Updated 01 October 2014

Diagnosing high cholesterol

Do I have raised cholesterol levels or not?

Before discussing how to treat the condition and handle the risk factors, it is essential to know whether or not you have raised cholesterol levels and, if so, to what extent, and what type of high cholesterol (hypercholersterolaemia) you have.

1. Symptoms

The most common symptom of high cholesterol is no symptoms at all. The vast majority of people with high cholesterol are therefore unaware of their condition until they suffer a heart attack, stroke or gangrene. Although high cholesterol (HC) itself rarely causes symptoms, its complications can be devastating.

High cholesterol may be detected during a routine blood test that measures cholesterol levels.

Conditions that may result from cholesterol (such as coronary artery disease [CAD] and stroke) may be the first clue that you have high cholesterol.

The first symptom of CAD is often angina (chest pain). Angina usually occurs during activities that raise the heart rate, such as walking uphill. However, many people suffer from CAD for several years without having any symptoms.

Unless you have a transient ischaemic attack (temporary interference with blood supply to the brain), it is rare to have any warning signs of an oncoming stroke.

In people with several of the genetic causes of high cholesterol, other distinct features may be present and helpful in making a diagnosis. In people with familial hypercholesterolaemia (FH), deposits of cholesterol may collect in tendons, skin or eye tissue. Most commonly, cholesterol accumulates in the Achilles tendon and sometimes the tendons of the hands.

Yellowish deposits of cholesterol in the eyelids, termed xanthelasma, are also sometimes seen with moderate elevations of cholesterol. However, a white line or arc on the cornea of the eye is more specific to severe inherited disorders in young adults.

2. Measuring blood levels

There is only one way to find out if your blood lipids are within normal range: you must have them measured. It is important to know not only what your total cholesterol value is, but also how that value is made up. That’s because while the total reading is important, the readings of subtypes such as LDL and HDL cholesterol are also important, because each type has its own influence on your overall risk profile.

You can have your cholesterol checked via full screening or finger-prick tests, as offered at some pharmacies.

However, there is only one test sufficiently accurate and reliable for diagnosis and treatment plans: the fasting full lipogram. This is a blood test performed by a pathologist that provides accurate measurements of your total cholesterol, as well as the levels of LDL, HDL and triglycerides. Based on these readings, the laboratory also computes your risk ratio for cardiovascular disease.

Several issues are of importance here:

1.    You must fast for at least six hours (preferably overnight) before the blood sample is
       taken. The blood sample measures the circulating total cholesterol (TC) and other lipids
       (fats) such as triglycerides and lipoproteins present in your blood at that time. If the
       blood is taken too soon after a meal, the test will measure your own levels as well as
       the fat content of the meal just eaten. It therefore gives little indication of how the body
       handles fats and cholesterol. This "baseline" condition is especially important when LDL
       cholesterol is calculated and not directly measured.

2.    While the TC value is important, it is more meaningful to know your LDL and HDL     
       cholesterol. The TC value may be "normal", but if the reading is composed almost entirely
       of LDL, and not enough protective HDL, then you are at higher risk for heart attack
       and/or stroke than what your TC suggests. If you are under the impression that the
       reading is normal, you may not receive the treatment necessary to prevent a disaster.

3.    There are international standards of what is regarded as a normal reading and a high    
       reading requiring action.

4.    Interventions such as lifestyle changes and/or medication will not only be based on   
       blood readings. For example, if you have a strong family history of heart disease or
       another risk factor such as hypertension or diabetes, you’ll be a candidate for early
       intervention at a TC level below that of someone who does not have other risk factors.

5.    Measurement of Lp(a) and homocysteine may be relevant (see below).

Who and when to test

Most experts agree that everyone older than twenty years and without risk factors should have cholesterol tests at least once and then probably every five years.

People who could benefit from cholesterol tests at least once a year include:

•    Men over the age of 35 years
•    Women over the age of 45, or who are menopausal
•    Anyone – including children – with risk factors for heart disease (e.g. hypertension or  

More frequent testing may be required to monitor the progress of those already on treatment for HC. Those with familial hypercholesterolaemia may need additional testing for specific lipid disorders.

Know the numbers

Here are values accepted as normal or ideal:

•    Total cholesterol: lower than 5 mmol/L
•    LDL: lower than 3 mmol/L when there is no manifest arterial disease and lower than 2.5
      mmol/L when arterial disease is present
•    HDL: higher than 1 mmol/L
•    Triglycerides: lower than 1.7 mmol/L
•    Risk ratio (TC/HDL): higher than 4 constitutes moderate risk, higher than 5 constitutes          high risk

The values obtained from a blood test are used as guidelines for treatment, and follow-up testing is used to monitor progress.

If you have known risk factors such as diabetes, or a normal TC but very high Lp(a) levels (see below), then treatment would be considered despite a normal TC. You would also probably start receiving treatment even if your TC is lower than normal, just to make sure the risk of cardiovascular complications is reduced.

Lp(a) is a modified form of LDL and is considered a genetically determined marker for a high risk of cardiovascular disease (CVD) – the higher the blood level, the greater the risk – and therefore an indication for early treatment. While treating raised TC will not lower levels of Lp(a), it will lower your overall risk of CVD.

Lp(a) levels by themselves are not good predictors of CVD risk, but there is a strong association if raised Lp(a) occurs together with raised TC, and even more so if the HDL (the protective cholesterol) is too low. The blood levels of what is considered normal also vary widely according to population groups. Diet has little effect on Lp(a).

Homocysteine is an amino acid present in all of us: normal values are 5-15 µmol/L. Excessively high levels are found in a rare genetic disorder, but moderately raised levels are present in up to 7% of the population of the USA. Raised levels are associated with:

•    Cigarette smoking
•    Chronic kidney failure
•    Deficiency of vitamin B12 or folic acid
•    An occasional side effect of fibrates or nicotinic acid used in the treatment of 

There is evidence that raised homocysteine levels are implicated in recurrent venous thrombosis, but there is no agreement among experts that homocysteine helps cause CVD. In several large studies, treatment which lowered homocysteine levels made no difference to the incidence of CVD events (e.g. heart attack or stroke) or to the number of CVD deaths.

Read more
Causes of high cholesterol
Treating high cholesterol
Knowing cholesterol better

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