other evidence-based guidelines to provide clear guidance to prevent first-ever CVD events. The full management guideline, Quick reference guide for health professionals and consumer resource can be accessed here. The Guidelines for the Assessment of Absolute Cardiovascular Disease Risk (2009) can be downloaded from the National Heart Foundation of Australia's webpage on absolute risk.
For calculation of absolute risk, should current (treated) blood pressure be used or previous (untreated) blood pressure?
The most recently recorded pre-treatment value should ideally be used for individuals taking antihypertensive medication. Where this is not possible decisions about increasing or decreasing therapy should be made with their doctor (rather than calculating risk on treatment).
If a patient has recently stopped smoking (within the last month or so), are they assessed as smokers or non-smokers?
It may take some time for a recent non-smoker to return to a non-smoker level of health, therefore this type of patient should be categorised as smoker in the risk assessment calculation.
If a patient considers themselves ‘transgender’, what gender should be used for absolute risk assessment?
The patient’s birth gender should be used for assessment of absolute CVD risk.
How were the NVDPA Guidelines for absolute cardiovascular disease risk developed?
The absolute risk guidelines were developed according to the standards outlined in the NHMRC Standards and Procedures for Externally Developed Guidelines (2007)
Guidelines for the Assessment of Absolute Cardiovascular Disease Risk:
A systematic review was completed in order to formulate recommendations (using literature up to April 2006). The resulting report, titled Technical report: review of the evidence and evidence-based recommendations for practice is available on NVDPA member websites.
Where the systematic review identified insufficient evidence to answer a clinical question, a consensus-based approach was used to formulate recommendations. A steering group with broad representation completed this. Consensus statements were formulated based on available evidence (using literature up to August 2007) and expert clinical judgement.
Public consultation process to review the full guideline (April-May 2008).
Independent review of the full guideline by the National Health and Medical Research Council (NHMRC) (July-October 2008).
Finalisation of the guideline based on feedback from the review.
Endorsement by the NHMRC, received in January 2009.
Guidelines for the Management of Absolute Cardiovascular Disease Risk:
A systematic literature review was completed to answer pre-defined clinical questions. The search used literature from 2006 to June 2010 for the assessment of CVD risk, and 2002 to June 2010 for the remaining questions relating to management of absolute CVD risk. Hand searching was conducted between June 2010 and May 2011. More information on the search strategy is available in the full guideline.
Where the systematic review identified insufficient evidence to answer a clinical question, a consensus-based approach was used to formulate recommendations. A steering group with broad representation completed this. Consensus statements were formulated based on available evidence and expert clinical judgement.
The public consultation process invited feedback during a month-long period in April 2011. A broad group of stakeholders, networks and consumer organisations were also invited to comment.
Independent review of the full guideline by the National Health and Medical Research council (NHMRC).
Endorsement by RACGP and NHMRC, received in April 2012.
What are the absolute risk web calculator and paper-based risk charts based on?
The absolute risk calculator and risk charts are based on the prediction equation known as the Framingham Risk Equation. This equation has been tested for its validity and has shown to have good predictive ability. The systematic reviews for both the assessment and management guidelines compared the predictive ability of different absolute cardiovascular disease risk assessment methods. The reviews found that the Framingham Risk Equation was the most thoroughly tested method of assessing absolute cardiovascular risk (in adults not known to have diabetes or existing cardiovascular disease) and had higher or equivalent predictive ability compared with other absolute cardiovascular disease risk assessment methods.
For more detailed information see Chapter 1 of the NVDPA Guidelines for the Management of Cardiovascular Disease Risk.
What is the Framingham Risk Equation?
The Framingham Risk Equation is a predictive equation borne out of the Framingham Heart Study, which started in 1948 and has been operational for more than 60 years. You can read about the Framingham Heart Study by clicking here.
The Framingham Risk Equation was developed for several cardiovascular disease endpoints by Anderson and colleagues in 1991. The citations for the relevant scientific papers are:
The Framingham Risk Equation that the NVDPA web calculator and paper-based risk charts are based on can be viewed in Appendix IV (page 113) of the systematic review report Technical report: review of the evidence and evidence-based recommendations for practice.
How is absolute risk different to relative risk?
Absolute risk is a method of determining an individual’s overall heart and stroke risk level over a defined time period (for example, 5 or 10 years). In the NVDPA guidelines, absolute risk is defined as the chance of an individual experiencing a cardiovascular event (including a heart attack or stroke), over a 5 year period, expressed as a percentage.
In contrast, relative risk is a ratio of the rate of events in the population exposed to a risk factor compared with the rate among the population not exposed to this risk factor. It tells you little about an individual’s actual risk over time. Management that is based on absolute risk has the potential to deliver treatments to those who can benefit the most, because absolute risk is a more meaningful way of measuring a person’s actual risk.
Why are some cardiovascular disease risk factors, such as family history, not included in the assessment?
Some well known risk factors for cardiovascular disease, such as obesity, are not included in the risk calculations. This is not because they are not important for reducing cardiovascular disease risk, but because either research showed that they did not increase the predictive value of the final equation, or the Framingham Risk Equation has not been specifically assessed in these populations (e.g. the overweight and obese).
Nevertheless, the guidelines do recognise that consideration of these factors is important when completing a comprehensive assessment of absolute risk. The guidelines recommend that a comprehensive risk assessment include:
those factors assessed in the risk calculator, as well as
consideration of other issues such as the patient's socioeconomic status, family history, cultural and ethnic identity, waist circumference, body mass index, nutrition, alcohol intake, physical activity level and any other related conditions (kidney function, familial hypercholesterolaemia, and atrial fibrillation).
How should the absolute risk score be interpreted for diverse ethnic groups?
The Framingham Risk Equation has not been specifically assessed across diverse populations. The NVDPA does recognise that consideration of this is important when completing a comprehensive assessment of absolute risk.
Why isn’t diastolic blood pressure used in the absolute risk calculator?
The absolute risk calculator is based on the Framingham Risk Equation. Separate Framingham equations were developed for use of systolic blood pressure and diastolic blood pressure. Except for the blood pressure covariate, the models are identical for both blood pressures and for most outcomes differences in predictive probabilities are slight. However, because the log likelihoods are slightly higher when systolic blood pressure is used, it has been recommended by Anderson et al. (1991) that systolic blood pressure be used where possible.
What are the differences between the Australian risk charts and the NZ risk charts?
While both the Australian and New Zealand risk charts are based on the Framingham Risk Equation, you will see some differences in the Australian charts, including:
The charts include values for systolic blood pressure up to 179 mmHg, rather than 180 mmHg. This is because individuals with a systolic blood pressure of 180 mmHg or more should be considered at increased absolute risk of cardiovascular disease and do not require risk calculation using the risk charts.
A footnote has been added indicating that individuals with a total cholesterol level greater than 7.5 mmol/L should be considered at increased absolute risk of cardiovascular disease and do not require risk calculation using the risk charts.
The charts are categorised by diabetes status, rather than sex.
A note has been added that individuals with diabetes and age over 60 should be considered at increased absolute risk of cardiovascular disease and do not require risk calculation using the risk charts.
Now that I’ve assessed absolute risk, how do I manage it?
The NVDPA Guideline for the Management of Absolute Cardiovascular Disease Risk provides the recommended assessment pathway, interventions, targets and follow-up. It incorporates the recommendations from the assessment guidelines and consolidates recommendations for lifestyle and drug therapy for cholesterol and blood pressure lowering into a single guideline.
The full guideline, Quick reference guide for health professionals, and consumer resource can be accessed here.