At a glance

Also known as

LDL; LDL-C; 'bad' cholesterol

Why get tested?

To determine your risk of developing cardiovascular diseases such as heart attack and stroke

When to get tested?

Screening 

  • As part of a health examination with a lipid profile; every five years from age 45 (35 for those of Aboriginal and Torres Strait Islander background) in adults with no risk factors for heart disease
  • More frequent screening may be indicated for those considered moderate-to-high risk of cardiovascular disease. 

Monitoring  

  • Patients on lipid-lowering therapy require regular monitoring of LDL cholesterol (as part of a lipid profile) to assess their response to treatment.  The frequency of tests for monitoring purposes will be specified by your doctor
Sample required?

A blood sample drawn from a vein in the arm (most commonly) or ocassionally from a fingerprick (capillary).
Measurement of LDL cholesterol generally requires an 8-12 hour fast before the sample is taken. Only water is permitted. Fasting may not be required in all circumstances.  You should follow the instruction of your doctor.

What is being tested?

Low-density lipoprotein (LDL) is a type of lipoprotein that carries cholesterol in the blood. The test for LDL cholesterol (LDL-C) measures the amount of cholesterol bound to LDL in the blood. LDL cholesterol is considered to be undesirable because it deposits excess cholesterol in the walls of blood vessels and contributes to 'narrowing of the arteries' (atherosclerosis) which may lead to conditions such as angina, heart attack and strokes. Hence LDL cholesterol is often termed 'bad' cholesterol. The test for LDL cholesterol measures the amount of cholesterol bound to LDL in blood. 

LDL-C is usually not measured directly, but calculated by an equation which uses the other components of the lipid profile. Occasionally LDL-C can be measured directly. This test is known as direct LDL and is described separately.

How is the sample collected for testing?

The test for LDL cholesterol uses a blood sample. Most often, the blood sample is collected by venipuncture (using a needle to collect blood from a vein in the arm). Occasionally a fingerprick test can be used. LDL-C is never measured on its own, but is included in a group of tests known as a lipid profile.

Measurement of LDL cholesterol generally requires an 8-12 hour fast before the sample is taken. Recent evidence suggests that a non-fasting lipid profile may be acceptable, however this is yet to be endorsed by governing bodies in Australia.  Unless told otherwise, you should fast for 8-12 hours before the sample is collected.  Only water is permitted during the fast.

The Test

How is it used?

The test for LDL cholesterol is used to predict your risk of developing cardiovascular diseases such as coronary heart disease and stroke. LDL cholesterol is part of the cardiovascular risk assessment. Results of the LDL cholesterol test and other components of the lipid profile are considered along with other risk factors to assess an individual’s risk of developing cardiovascular disease in the next 5 or 10 years. Decisions can then be made about whether treatment is required to lower this risk.  

Treatment options may include lifestyle changes such as diet or exercise programs or lipid-lowering drugs such as statins. The treatment target for LDL cholesterol is usually <2.0 mmol/L. although your doctor may decide that a different target is more appropriate for you.

Once a patient has been diagnosed with high LDL cholesterol and has been started on treatment, it will be measured more frequently to assess the response to treatment

When is it requested?

LDL cholesterol levels are ordered as part a lipid profile, along with total cholesterol, HDL cholesterol (HDL-C), and triglycerides. This profile may be used as a screening test in a healthy person as part of a routine health check, for Aboriginal and Torres Strait Islander adults aged 35 years and over and otherwise adults aged 45 years and over. If the individual is considered to be low risk, the LDL-C should be remeasured in 5 years.  Individuals at moderate or high risk require more frequent retesting.

A lipid profile may be requested on someone who has had a high total cholesterol to see if the total cholesterol is elevated because of too much LDL-C. A lipid profile may also be requested in individuals who have one or more major risk factors for cardiovascular disease regardless of their age.

LDL-C may also be requested at regular intervals to evaluate the success of lipid-lowering lifestyle changes such as diet and exercise or to determine the effectiveness of cholesterol-lowering drugs such as statins

LDL-C may be falsely decreased if you are acutely unwell at the time of measurement (for example, if you have an infectious disease, if you are recovering from a heart attack or have recently had surgery).  A lipid profile should be measured once you have recovered from this illness.
 

Reading your results

Lipid Profile – cholesterol (total, HDL and LDL) & triglycerides
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.
 
It is important to realise that the format and look of reports often differ between laboratories so your results form may not look exactly like this.
 
  *Requesting Doctor   *Patient    
Name: Michael Smith   Paul Harding    
Address: Rodwell Medical Centre, 12 Main Street, Rodwell NSW   58 Bramble Street, Rodwell NSW    
Date of birth:     12-Nov-1990    
Sex:     Male    
           
*Date of report: 28-Feb-19 16-Mar-19
      Latest results *Reference Interval *Units
*Collection date: 28-Feb-19 16-Mar-19    
*Collection Time: 8:30 9:00    
*Request No: 123456 345678    
Test names          
Biochemistry
Cholesterol 9.0 H 9.1 H ≤5.2 mmol/L
Triglycerides 1.2 1.5 ≤ 2.5 mmol/L
HDL Cholesterol 1.1 1.2 1.00-2.50 mmol/L
LDL Cholesterol 7.4 H 7.2 H ≤ 3.5 mmol/L
Comment: LDL-Cholesterol ≥ 6.4 mmol/L:
Familial hypercholesterolaemia, an autosomal dominant cause of premature cardiovascular disease is highly likely (risk greater than I in 2).
Recommend http://www.athero.org.au/calculator to calculate diagnostic score and http://www. athero.org.au/fh/health-professionals/what-is-familial-hypercholesterolaemia-fh/ to assist with diagnosis and management, if required.

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 test result mean?

A high LDL-C is associated with an increased risk of cardiovascular disease.  Because LDL-C is only one component of the cardiovascular risk assessment (which takes into account many other factors such as smoking status, family history and blood pressure), the LDL-C result which is considered “high” will vary from person to person.  However, in general, an LDL cholesterol above 3.0mmol/L is associated with a potentially increased risk.

If you are on treatment, it is common to aim for an LDL-C below 2.0mmol/L, however your doctor may pick a more appropriate treatment target based on your own individual circumstances.  It is important to remember that any reduction in LDL cholesterol reduces cardiovascular risk, even if you do not meet your treatment target.

Those with LDL-C above 5.0mmol/L [ST1] should be reviewed with regards to whether they may have familial hypercholesterolaemia (see below). 

If your lipid levels are mildly abnormal, a second confirmatory sample may be taken on a separate occasion before a definitive diagnosis is made as the amount of cholesterol in the blood does vary a little from day-to-day. 

About Reference Intervals

Is there anything else I should know?

Measurement of LDL-C generally requires an 8 - 12 hour fast — meaning that you must not eat or drink anything that has calories for 12 hours before your blood is drawn. You may drink water. This is because LDL-C is usually calculated from the results of other tests, including triglycerides, that require fasting. This result may be reported as 'calculated LDL-C'. Some laboratories can measure LDL-C directly using a special technology and fasting is not necessary. This test is usually called 'direct LDL-C'.

LDL cholesterol should be measured when a person is healthy. LDL cholesterol is temporarily low during acute illness, immediately following a heart attack, or during stress (like from surgery or an accident). You should wait at least six weeks after any illness to have LDL cholesterol measured.

In women, cholesterol is high during pregnancy. Women should wait at least six weeks after the baby is born to have LDL cholesterol measured.

Familial hypercholesterolaemia (FH) is a severe form of elevated cholesterol levels that runs in families. It is often undetected until damage is done and the person develops cardiovascular disease. It can be easily screened for and treated early in life. Information about FH can be found at the FH Australia network site. Individual risk of having FH can be determined using this online calculator or using this form.
 

Common Questions

What treatments are recommended for high LDL cholesterol levels?

The first step in treating high LDL-C is adoption of lifestyle changes, including decreasing the amount of saturated fat in the diet, achieving and maintaining desirable body weight, and getting regular exercise.  If lifestyle changes do not adequately lower LDL-C, drugs such as statins may be prescribed. For people with certain combinations of risk factors and LDL-C levels, drug therapy may be prescribed in concert with lifestyle changes.
 

How much will LDL cholesterol change as a result of lifestyle changes, like exercise or diet?

Adoption of a diet low in saturated fat (less than 6% of calories from saturated fat) will usually lower LDL cholesterol by about 10%.

Should someone with a family history of high LDL cholesterol levels be tested at a young age?

Children who have a family history of very high LDL cholesterol or premature cardiovascular disease (generally considered to be a first-degree relative with heart attack or stroke before age 55 if male, or 60 if female) should have a lipid profile once they reach 5 years of age.  This is because these patients may have an inherited condition such as familial hypercholesterolaemia (see below) which will benefit from early treatment.


Last Review Date: September 30, 2020


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