PRL: Physicians Reference Laboratory

PHYSICIANS REFERENCE LABORATORY

CLA: CARDIAC RISK

HEART DISEASE

Confused about all of the information in the media concerning your heart, blood vessels and risk of having a heart attack? You are in good company! There are two fundamental reasons for much of the confusion: (1), the subject is complex and (2), nobody yet has all or even most of the answers. Let’s take a look at what we do know and then we may be able to decide what next to do.

WHAT WE KNOW:

We’ve known for a long while that there are associations between abnormal amounts of certain chemicals in our blood and having heart attacks, strokes, and high blood pressure. The chemicals we are talking about are cholesterol (C), triglycerides (T) and certain lipoproteins (“lipo” refers to fat). The lipoproteins are attached to C and/or T and transport them in the blood. These proteins, for our purposes, are lumped into categories according to their densities (how “thick” they are): (1) high-density lipoproteins (HDLs), (2), low-density lipoproteins (LDLs), (both being bound to cholesterol), and (3), very low-density lipoproteins, which are more associated with triglycerides. These chemicals are necessary for life, but also, when there is too much C, T, and associated lipoproteins in the blood, they appear to play roles in causing calcified lumps or plaques in our arteries’ walls (called atheromas or “hardening of the arteries”). We know that high levels of these chemicals in a person’s blood are associated with an increased incidence of heart attack, stroke and high blood pressure. People with large amounts of HDLs seem to have fewer of these conditions. We also know that some groups of people are at an increased risk for heart and blood vessel disease: males, menopausal women, the aged, smokers, diabetics, over-eaters and fatty diets, certain families (genes), those who are chronically stressed, don’t exercise, have high blood pressure, are overweight, who have abnormal chemical tests as below, to name a few.

WHAT CAN WE DO?

If we are in one or more of the above high-risk groups, we need to make a serious effort to change what we can. Secondly, we can find out how our bodies are doing right now, so that we have a baseline from which to measure our progress. Though information from the individual tests for measuring the chemical mentioned above are each helpful, they are best considered together, to give the most reliable “snapshot” of what’s happening in our blood vessels at that moment. Consequently, we recommend measuring all of them at one time (a “profile”), after an overnight fast of at least 12-14 hours. The fast is very important because, without it, most of the test results will be artificially high and nearly useless.

A short word about lab tests in general: Before laboratory tests are used for clinical purposes, they are first evaluated in use on a very large group of healthy human beings. The results of these tests are then statistically evaluated and used to develop what is called a “reference range”. This range indicates the range in which most healthy people’s test results fall. Below are listed the PRL reference ranges of the above tests. Please note also that, with these particular tests, the “reference ranges” do vary with age, so your age (and sex) should be considered along with the test results.

UNDERSTANDING YOUR TEST RESULTS:

Following are some general definitions that may help you understand your test results:

TEST	REFERENCE RANGE	COMMENTS / CLINICAL SIGNIFICANCE
Cholesterol (total or CT)	100-200 mg/dL	#1
Triglycerides	20-200 mg/dL	#2
HDL Cholesterol (HDL-C)	30-80 mg/dL	#3
LDL Cholesterol	50-140 mg/dL	#4
VLDL Cholesterol	less than 40 mg/dL	#5
TC/HDL-C Ratio	less than 4.5	#6

#1 Cholesterol or TC is the total amount of cholesterol that has been measured in your blood at that particular time. It is present in a number of different chemical sources and the amount present varies from moment to moment. Some of it comes from your diet and some is made in your liver. Cholesterol is essential for life but, in excess, builds up in blood vessel walls and does considerable damage. In general, up to 200 mg/dL is considered normal in our population, between 201-239 mg/dL is considered borderline abnormal, and 240 mg/dL and above are considered abnormal.

#2 Triglycerides are the main way that your blood transports fat, for storage and also for your tissue cells to burn, giving you energy. After you eat and digestion has occurred, large amounts of triglycerides are released into your blood. Your liver also makes triglycerides from extra carbohydrates and other calorie-containing chemicals.

#3 HDL-Cholesterol (“good cholesterol) is that portion of the total blood cholesterol that is attached to the high-density lipoproteins. If it is present in larger quantities, it is believed to be involved in keeping cholesterol from being deposited in the blood vessel walls and may also assist in removing cholesterol from them.

#4 LDL-Cholesterol (“bad cholesterol”) is that fraction of the total cholesterol that is bound to low-density lipoproteins. When it is elevated in the blood, it is associated with fatty build up in the blood vessel walls, causing them to narrow, become rigid and possibly clogged.

#5 VLDL is one of the lipoproteins particularly associated with triglycerides in certain types of blood vessel disease.

#6 Researchers have found that the arithmetic ratio of TC (total cholesterol) to HDL-Cholesterol has good predictability regarding risk of having heart disease. It is desirable to have a TC/HDL-C ratio of less than 4.5/1.

If the results from your tests are not within their respective reference ranges, you should make an appointment with a physician to further evaluate and investigate the results. If you would like to discuss the meaning of your test results, our clinical pathologist will be glad to chat with you.

Thanks for coming in and using Physicians Reference Laboratory’s Community Laboratory Access option to assist you in taking charge of your health care.

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