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APOLIPOPROTEIN B (Apo B)

Definition

Apolipoprotein B (Apo B) is primarily the protein component of Low Density Lipoprotein (LDL) cholesterol. Evidence from research suggests that Apo B is the superior indicator of cardiovascular disease (CVD) risk as there is only one Apo B protein found on each LDL particle and it can be measured directly (as opposed to using an equation to determine LDL cholesterol levels).¹ High levels of Apo B may increase the risk of CVD.

The Apo B test measures the amount of Apo B circulating in the blood at the time of the test.

Population

Apo B results were obtained for selected persons aged 12 years and over, who agreed to participate in the National Health Measures Survey (NHMS) and provided a blood sample. Fasting was not required for this test.

Methodology

A blood sample was collected from participants and Apo B levels were measured at the Douglass Hanly Moir (DHM) laboratory.

There is no consensus on the cut off reference values for defining abnormal Apo B for the Australian population, as there are currently a number of different methods that can be used to measure Apo B. As such, laboratory reference ranges, which are based on major clinical trials, have been used in the NHMS. In the NHMS, cut off reference values for normal and abnormal results were sourced from DHM laboratory reference ranges.²

In the NHMS, the following definitions were used for serum Apo B:

	Apo B levels for females (g/L)	Apo B levels for males (g/L)
Normal	≤1.2	≤1.3
Abnormal	>1.2	>1.3

• Apo B results do not confirm a specific diagnosis without consultation with a health professional.
• Age, gender and taking lipid lowering medications are all variables that may affect lipid and lipoprotein levels.³ As a result, the data should be interpreted with care.
• There are a number of different test methods for measuring Apo B, which may produce different results. The data from this topic should therefore be used with caution when comparing Apo B results from other studies using a different test method or equation.
• Persons with a triglyceride level of ≥ 4.5 mmol/L were excluded from the LDL cholesterol data. According to Friedewald et al, the inclusion of triglyceride levels ≥ 4.5 mmol/L (400 mg/100 ml) will result in the generation of a false LDL cholesterol result.⁴ As a result, the lipid guidelines have advised that Apo B levels can be used in place of LDL cholesterol levels to report the prevalence of CVD.⁵
• The Apo B normal and abnormal cut off points are based on Douglass Hanly Moir laboratory reference ranges. These ranges may vary depending on the analytical method and analytical machine, as there is currently no standard method or epidemiological guidelines to report normal and abnormal cut off points for Apo B.
• In the NHMS an upper limit cut off has been reported to differentiate between normal and abnormal Apo B levels.