Heart and vessels
Apolipoproteïne A2
The second protein of HDL cholesterol; its significance for the risk of cardiovascular disease is unclear.
Everything about this testWhat it measures
Cholesterol and other fats travel through the blood in small spheres called lipoproteins. The proteins on these spheres are called apolipoproteins. HDL, the particle that brings cholesterol from the blood vessel wall back to the liver, mainly carries apolipoprotein A1 and, in addition, apolipoprotein A2. Apolipoprotein A2 is therefore the second most important protein of HDL. Exactly what role it plays in removing cholesterol and in inflammation is not yet well known.
- An indication of the amount and composition of HDL particles
- Rarely: a rare inherited disorder of HDL metabolism
High
A high value usually goes together with a high HDL cholesterol. Alcohol use and some medicines, such as estrogens and anti-epileptic drugs, can also raise the value. Whether a high value is favorable or unfavorable for the risk of cardiovascular disease is not clear; studies contradict each other. A high value causes no symptoms.
Low
A low value usually goes together with a low HDL cholesterol, as with smoking, overweight, little exercise, diabetes or a high triglyceride level. Rarely, a very low value fits an inherited disorder of HDL metabolism. A low value causes no symptoms itself; what counts for the risk of cardiovascular disease is mainly LDL or non-HDL cholesterol and the other risk factors.
If your result is abnormal
An abnormal value on its own usually does not lead to follow-up. The GP looks at the full cholesterol test and the other risk factors and, with an increased risk, follows the Dutch GP guideline (NHG) on cardiovascular risk management. With a very low HDL cholesterol without explanation, referral to an internist (specialist in internal medicine) may follow.
Reliability
What an abnormal apolipoprotein A2 means for the risk of cardiovascular disease has been little studied, and the findings are contradictory. There are no agreed cut-off values. According to the Dutch Society for Clinical Chemistry (NVKC), even apolipoproteins A1 and B add something to HDL and LDL cholesterol at most in complex cases; even less is known about A2. For the risk estimate according to the Dutch GP guideline (NHG) on cardiovascular risk management, age, blood pressure, smoking and non-HDL cholesterol say much more.
Limitations
- Alcohol, estrogens (including the contraceptive pill) and some anti-epileptic drugs raise the value.
- The value largely follows HDL cholesterol and adds little information to it.
- Measurement methods and reference values differ per laboratory and are not well standardized.
How common is this
There are no Dutch figures on how often an abnormal apolipoprotein A2 occurs, because the test has no agreed cut-off values. Cardiovascular disease itself is common in the Netherlands and is one of the main causes of death.
Who is this useful for
The result says little in people without symptoms, and in estimating the risk of cardiovascular disease it also adds little to standard cholesterol testing. It can be meaningful when a rare inherited disorder of HDL metabolism is suspected, for example with a very low HDL cholesterol in the family.
Downsides and risks
- An abnormal value without a fixed meaning can cause unnecessary worry or lead to unnecessary follow-up testing.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results