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Cholesterol

Updated 02 October 2018

Diagnosing high cholesterol

It's essential to know whether or not you have raised cholesterol levels and, if so, to what extent.

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There are many risk factors that influence the vascular disease process. The complications can be quite dramatic: angina, heart attacks, strokes or even gangrene. 

One should also bear in mind that the final cholesterol concentration is the outcome of hereditary factors, lifestyle factors and other diseases that may be present.

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 (hypercholesterolaemia) 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.

Associated conditions

Conditions that may result from high 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. The short interruption of brain function is due to small particles of clot and/or cholesterol breaking off from the artery and not interrupting blood flow sufficiently to permanently damage the brain. When this happens it is called a 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 cornea of the eye. Most commonly, cholesterol accumulates in the Achilles tendon and sometimes the tendons of the hands but this takes a few decades and is not always the case.
  • 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 the 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.

The total cholesterol does not accurately reflect the risk because higher LDL cholesterol increases risk and lower HDL cholesterol increases the risk. 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 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. Originally the studies of risk and measurement of LDL cholesterol were done in the fasted state as especially triglycerides change after a meal. Nowadays the LDL cholesterol is measured directly and it appears that a non-fasted state may give a better indication of risk.

This is because less removal of dietary fats exposes the arteries more to fat infiltration. 

People who could benefit from cholesterol tests:

  • 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 diabetes, early heart disease in the family, and family members with total cholesterol more than 7mmol/L)

A single test in adulthood may suffice but if there’s significant risk or conditions change, testing should be more frequent. More frequent testing is also required to monitor the control of the blood cholesterol of those already on treatment for HC. Those with severe derangements in cholesterol and/or triglyceride may need additional testing for specific lipid disorders.

Guidelines for treatment 

The values obtained from a blood test are used as guidelines for treatment, and follow-up testing is used to monitor progress. The final decision about introducing medication is the risk of heart disease in the future.

This is very high in persons who already had a vascular event and those who have an inherited condition, but in diabetic persons there is also such an increase in risk that medication is prescribed to attain ideal levels of LDL. 

Apart from LDL and HDL cholesterol, the triglyceride concentration and Lp(a) concentrations are important considerations for risk. 

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 in high risk settings.

  • Lp(a) is a modified form of LDL and is 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).

There is evidence that raised homocysteine levels are implicated in recurrent venous thrombosis, but there is no agreement among experts that homocysteine causes 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.

However, very high homocysteine levels can result in strokes in young persons or even in children. This condition can be suspected when there are problems with the lenses of the eyes in children.  

Reviewed by Prof David Marais, FCP(SA), Head of Lipidology at Groote Schuur Hospital and the University of Cape Town, January 2018

Image credit: iStock

 

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