LDL Cholesterol Test

Definition
Purpose
Description
Recommended dosage
Precautions
Side effects
Interactions

Definition

An LDL test measures the low density lipoprotein fraction of a person’s total cholesterol.

Purpose

The purpose of an LDL test is to evaluate an individual’s risk of cardiovascular (heart) disease.

Description

The LDL test is a component of a lipid profile. A lipid profile includes four blood tests: total cholesterol, HDL cholesterol, LDL cholesterol and triglycerides.

LDL stands for low density lipoproteins. It is also known as the so-called bad cholesterol. It slowly accumulates on the inner walls of arteries. This buildup is known as plaque. Over time, it creates a condition known as atherosclerosis.

Dietary fats, including cholesterol, are absorbed from the small intestines. They are converted into triglycerides, which are then packaged into lipoproteins. All of these products are transported into the liver by chylomicrons. After a fast (not eating) lasting at least 12 hours, chylomicrons are absent from the bloodstream. This is the reason why persons that are having an LDL test must fast overnight.

A healthy LDL level is 129 mg/dL or less (in the optimal or near optimal ranges).

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?

• LDL cholesterol tests are typically ordered by a family doctor, internist or geriatrician.
• A blood sample is usually obtained by a nurse, phlebotomist or medical technologist.
• The blood sample is tested or processed by a medical technologist.
• Results are usually reviewed, returned to the person being tested and interpreted by the physician initially ordering the LDL test.

• Optimal: Less than 100 mg/dL
• Near optimal: 100-129 mg/dL
• Borderline high: 130-159 mg/dL
• High: 160-189 mg/dL
• Very high: 190 mg/dL and higher

Pharmaceutical interventions are based, in part, on LDL test values.

An optimal range is defined as less than 70mg/dL for persons with a history of heart disease or those at very high risk for atherosclerotic disease.

Ranges for laboratory values may vary slightly among different laboratories.

Recommended dosage

LDL cholesterol testing is a component of a lipid profile. A lipid profile can be ordered at any time. Routine lipid profiles that are used to monitor the effectiveness of drugs intended to reduce serum cholesterol are usually performed every three months.

Precautions

A fast (not eating) for a minimum of 12 hours before drawing blood contributes to a more accurate measurement of lipids in the blood. No other precautions are needed.

At the time of drawing blood, the only precaution needed is to clean the venipuncture site with alcohol.

Side effects

The most common side effects of an LDL test are minor bleeding (hematoma) or bruising at the site of venipuncture.

QUESTIONS TO ASK YOUR DOCTOR

• Why are LDL cholesterol tests needed?
• What do the results indicate for my health?
• What treatment options do I have?

Interactions

There are no interactions for an LDL test.

Resources

BOOKS

Fischbach, F. T. and M. B. Dunning. A Manual of Laboratory and Diagnostic Tests. 8th ed. Philadelphia: Lippincott Williams & Wilkins, 2008.

McGhee, M. A Guide to Laboratory Investigations. 5th ed. Oxford, UK: Radcliffe Publishing Ltd, 2008.

Price, C. P. Evidence-Based Laboratory Medicine: Principles, Practice, and Outcomes. 2nd ed. Washington, DC: AACC Press, 2007.

Scott, M.G., A. M. Gronowski, and C. S. Eby. Tietz’s Applied Laboratory Medicine. 2nd ed. New York: Wiley-Liss, 2007.

Springhouse, A. M.. Diagnostic Tests Made Incredibly Easy!. 2nd ed. Philadelphia: Lippincott Williams & Wilkins, 2008.

PERIODICALS

Amati, L., M. Chilorio, E. Jirillo, and V. Covelli. “Early pathogenesis of atherosclerosis: the childhood obesity.” Current Pharmaceutical Design 13, no. 36 (2007): 3696–3700.

Leigh-Hunt, N., and M. Rudolf. “A review of local practice regarding investigations in children attending obesity clinics and a comparison of the results with other studies.” Child Care Health and Delivery 34, no. 1 (2008): 55–58.

Shephard, M. D., B. C. Mazzachi, and A. K. Shephard. “Comparative performance of two point-of-care analysers for lipid testing.” Clinical Laboratory 53, no. 9-12 (2007): 561–566.

Wright, J. T., S. Harris-Haywood, S. Pressel, et al. “Clinical outcomes by race in hypertensive patients with and without the metabolic syndrome: Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial.” Archives of Internal Medicine 168, no. 2 (2008): 207–217.

ORGANIZATIONS

American Association for Clinical Chemistry. http://www.aacc.org/AACC/.

American Society for Clinical Laboratory Science. http://www.ascls.org/.

American Society of Clinical Pathologists. http://www.ascp.org/.

KEY TERMS

Hematoma— A collection of blood that has entered a closed space.

Phlebotomist— Health care professional trained to obtain samples of blood.

College of American Pathologists. http://www.cap.org/apps/cap.portal.

OTHER

American Clinical Laboratory Association. “Information about clinical chemistry.” 2008 [cited February 24, 2008]. http://www.clinical-labs.org/.

Clinical Laboratory Management Association. “Information about clinical chemistry.” 2008 [cited February 22, 2008]. http://www.clma.org/.

Lab Tests On Line. “Information about lab tests.” 2008 [cited February 24, 2008]. http://www.labtestsonline.org/.

National Accreditation Agency for Clinical Laboratory Sciences. “Information about laboratory tests.” 2008 [cited February 25, 2008]. http://www.naacls.org/.

L. Fleming Fallon, Jr, MD, DrPH