LABORATORY EVALUATION AND SCREENING

CHOLESTEROL AND LIPOPROTEINS: Cholesterol is one of the fatty components of our blood. Its importance is that it is used to form cell membranes and some hormones. An elevated level of cholesterol has been shown to be a major risk factor for the development of atherosclerosis. In order for cholesterol to be used, and, more importantly, metabolized, it must be transported in the blood to the cells by chemicals which are specialized carriers of both lipids and proteins, which are called lipoproteins. There are two types of lipoproteins called Low-Density Lipoprotein, or LDL, and High-Density Lipoprotein, or HDL.

LDL:

LDL is the primary lipoprotein that transports cholesterol. An elevated level of LDL is known to increase the risk of atherosclerosis by depositing within the wall of an artery in the process of forming a plaque. As mentioned, this reduces the amount of blood flowing through the artery and can result in tissue damage leading to a heart attack or stroke. This is why you will hear LDL referred to as bad cholesterol.

HDL:

HDL is less prevalent than LDL, but its importance is in its ability to carry cholesterol away from the arteries and to the liver where it is metabolized and eliminated from the body. As such, the less HDL that is available, the less cholesterol is removed from arteries and eliminated, and more is available to deposit in arterial walls.

TRIGLYCERIDES:

Triglycerides are the form in which most fats exist in food and in the body. Cholesterol and triglycerides together comprise the lipids (fats) present in the plasma (blood stream). While cholesterol is used as a component of cell walls and in the production of certain hormones, triglycerides are primarily used as sources of metabolic energy (calories).

Triglycerides in the blood come from two sources. One, they are present in the foods we eat. Two, other foods, such as carbohydrates, which also serve as sources of metabolic energy, are converted to triglycerides and stored as fat if not used for metabolic energy.

Triglycerides have been linked to an increased risk of cardiovascular disease and stroke.

HYPERLIPIDEMIA:

Hyperlipidemia is where fats (lipids) are present in increased amounts in the blood stream. An elevation of cholesterol is called hypercholesterolemia. An elevation of triglycerides is called hypertriglyceridemia. An elevation of lipoproteins such as LDL and HDL is called hyperlipoproteinemia.

NORMAL VALUES:

Cholesterol:

-A cholesterol level below 200 is considered NORMAL.

-A cholesterol level between 200 and 240 is considered BORDERLINE.

-A cholesterol level above 240 is considered ELEVATED.

HDL:

-An HDL above 35 is considered NORMAL.

-An HDL below 35 is considered LOW. This is also considered an independent risk factor for heart disease. An HDL greater than 60, however, counts as a negative risk factor, indicating that it is protective.

LDL:

-An LDL below 160 is considered NORMAL.

-An LDL above 160 is considered HIGH.

TRIGLYCERIDE:

-A triglyceride level below 200 is considered NORMAL.

-A triglyceride level between 200 and 400 is considered BOEDERLINE.

-A triglyceride level between 400 and 1000 is considered HIGH.

-A triglyceride above 1000 is considered VERY HIGH.

APOLIPOPROTEIN A-1:

This is the major constituent of HDL. The higher the level of Apolipoprotein-A1, the greater the degree of protection from developing cardiovascular disease and stroke. This substance seems to be the best predictor of premature coronary event in patients who have a family history of cardiovascular disease.

APOLIPOPROTEIN B:

This is the major constituent of LDL. The higher the level, the greater the risk of developing cardiovascular disease and stroke.  Along with Apolipoprotein-A1, this is also an excellent predictor of developing a premature cardiovascular event.

OTHER LAB TESTS USED FOR RISK ASSESSMENT:

There are a number of other substances, besides these lipids, which have also been found to be associated with the development of cardiovascular disease and stroke. This appears to be due to their involvement in the development of an atherosclerotic plaque.

HOMOCYSTEINE:

It is being increasingly recognized that Homocysteine plays a role in the development of an atherosclerotic plaque, thereby increasing the risk of cardiovascular disease. Its role in plaque formation seems to be by acting as a type of molecular abrasive, causing damage to the endothelium of the arteries in the heart, and stimulating the deposition of platelets and other clotting factors involved in the formation of a plaque.

Homocysteine is a precursor in the production of methionine through an intermediate called cystathionine. This process requires folic acid, Vitamin B12, and Vitamin B6. A deficiency of these vitamins can lead to increased levels of homocysteine, and as a result, an increased risk of cardiovascular disease and stroke.

Men with very high levels of homocysteine have been found to have a risk of heart disease three times normal. This risk is independent of any of the lipid-related risk factors.

C-REACTIVE PROTEIN:

Inflammation is a complex process, involving a number of substances and occurring for a number of different reasons. Cardiovascular disease is being increasingly recognized as having an inflammatory component. C-Reactive Protein, or CRP, is a marker of the inflammatory process, associated with the production of inflammatory cytokines. CRP is now recognized as a predictor of developing cardiovascular disease, and, according to an article in the New England Journal of Medicine, this association is independent of lipid and non-lipid risk factors.

There also seems to be an association between an elevated level of CRP and previous infection with the genital bacterium Chlamydia and the ulcer-causing bacterium Helicobacter Pylori.

FIBRINOGEN:

Fibrinogen is one of the many factors involved in the formation of a clot, or thrombus, and is elevated in a variety of infectious, inflammatory, and traumatic conditions. Its role in the formation of a plaque, and in the formation of a clot within a plaque, is by promoting platelet aggregation and injury to the vascular endothelium. The higher the level of fibrinogen, the higher the risk of cardiovascular disease. Fibrinogen is known to be increased by smoking, obesity, inflammation, stress, birth control pills, and aging.

BODY COMPOSITION ANALYSIS:

Body composition analysis is one of the measurements of overall physical fitness. Determination of Body composition allows for the determination of obesity and overweight. Obesity, as mentioned above, is considered a major risk factor for cardiovascular disease.

The two primary methods of determination of Body composition are the Body Mass Index (BMI) and the determination of the percent body fat. An older method of determination was the waist-to-hip ratio (WHR), but this is no longer recommended by the American Heart Association.

-BODY MASS INDEX (BMI):

The BMI is the expression of the amount of body weigh relative to height. At Nature’s Healthcare, we have charts that can be used to determine your BMI. You can compute your BMI with the following formula:

-Multiply your weight in lbs. by 705.

-Divide this by your height in inches.

-Then again, divide this by your height in inches.

A BMI between 25 and 30 is considered OVERWEIGHT.

A BMI over 30 is considered OBESE.

A BMI over 40 is considered EXTREME OBESITY.

-BODY FAT DETERMINATION:

By using an infrared sensor, a measurement can be made allowing determination of the percent body fat, which also allows for the determination of obesity. At Nature’s Healthcare, we can measure for you your percent body fat.

WHO SHOULD BE SCREENED OR TESTED?

The guidelines below are those put forth by the National Cholesterol Education Project (NCEP), which are supported by the American Heart Association. The recommendations for testing are:

-For all adults 20 years of age and older: Measure total cholesterol and HDL with risk factor assessment every five years.

-Measure LDL if:

-Total cholesterol is greater than 240.

-Total cholesterol is greater than 200 with 2 or more risk factors.

-HDL is less than 35.

Periodic screening is recommended through age 75. After age 75, testing is individualized based on assessment of risk factors. At this age, the benefits of routine testing become less clear.

More frequent testing than every 5 years would be recommended for patients who:

-Have more than 2 non-lipid risk factors (smoking, elevated CRP, etc.).

-Are at low risk, but have potentially changing cholesterol levels, such as perimenopausal women, or patients with significant changes in body weight, life-style, etc.

-Have a cholesterol that is near a treatment threshold, which might change sooner than 5 years.

Triglyceride testing: triglycerides are not generally measured in screening, as an isolation elevation of triglycerides does not seem to be an independent risk factor for cardiovascular disease. As well, such an isolated elevation is uncommon, except in patients with an inherited metabolic abnormality such as familial hypertriglyceridemia, where triglycerides are found to be very high. Triglyceride testing is generally done when cholesterol-lowering drug therapy is being considered, as the triglyceride level is used in the drug selection process.

The non-lipid factors such a CRP, homocysteine, and fibrinogen can be tested for on an individual basis on the basis of other risk factors and family history.

If the results of testing are abnormal, intervals for subsequent testing are individualized, and are timed so as to re-evaluate the success of intervention and treatment strategies.

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