This document was added or updated on 17/07/2015.

ABSOLUTE RISK

Absolute Risk uses a variety of input variables to calculate a risk score, expressed as a percentage, of a person having a cardiovascular event within a 5-year period.

The data items available are:

• Absolute Risk (%) - continuous
• Absolute Risk (Risk of CVD event in next 5 years)
• Absolute Risk Incomplete Data Flag

For the Absolute Risk data item, the following section outlines the:

• definitions used to derive the data item
• population applicable to the data item
• methodology used to produce data item

For information on the data used to derive this item (as outlined below), refer to the relevant topic pages in this Users' Guide.

Definition

For the purposes of deriving this item the following definitions were used:

Diabetes status

Diabetes status was determined based on the Diabetes prevalence - HbA1c (%) data item.

Self reported prior cardiovascular disease

People who reported having had a stroke, heart attack or heart disease were classified as Automatic High Risk - prior CVD. For self reported prior cardiovascular disease, the following conditions were required to have been diagnosed and also be current and long-term (condition status 1):

• Angina
• Other Ischaemic heart diseases
• Heart failure
• Other heart disease
• Stroke
• Other cerebrovascular disease
• Oedema
• Diseases of the arteries, arterioles and capillaries

Incomplete data

People who participated in the Biomedical component but had partial or incomplete results for some of the tests.

Population

The population for this topic are respondents aged 18 years and over who participated in the biomedical component of both the National Aboriginal and Torres Strait Islander Health Survey (NATSIHS) and the National Aboriginal and Torres Strait Islander Nutrition and Physical Activity Survey (NATSINPAS).

Methodology

The calculation for Absolute Risk for the Australian Aboriginal and Torres Strait Islander Health Survey is based on the calculation requirements outlined by the National Vascular Disease Prevention Alliance, with some modifications to account for survey content differences. For more details regarding Absolute Risk calculations, refer to http://www.cvdcheck.org.au/.

Absolute Risk is calculated using a combination of blood test results, demographic information and self reported information on cardiovascular disease. These input factors go into a weighted multiplicative formula to give an Absolute Risk score, expressed as a percentage. The input factors used in the Absolute Risk algorithm are:

• Age
• Sex
• Blood pressure
• Smoking status
• Total cholesterol status
• HDL cholesterol status
• Diabetes status
• ACR status
• eGFR status
• Self reported prior cardiovascular disease

An Aboriginal or Torres Strait Islander person is classified as Automatic High Risk (greater than 15%) if they satisfy any of the following:

• Has reported having a stroke, heart attack or heart disease
• Aged 75 years and over
• Aged 61 years and over and has diabetes
• Has diabetes and microalbuminuria
• Has eGFR levels less than 45 mL/min/1.73m2
• Has systolic blood pressure reading of 180 mmhg or higher
• Has diastolic blood pressure reading of 110 mmgh or higher
• Has total cholesterol level greater than 7.5 mmol/L

Note that if a respondent could be classified into the Automatic High Risk (greater than 15%) and Automatic High Risk - prior CVD, then the Automatic High Risk - prior CVD category took precedence.

A percentage score of Absolute Risk is calculated for those individuals who do not meet any of the criteria for Automatic High Risk, based on these input factors:

• Age
• Sex
• Blood pressure
• Smoking status
• Total cholesterol status
• HDL cholesterol status
• Diabetes status

People who participated in the Biomedical component but had partial or incomplete results for some of the tests will generally be classified as Unable to calculate. However, as a score can still be assigned due to meeting a requirement for the automatic classification to the Automatic High Risk status categories, or using the available components, people with incomplete or missing results can still be assigned a risk score. An Absolute Risk Incomplete Data Flag has been created to remove these people from the calculations if desired.

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