Absolute cardiovascular risk in clinical practice

• Use absolute risk to calculate CVD risk in the next 5 years for adults aged from 45 years (or 35 years for Aboriginal and Torres Strait Islanders).
  
• Not all adults will need absolute risk calculated as they may already be at clinically determined high risk of CVD.
  
• Clinical judgement remains a key requirement when assessing absolute risk, especially for specific populations.
  
• Aboriginal and Torres Strait Islanders people >74 years are clinically determined high risk.
  

Absolute CVD risk assessment describes the likelihood (expressed as a percentage) that an individual will experience a CV event within a given time period (usually 5 or 10 years).^{1, 2}

Australian guidelines calculate absolute risk using an equation model based on data from the long-running Framingham Study.¹ This risk equation accounts for several contributors to cardiovascular disease in an individual, has been validated in non-Indigenous Australian adults and categorises absolute risk as low (<10% likelihood of CVD event over 5 years), moderate (10–15%) or high (> 15%).¹

In adults, assess absolute cardiovascular risk from 45 years (or 35 years for Aboriginal and Torres Strait Islanders) according to the algorithm below.¹ 

Be aware that there are parameters defining appropriate use of this assessment tool within clinical practice, especially for use in populations not represented in the Framingham study (e.g. older people > 74 years, Aboriginal and Torres Islander peoples).

Absolute risk calculator is only applicable for primary prevention

Absolute risk calculators are useful for measuring risk in asymptomatic patients without CVD (ie primary prevention).¹ The calculators have not been validated for use in people with established CVD (ie, coronary heart disease, stroke, peripheral arterial disease, some types of kidney disease) who should be treated as high risk and managed accordingly

Some patients without CVD are automatically determined as high risk

Not all individuals need a formal absolute CVD risk calculation (regardless of their age) because they are already clinically determined to be at high risk of a cardiovascular event.¹ This group includes those with:

• diabetes and age 60 years
• diabetes with microalbuminuria (20 micrograms/min or urinary albumin:creatinine ratio;2.5 mg/mmol for males, 3.5 mg/mmol for females)
• moderate or severe chronic kidney disease (eGFR 45 mL/min/1.73 m2)
• previous diagnosis of familial hypercholesterolaemia
• systolic BP ≥180 mm Hg; or diastolic BP ≥ 110 mm Hg
• serum total cholesterol 7.5 mmol/L
• Aboriginal and Torres Strait Islander adults aged over 74 years

Absolute risk equations underestimate risk in certain groups

Some patients carry risk factors that can impact on CVD but have not been included within the current absolute risk equation. Other patients belong to populations that are outside those upon which the risk models are based.^3-5

As a result, using absolute risk can be somewhat limited and may represent only part of the risk estimate (eg, underestimate risk). In many of these patients absolute risk assessments can be taken as a good estimate of the minimum risk and interpretation of risk with subsequent treatment decisions needing to be guided by clinical judgement.¹ For example, in overweight or obese patients not at calculated high risk, consider measuring waist circumference and use this to further inform risk level (eg, risk is increased at ≥ 80 cm and high at ≥ 88 cm for women, and increased at ≥ 94 cm and high at ≥ 102 cm for men). ^1,6 Be aware these cutoffs vary according to ethnic backgroup of the individual. More information can be found in the NHMRC Clinical practice guidelines for the management of overweight and obesity in adults, adolescents and children in Australia.

The absolute risk equation currently used in Australia may underestimate CVD risk in:¹

• Adults of Aboriginal and Torres Strait Islander descent
• Adults of South Asian, Maori, Pacific Islander and Middle Eastern descent
• Adults with diabetes
• Adults aged over 74 years
• Adults with socioeconomic disadvantage
• Adults with depression

Use pre-treatment measurements for patients already receiving medication

The Framingham risk equation is designed to calculate risk using measurements obtained before pharmacological treatment.¹ Therefore, the aim is to use the most recently recorded pre-treatment measure to estimate risk. Blood test results within 5 years can be used. If pre-treatment values are not available or considered clinically inappropriate, use on-treatment values recognising that they may underestimate risk.

What about elevated blood pressure in young children, teenagers or younger adults (45 years)?

Confirm high BP using repeated valid BP measurements. Investigate to rule out secondary hypertension.^7,8

• Australian Cardiovascular Disease Risk Charts (external link to Heart Foundation of Australia website).
  
• Online cardiovascular disease risk calculator (external link to www.cvdcheck.org.au).
  
• Quick reference guide to absolute cardiovascular disease risk assessment (external link to www.cvdcheck.org.au).
  
• Full guidelines for the assessment of absolute cardiovascular disease risk  (external link to www.cvdcheck.org.au).