In March 2009, the National Vascular Disease Prevention Alliance (NVDPA), a consortium of Diabetes Australia, Kidney Health Australia, the National Heart Foundation of Australia, and the National Stroke Foundation, released evidence-based guidelines for assessing absolute cardiovascular risk.1 The guidelines are for use by health professionals who assess patients’ cardiovascular risk, primarily general practitioners. The risk charts that accompany the guidelines differ somewhat from the New Zealand risk charts,2 which are commonly used in Australia. Both the Australian and NZ charts are based on the Framingham Heart Study.3 The Australian cardiovascular risk charts are separated at the broader level into people with and without diabetes, rather than into men and women. In addition, systolic, but not diastolic, blood pressure is included because it is the stronger determinant of future events. The charts extend to upper cut-off points of 179 mmHg for systolic blood pressure and 7.5 mmol/L for total cholesterol level, respectively. The NVDPA guidelines also have an online risk calculator (http://www.cvdcheck.org.au). The new NVDPA guidelines and charts have the advantage of taking into account other drivers of practice in Australia, such as the Royal Australian College of General Practitioners’ Guidelines for preventive activities in general practice,4 and eligibility for Pharmaceutical Benefits Scheme subsidies for statins.

Absolute risk assessment maximises the effectiveness of prediction of risk of future cardiovascular disease (CVD) events in people apparently free of such disease. This is because the underlying equations acknowledge fundamental epidemiological principles: risk depends on the range of independent risk factors and, for biomedical factors, risk typically increases in a log–linear manner above ideal levels (systolic blood pressure and total cholesterol level, 115 mmHg and 3.8 mmol/L, respectively).5 The present, somewhat arbitrary, definitions of hypertension and hypercholesterolaemia as ≥ 140/90 mmHg and ≥ 5.5 mmol/L, respectively, are fundamentally flawed, and most people who have CVD events have a clustering of risk factors with only modest abnormalities. If relative risk reduction with an intervention is relatively constant (the usual case), use of the intervention in those at higher absolute risk leads to greater absolute risk reduction and net benefit, thus also maximising cost-effectiveness.

All absolute risk tools share some problems. As they are derived from large population studies, they are better at rank-ordering risk in subgroups and less precise in an individual. However, individual risk assessment may be refined (particularly in those initially assessed to be at intermediate risk) by measuring biomarkers or by imaging,6 and probably more so in the future, as more evidence becomes available. Other factors that might also be added to future algorithms include anthropometric measures (of these, waist circumference or waist : hip ratio appears more predictive than body mass index), a family history of premature atherosclerotic disease, and measures of socioeconomic deprivation.7 The NVDPA guidelines acknowledge that the Framingham risk equation may underestimate risk if these factors are present. The major determinant of CVD risk is increasing age, and it is also likely that equations specific for various age groups will become available. Particularly among younger people, this will improve identification of those with greater modifiable risk.

Ideally, risk equations should be developed and validated in the local population. In Australia, algorithms for the general population have been developed from the Busselton8 and Dubbo9 studies. These are important contributions, although the relatively narrow endpoint (in Busselton) and the cohort age (in Dubbo) limit their application.

How best can the NVDPA tools be used by practising clinicians? The first step is to identify high-risk groups. These include people with one or more of the following: prior CVD events, peripheral arterial disease, diabetes and age ≥ 60 years, chronic kidney disease, and familial hypercholesterolaemia. Such people should be treated accordingly and do not need absolute risk assessment. In all others, absolute risk assessments should commence at age 45 years, or 35 years for Aboriginal and Torres Strait Islander people, and be repeated at intervals reflecting the initial level of risk.1 An example of how to incorporate absolute cardiovascular risk assessment into management is given in the Box.

What we now need is a robust implementation program. This makes economic sense. Recently, the National Health Service Health Check program was released in the United Kingdom.10 Everyone between 40 and 74 years, not already diagnosed with heart disease, stroke or kidney disease, will be invited, once every 5 years, to have their risk assessed using an absolute risk tool, and given support and advice to help them reduce or manage their risk. Analyses showed that this program would be very cost-effective compared with other accepted health interventions. The modelled cost-effectiveness ratio of this UK program is only £2480 per quality-adjusted life-year gained.

Presently, in Australia, a Medicare item number supports a single health check for those aged 45–49 years. Although cost-effectiveness analyses are sensitive to the local health care system, the UK data strongly suggest that the current Medicare item number could be expanded, and other systems-based approaches implemented, to ensure that ongoing primary care risk assessments are supported, and that people at higher risk receive lifestyle and appropriate medical management. Implementation would be most likely to be effective if decision-support tools and recall mechanisms were used and incorporated into prescribing linked to electronic health records. Accompanying materials that appropriately communicate concepts of risk to patients would also be useful. The NVDPA is now developing a single CVD risk-management guide that will integrate the various specific risk-factor guides and make it easier to manage patients according to their absolute risk status.

Absolute risk assessment does not replace the need to base all approaches to CVD prevention on lifestyle change. Studies have clearly shown the value of this, whether or not individuals are receiving blood-pressure or lipid-lowering therapies.11 However, absolute risk assessment leaves behind time-hallowed approaches based on individual risk factors, treated in silos, and often “dichotomised” to be regarded as “normal” or “abnormal”. It moves us forward to a more rational and effective paradigm for preventing our major health problem.

How to incorporate absolute risk assessment into management using the Australian cardiovascular risk charts (the “People without diabetes” section of the charts is reproduced below)

Example: Two women with similar risk profiles, but different ages

Both women are smokers, without diabetes, with systolic blood pressure, 140 mmHg; total cholesterol : high-density lipoprotein cholesterol (TC : HDL) ratio, 7.2 mmol/L; and body mass index, 27 kg/m2.

A is 46 years old and estimated to have a low risk (5%–9%) of developing cardiovascular disease (CVD) within 5 years. However, if she continues to smoke and to have a high TC : HDL ratio, she will place herself at high risk of prematurely developing CVD as she gets older. The chart can be used to demonstrate this to her. The priority intervention should be lifestyle advice, including smoking cessation, physical activity and healthy eating.

B is 66 years old and estimated to be at high risk (20%–24%) of having a CVD event within 5 years. As a high priority, she should receive advice about smoking cessation and other lifestyle changes, as well as statin therapy.

How to use the risk chart

1. Identify the chart relating to the person’s sex, diabetes status, smoking history and age. The charts should be used for all adults aged 45–74 years (and all Aboriginal and Torres Strait Islander adults aged 35 years or older) without known history of CVD or already known to be at high risk.
2. Within the chart, choose the cell nearest to the person’s age, systolic blood pressure (SBP) and total cholesterol (TC):HDL ratio. For example, the lower left cell contains all non-smokers without diabetes who are 35–44 years and have a TC:HDL ratio of less than 4.5 and a SBP of less than 130 mm Hg.
3. The colour of the cell that the person falls into provides their 5-year absolute cardiovascular risk level (see legend above for risk category). People who fall exactly on a threshold between cells are placed in the cell indicating higher risk.

Charts are based on the NVDPA’s Guidelines for the assessment of absolute cardiovascular disease risk and adapted with permission from New Zealand Guidelines Group. New Zealand Cardiovascular Guidelines Handbook: A Summary Resource for Primary Care Practitioners. Second edition. Wellington, NZ: 2009. www.nzgg.org.nz.

---

These charts are taken from Absolute cardiovascular disease risk assessment – quick reference guide for health professionals. © 2009 National Heart Foundation of Australia. Reproduced with permission. No further reproduction is allowed.