A cholesterol test measures the total amount of cholesterol in your blood. It is often performed as part of a screening test called a Lipid Panel which is most often used to assess your risk of developing heart disease or stroke. It measures levels of cholesterol, LDL or low-density lipoprotein cholesterol and HDL or high-density lipoprotein cholesterol. Triglycerides, another form of fat, is also measured.
A higher than normal LDL often called "bad" cholesterol level is one of the most important modifiable risk factors for diseases of the blood vessels and your risk of having a stroke or heart attack. These conditions are known together as cardiovascular disease (CVD).
Over the years, many clinical trials have demonstrated that lowering LDL cholesterol in people with higher levels reduces the risk of having a stroke or heart attack in people with and without CVD.
Your doctor will make a judgement about whether LDL cholesterol lowering treatment should be started depending on your overall CVD risk. This risk calculation includes other CVD risk factors such as high blood pressure, age, diabetes, and smoking. Your heart and stroke risk score can be calculated using the calculator at www.cvdcheck.org.au/calculator.
Why get tested?
Cholesterol tests are blood tests that can help find out if you are at risk of developing heart disease or having a stroke. Your doctor may ask you to be tested if you:
Cholesterol and its role in your health
Cholesterol is a waxy type of fat that performs a range of important functions in the body. We cannot live without cholesterol. It's found in every cell in our body and is involved in a whole host of vital processes. It's so important that the body has developed many complex systems to make sure we have enough. However, high amounts of cholesterol can lead to heart disease or stroke.
Cholesterol sticks together with cells, other fats, calcium and debris that are floating around in the bloodstream to form plaque in the walls of arteries. A cap forms over the soft sticky plaque and if this breaks open say, if your blood pressure spikes a clot can form that blocks the blood flow through the artery. Without blood and the oxygen it carries being able to get to your heart or brain, you can have a heart attack or stroke. The majority of heart attacks occur when small plaques break open.
By reducing cholesterol from the inside of the plaques you can reduce your risk of heart attack or stroke. It's possible to do this by lowering the cholesterol travelling around in your blood.
LDL and HDL and why they are important
Cholesterol is carried around the bloodstream in lipoproteins. There are several types of lipoproteins, but the main ones are High-Density Lipoprotein (HDL) cholesterol sometimes called “good” cholesterol and Low-Density Lipoprotein (LDL) cholesterol or “bad” cholesterol.
All cholesterol is the same - it's the lipoproteins that carry it that are different.
Having the test
In the past, you needed to fast before this test but now it is considered that fasting is not needed — in fact non-fasting is preferred by many laboratories. If you need to repeat a test to confirm abnormal results, fasting for 8 — 12 hours may be required and only water is permitted.
Reading your test report
Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.
Total cholesterol can be measured alone or in combination with HDL-cholesterol, LDL-cholesterol, and triglycerides - often called a Lipid Profile.
If your results are higher than they should be, a second blood sample should be taken on a separate occasion before a definitive diagnosis is made, as levels may vary between tests. Cholesterol levels fluctuate over time. The measured cholesterol level may differ by as much as 10 per cent from one month to another. If you've been following a healthy diet and exercising but your cholesterol levels rise it may be due to these inherent fluctuations. Cholesterol levels measured over several months will give a good picture of the true state of your cholesterol.
Your report may look like this example form. Bear in mind that the format and look of reports vary between laboratories. Note that on this report Paul Harding's Cholesterol and LDL cholesterol have been marked with a H in red to show that they are high.
Your results will be compared to reference intervals (sometimes called a normal range).
If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation. Your results need to be interpreted by your doctor.
Questions to ask your doctor
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:
Any more to know?
About one in 250 people have a genetic predisposition to having high LDL cholesterol which puts them at a greater risk of having heart disease earlier in life. A genetic test for this is now available in Australia through Medicare.
The body's cells, particularly the liver cells, take up LDL cholesterol from the blood via LDL receptors. Normally, a person has two working copies of the gene encoding the LDL receptor (one copy inherited from their mother and one from their father), but in someone with Familial Hypercholesterolaemia (FH) one copy is defective, so only half of the normal numbers of LDL receptors are produced. This results in LDL cholesterol accumulating in blood and artery walls.
A calculated score called the Dutch Lipid Clinic Network Score, based on your family history, untreated LDL cholesterol levels and physical signs, is used to decide whether FH is likely. Your doctor may order a genetic test for FH to confirm a diagnosis. If you are diagnosed with FH it is recommended that your close relatives are also tested.
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