HDL cholesterol | Pathology Tests Explained

What is being tested?

The HDL cholesterol test measures the amount of cholesterol carried by HDL (high density lipoprotein) particles in the blood. Too much cholesterol in the bloodstream can be damaging if it is deposited in the walls of the blood vessels. However, HDL particles actually remove excess cholesterol from the body. Hence, having a high level of cholesterol carried by HDL particles is generally good and HDL cholesterol is often termed ‘good’ cholesterol.

How is it used?

The test of HDL cholesterol is used to determine your risk of heart disease. If high cholesterol is due to high HDL cholesterol, a person is at lower risk and treatment for high cholesterol may not be advised. HDL cholesterol results are rarely considered in isolation and form part of an overall picture of cardiac risk.

When is it requested?

HDL cholesterol is usually requested with other tests; either with cholesterol or as part of a lipid profile, including LDL cholesterol and triglycerides. The combination of total cholesterol and HDL cholesterol is very useful for screening for the risk of heart disease since it is not necessary to fast for these two tests. In contrast, a more complete lipid profile requires fasting for about 12 hours.

Reading your results

The lipid profile is a group of tests used to assess your risk of cardiovascular diseases (heart disease, stroke and related diseases). It checks total cholesterol, triglycerides, HDL cholesterol and LDL cholesterol. The results are considered along with other important factors such as your age, gender, ethnicity and blood pressure and whether you have diabetes or smoke.

If you’ve had test results for cholesterol and triglycerides, this example form may help you understand them.

Who prepares your test results report?

In this report, four tests have been performed as a group. They each measure a different substance in the blood that can indicate a possible health problem if levels are shown to be too high or too low.

In this example case, the purpose of the first test was to check the lipid profile (cholesterol, triglycerides plus HDL and LDL) of this relatively young man. Normally, this would not be done unless the person has known risk factors. In this case, Paul has a strong family history of early heart disease. His grandfather and two uncles have all died some years ago from heart attacks and recently, his 53-year old father has also had a fatal heart attack. His father had always been apparently healthy and had not had blood tests to check his lipids.

What the results mean?

Two sets of results are shown from tests that have been performed just over two weeks apart.

In the first column of results, showing tests performed on the 28th of February Paul was found to have very high total cholesterol and LDL cholesterol.
The current results (16th March) have been done to confirm the initial results because they were so abnormal and because Paul had been drinking quite heavily prior to the first test. The second set of results are very similar to the first and have not changed after two weeks without alcohol.
The comment on the report states that Paul has a high probability of having familial hypercholesterolaemia. This is an inherited condition in which people have a very high risk of developing early coronary artery disease.
They need to have treatment.
The results have been compared to a reference interval. This is shown on the far right (column 5).
The reference intervals represent the levels of cholesterol and triglycerides which would be considered ‘healthy’ for the general population. (Note that for these two substances, the range given is not the same as most ‘normal’ ranges which are derived from the results for most healthy people. In this case they are derived from studies showing the levels at which the risk of developing early coronary artery or other atherosclerotic disease is acceptably low. Because our modern diet and lifestyle are not ideal, the statistical ‘normal’ ranges would be higher than is desirable.)
If your results are outside this range and flagged with an H (high) or L (low) this is just to draw your attention to them. If the total cholesterol, LDL cholesterol or triglyceride levels are flagged as high this suggests that you and your doctor should discuss strategies to reduce the levels.
Your results need to be interpreted by your doctor who will consider them in the context of your whole medical history, as well as the results of any other investigations you have had.
There are a number of other causes of high cholesterol results and also high triglyceride results. You should also look at the entry for lipid profile.

Who prepares your test results report?

Your tests will have been performed by scientists and/or pathologists (who are medical doctors). The pathologist-in-charge who specialises in interpreting test results and observing and evaluating biological changes to make a diagnosis, will be responsible for your report. The pathologist is also available to discuss your results with your doctor.

What does the result mean?

High HDL cholesterol is better than low HDL cholesterol. A healthy HDL cholesterol level is over 1 mmol/L.

However, your HDL cholesterol should be interpreted in the context of the overall findings from the lipid profile and in consultation with your doctor about other risk factors for heart disease.

Is there anything I should know?

HDL cholesterol should not be measured when a person is unwell. Cholesterol is temporarily low during acute illness, immediately following a heart attack, or during stress (like from surgery or an accident). You should wait about 6 weeks after any illness to have cholesterol measured.

In women, HDL cholesterol may change during pregnancy. You should wait about six weeks after your baby is born to have your HDL cholesterol measured.

Common questions

What treatments are recommended for low HDL cholesterol levels?

If you have low HDL cholesterol you may be able to increase it by making some changes in your lifestyle. If you are a smoker, stopping smoking may increase your HDL cholesterol. Exercising more and, if you are overweight, losing weight may also help. A diet with a moderate intake of carbohydrates and fat helps maintain healthy HDL cholesterol levels. The type of fat you eat is also important, particularly avoiding `trans' fatty acids, such as the modified vegetable fats that may be present in deep fried `fast-foods'. Moderate alcohol consumption may increase HDL cholesterol. Taking fish oil supplements and Vitamin B3 supplements may also increase HDL cholesterol and your doctor may prescribe medication to help.