GOOD & BAD CHOLESTEROL: PART 2
Explaining cholesterol ratios & fasting or non-fasting blood tests
IN the previous article Good & Bad Cholesterol: Part 1, factors such as total cholesterol, HDLcholesterol, LDL-cholesterol and triglycerides were discussed. In recent years, another component of the lipid profile has been added, called the NonHDL cholesterol. This is a useful figure and measures ALL the cholesterol in the circulation that is NOT the good HDL. The non-HDL cholesterol has been shown to be a useful predictor of risk.
THE RATIO OF LIPID COMPONENTS.
The ratio of these individual components is also important. The ratio is a comparison or balance of how much HDL or good cholesterol there is, compared to total cholesterol. A low ratio, less than 4 is generally ideal. For example;
• If the total cholesterol is 4mmol/l & HDL-cholesterol is 1 mmol/l, then the ratio is 4.
• If the total cholesterol is 6 mmol/l, but HDL-cholesterol is 2, then the ratio is 3. The ratio of 3 is ‘better’, then a ratio of 4. Thus, even with a higher total cholesterol, the ratio is more favorable when HDL is also higher. These simple numbers as a ratio, gives some idea in terms of a starting point for risk calculation. This information can give an estimate of your risk of an event.
TARGET CHOLESTEROL IN PRIMARY PREVENTION.
One of the reasons to measure cholesterol is to have ‘targets for cholesterol’. In primary prevention i.e. preventing people having their first coronary event, the current guidelines in Australia recommend that we need to aim for LDL-cholesterol level of 2mmols per litre or less.
TARGET CHOLESTEROL IN SECONDARY PREVENTION.
In secondary prevention, i.e. a patient who has had an event, we want to reduce the risk of that person having another event. We want to be very proactive in our management strategies for those people. We aim at a ‘target’ LDL-cholesterol of less than 1.8mmols per litre. Those guideline recommendations will come down as some of our newer trials start to be incorporated into the evidence base that informs guidelines. These most recent trials are showing that even for secondary prevention patients who are already well treated with lipid lowering drugs, have demonstrated even better outcomes if LDL-cholesterol is lowered even more, i.e. in high-risk individuals to below 1mmol per litre. There appears to be no further adverse side effects demonstrated, only a reduction in the risk of heart attack.
FASTING OR NON-FASTING BLOOD TEST.
Should cholesterol measurements be made on fasting or non-fasting blood test? Mostly the LDL and HDLcholesterol are not greatly different in the fasting and non-fasting states, though the triglycerides will be significantly elevated after food, as you might expect, since they are involved in the transport of fats. Non-fasting lipid profiles provide
convenience and may even be done at time of a clinic visit. A fasting blood test is more useful because a simultaneous fasting blood glucose can be measured to determine a fasting glucose and insulin level. Fasting glucose and insulin levels provide an indication of prediabetes or a diabetic condition. As always, never forget things like blood pressure and lifestyle, because they’re really important. Even though we have looked at the values in cholesterol tests, it is also very important to check your fasting glucose and insulin levels. I hope you’ve found these articles in
Great Health GuideTM informative and that they have answered some questions on cholesterol testing for you. If you have any feedback or questions, don’t hesitate to let us know.
Dr Warrick Bishop is a cardiologist with special interest in cardiovascular disease prevention incorporating imaging, lipids and lifestyle. He is author of the book ‘Have You Planned Your Heart Attack?’, written for patients and doctors about how to live intentionally to reduce cardiovascular risk and save lives! Dr Bishop can be contacted via his website.