Understanding the Meaning of Laboratory Tests

Participants in Healing Heart support groups are requested to have some laboratory tests done as they begin the program and then repeat these tests at the end of the ten week program. They can decide on the basis of changes in test results and the way they feel whether the lifestyle changes were worth the effort. Almost all have chosen to keep the changes, rather than return to their former lifestyle and problems. You are encouraged to do the same, getting your lipids, blood pressure, weight and body fat measured at the start and again at the end of ten weeks. Seeing the numbers change for the better is proof that the program is working for you. But what do those numbers mean? The following is a limited, brief explanation to help give you basic understanding of the the meaning and normal values of these tests. For more information, ask your physician for an interpretation of your test results.

The cholesterol level in your blood is a highly useful indicator in your health profile. It is measured in the U.S. in milligrams per deciliter (mg/dl) (see box below). The typical level of total serum cholesterol (the amount most commonly found in Americans) is somewhere between 130 and 350 mg/dl., with the average around 215. To reduce plaque and heart attack risk, you should keep your cholesterol under 150. Cholesterol levels provide information about many risks. If your cholesterol level is near the 215 average mark, your lifetime risk of heart disease and stroke is greater than 50%, of gallbladder disease 40% (90% of gallstones are made out of cholesterol), of breast cancer in women 10% and of colon cancer 5%. Even small changes can have huge effects. Lowering the cholesterol level from 260 to 200 decreases the risk of dying from heart disease by 500%.

On November 12, 2013, The American Heart Association and the American College of Cardiology published modifications to their guidelanes on cholesterol. This link will take you to that announcement. While they have lowered thair recopmmendations, they are, in our opinion, still much too high. We continue to recommend that all necessary actions be taken to keep total cholesterol under 150 mg/dL.

If your numbers are much different - somewhere between one and ten...
it means that your lipids are measured in millimoles per liter (mm/l) as it is in most places outside of the US. You can multiply mm/l by 38.61 to get the equivalent in mg/dl (or multiply mg/dl by 0.0259 to get mm/l), or click here for cholesterol conversion.

In addition to total serum (blood) cholesterol, there are three lipoproteins which also give useful information. HDL (High Density Lipoprotein) is often called good cholesterol. The typical range in Americans is between 29 and 77. Any measure above 55 mg/dl is considered acceptable, but levels closer to 100 are related to a lower chance of coronary artery disease. In the process of lowering total cholesterol, HDL may also come down for a while. A Heart Risk Ratio is calculated by dividing total cholesterol by HDL. As total cholesterol is lowered, HDL will also often decline, sometimes causing the ratio to rise. This is not always a cause for serious concern, as the ratio has less significance as the total cholesterol level gets closer to 150. See the section on Risk Factors for an interpretation of the ratio.

LDL cholesterol, which is often called bad cholesterol, is useful in assessing heart disease risk, but many physicians feel it is not nearly as important as the total cholesterol and HDL counts. The typical level in the U.S. is between 75 and 185. It is considered beneficial to keep LDL levels under 130, as higher levels are associated with greater risk.

Some labs also calculate VLDL, very low density lipoproteins. The typical range is from zero to 40 mg/dl. The link between VLDL and heart disease risk is less well established.

There is some controversy about tests to detect the level of C-reactive protein (CRT) and its value in predicting heart disease. On November 14, 2002, 2001 the New England Journal of Medicine published the results of one of the most definitive studies on this subject. To read a summary of that study, posted on the Healing Heart Discussion Group, click here.

Body Fat Percent is a way to determine the proportion of fat to other tissue. When fats are reduced and exercise increased, sometimes weight doesn't drop as expected. The fatty tissue may be replaced with newly formed muscle cells, which weigh more than fat. It is helpful to know the percent of fat in the body is being reduced, even if weight sometimes doesn't change as much as expected. To see general guide to body fat percentage, click here.

Triglycerides are the amounts of fats in your bloodstream. Since triglycerides usually go up after eating, a test for triglycerides should be taken only following 14 hours of fasting, eating no foods and drinking nothing but water. The typical triglyceride level is between 35 and 219 mg/dl, and levels below 100 are considered helpful in reducing heart disease risks. Triglyceride levels are somewhat different for men and women, and also change with age, rising to nearly double the value of age 6 by age 60, and then they slowly decline. Triglyceride levels commonly go up for three to six months when on a low fat, vegetarian diet. They usually go below the starting level for much improvement after that. Fats in the blood rise to the top like the fats in soups or gravies do after they cool. If people who eat the typcially high fat standard American diet could see their blood sample after 8 hours, with its layer of yellow-white fat floating above the red and sticking to the sides of the glass tube, it would be easier to motivate them to eat more sensibly.

Triglycerides, like cholesterol, is measured in mg/dl in the USA and in mm/l in most of the rest of the world, but the conversion factor for triglycerides is different from the one for cholesterol. For a triglycerides conversion chart, click here.

Blood Pressure is measured in two numbers. The higher number, called systolic, shows the highest amount of pressure on the walls of blood vessels during each beat of the heart. The lower number, diastolic, shows the amount of pressure on the arteries when the heart is resting between beats.

Various things can temporarily affect blood pressure, so it is usually best to take an average of many measurements rather than use only one. When some people go to a clinic their anxiety can cause blood pressure to be much higher than normal, a condition called white-coat hypertension . Recent use of coffee or tobacco can raise blood pressure. Many medications can raise or lower blood pressure.

Age, health problems and physical fitness are considerations in deciding if a person's blood pressure is normal. A general guide is given here, but you should check with your physician to decide if yours is safe or requires attention.

The following two tables show what is generally considered normal and high levels of blood pressure. Many different health conditions and medications may affect what is normal for each person.

Level Hg/mm Signifigance Usual Recommendation
85 & below normal check @ 2 years
85 - 89 high-normal check annually
90 - 104 mild hypertension check 2 months later
105 - 114 moderate hypertension medical intervention
115 & above severe hypertension therapy may be advised

When diastolic pressure is normal, a condition called isolated systolic hypertension may occur if systolic measures are abnormally high. This is more common in older persons.

Isolated Systolic Hypertension (when diastolic is under 90)
Level Hg/mm Signifigance Usual Recommendation
140 & below normal check @ 2 years
140 - 159 borderline check 2 months later
160 - 199 hypertension consult your physician
200 & above acute hypertension therapy may be advised

New research indicates that the top number in a blood pressure reading is more useful than the bottom number in determining heart disease risk. Doctors have typically looked at diastolic pressure (the bottom number) to assess whether people are at risk for heart disease, but a study published in the Archives of Internal Medicine in early 2002 adds to growing evidence that it's systolic blood pressure (the top number) that matters most.

In the study, researchers looked at 4,714 French men, whose average age was 52, for a period of 14 years. They found that during that period, men with systolic blood pressure of 160 or higher had more than twice the risk of death from heart disease compared to men with systolic blood pressure of less than 140. Systolic pressures between 140 and 160 were associated with a slightly increased risk. The diastolic pressure reading did not appear to have anyeffect on heart disease risk. Although earlier studies suggested that high systolic blood pressure was an important risk factor for elderly people, the new study shows that it is also important in middle-aged people. The researchers concluded that the optimal blood pressure reading is 120 over 80 or lower.

Here's a rundown of some more common tests to determine if one has heart disease, what kind, and how serious, from simple to high-tech, which may be advised under different circumstances.

Electrocardiogram (ECG or EKG). This fast, painless testrecords the heart's electrical activity through small electrodes placed on your body. It is not usually part of the routine physical xam for healthy people, but may be done if you have symptomsor certain risk factors. It can detect a heart attack (past or present) r be used to diagnose specific problems, including irregular heart rhythms or enlarged heart chambers. A Holter Monitor allows for continuous ECG monitoring, via a small recorder and electrodes that you wear under your clothing for 24 hours (or longer). An event monitor, typically worn for several weeks, records heart activity only when you feel symptoms and push a button.

Exercise stress test. This is an ECG taken while you use a treadmill or stationary bike. It shows how much stress your heart can tolerate before problems develop, such as abnormal blood pressure or irregular heart rhythm, and can determine what a safe level of exercise is for you. Because you are exerting yourself, the effects of coronary blockage are more likely to show up here than in a regular ECG. Stress tests carry a slight risk and must be closely monitored by a physician or technician. Results may be less accurate in women.

Echocardiogram. A device (transducer) beams ultrasound waves at your heart, and the returning echoes are used to create a picture of the heart and its moving valves. If a "color Doppler" is used, blood flow through the heart can be evaluated. There are several kinds of echocardiograms, including a stress echocardiogram, done immediately after a treadmill workout, which can reveal abnormal heart contractions.

Myocardial perfusion. This nuclear imaging test evaluates blood flow to the heart. A small amount of radioactive material is injected in a vein, and then a special camera captures images as the substance passes through your heart and arteries. The test usually consists of two parts: one at rest and one after exercise (or a drug may be given that has a similar effect on the heart as exercise), and the images compared. In a heart free of blockages, there should be little difference at rest and after exercise.

Electron-Beam Computed Tomography (EBCT). This imaging procedure detects calciu deposits in coronary arteries, which may signal the presence of CAD. Studies have found that the higher the calcium, the higher the risk for heart attacks. But the use of EBCT is still being debated because it's unclear how much information it provides for predicting heart disease beyond an evaluation of standard risk factors. And it may expose many people to needless radiation, though the dose is low.

Computed tomography angiography (CTA). Also referred to as rnultidetector scanning, this rapidly developing imaging technology produces high-resolution, three-dimensional computerized pictures of the moving heart and large blood vessels, which reveal the extent and nature of plaque formation or calcium deposits. Contrast material may be injected in a vein to improve the quality of the images. Newer systems produce better images much faster-and with less radiation.

Coronary magnetic resonance imaging (MRI) or magnetic resonance angiography (MRA).This test uses magnetic fields and computers to produce images of the heart and arteries. It can detect valve problems, heart enlargement, and vessel disease, as well as damaged heart tissue and other abnormalities. Contrast material may be injected. An advantage is that it detects CAD without radiation and is not invasive. Though relatively new and expensive, it may turn out to be the preferred way to visualize the coronary arteries, and may one day be useful in diagnosing people who come to the emergency room with chest pain.

Coronary angiogram. This procedure involves inserting a catheter into a vein, which is then guided to the heart. Contrast material is injected to visualize the heart on X-rays and observe the heart, arteries, and valves at work. Angiography is the gold standard for diagnosing CAD,but because it isinvasive and involves some risks, it is done primarily in people who are candidates for coronary bypass surgery or angioplasty.

Testing you probably don't need: Some clinics offer EBCT, full-body CT scans, and ultrasound tests without a doctor's referral. There's no evidence these tests are worthwhile for people at low risk of heart disease-which is why most insurance won't cover them in people who have no symptoms or other significant risk factors. Moreover, tests that use X-rays, particularly fullbody CT scans, can expose you to high levels of radiation, especially when done repeatedly. All diagnostic tests produce false positive results (indicating disease when none is present), but more so in low-risk people. Such a result would lead to further unnecessary and costly procedures, as well as additional worry.

Revised 8-10-2008

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©1994, 1996, 2002
Dr. Neal Pinckney
Healing Heart Foundation