HDL or “good” cholesterol is a common laboratory value used by clinicians to determine a patient’s risk of heart disease. Higher HDL cholesterol levels are desirable and associated with a lower risk in heart disease. Some researchers believe that high-density lipoproteins (HDL) scavenge cholesterol from the bloodstream and arterial plaques, transporting them to the liver for elimination. Although HDL cholesterol can be directly measured from a blood sample, it is possible to estimate the HDL value from other cholesterol and lipid values when the HDL level is not directly given.
Cholesterol Testing
Since an increase in cholesterol production can occur immediately after meals, patients are often asked to refrain from eating for 9 to 12 hours prior to a clinic appointment for cholesterol testing. Although food intake is restricted, it is appropriate to drink sufficient amounts of water.
At the clinic, a sample of blood will be drawn and a lipid panel ordered. Besides routine physician visits, lipid panels are often conducted while patients are admitted in a hospital.
Lipid Panel
It can take anywhere between a few hours to a few days to obtain the results of a lipid panel. The laboratory report may contain values for some, or all of the following:
- TC (Total Cholesterol)
- LDL (Low density lipoproteins)
- HDL (High density lipoproteins)
- Triglycerides
- Non-HDL
- VLDL (Very low density lipoproteins)
HDL Cholesterol
In most cases, the HDL value will be directly reported in the results of the lipid panel. According to the most recent ATP III lipid guidelines from the National Institutes of Health, optimal HDL levels are above 60 mg/dL. HDL values below 40 mg/dL are considered low and places patients at increased risk for heart disease.
Calculating HDL
In some instances, HDL levels may not be directly reported by the lipid panel. Fortunately, HDL can be calculated using the following formula:
HDL = TC-(LDL +VLDL)
The term (triglycerides/5) can be substituted for VLDL in the above equation when VLDL values are not directly available.
Calculate Cholesterol Ratio
An important indicator of the risk of heart disease is the total cholesterol to HDL ratio. Lower ratios are desirable and associated with lower risk. For instance, a ratio of 5 places patients at average risk for heart disease, while a ratio of 10 doubles that risk. To calculate the cholesterol ratio, simply divide total cholesterol by HDL.
Certain medications and health conditions can affect lipid levels within the body. Always make your physician aware of any known health conditions and medications you are taking Patients should also speak to their physician regarding the results of the lipid panel to determine whether treatment or lifestyle modifications are needed.
Disclaimer: The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
References:
- Harvard Health Publications: “Which Cholesterol Test Should You Get?” (Accessed December 1, 2010).
- Lab Tests Online: ‘Lipid Profile” (Accessed December 1, 2010).
- National Institutes of Health: “ATP III Guidelines” (Accessed December 1, 2010).
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