Cholesterol, HDL and LDL

Synonym/acronym: α₁-Lipoprotein cholesterol, high-density cholesterol, HDLC, and β-lipoprotein cholesterol, low-density cholesterol, LDLC.

Common use

To assess risk and monitor for coronary artery disease.

Specimen

Serum (2 mL) collected in a gold-, red-, or red/gray-top tube.

Normal findings

(Method: Spectrophotometry)

HDLC	Conventional Units	SI Units (Conventional Units × 0.0259)
Birth	6–56 mg/dL	0.16–1.45 mmol/L
Children, adults, and older adults
Desirable	Greater than 60 mg/dL	Greater than 1.55 mmol/L
Acceptable	40–60 mg/dL	1–1.55 mmol/L
Low	Less than 40 mg/dL	Less than 1 mmol/L

LDLC	Conventional Units	SI Units (Conventional Units × 0.0259)
Optimal	Less than 100 mg/dL	Less than 2.59 mmol/L
Near optimal	100–129 mg/dL	2.59–3.34 mmol/L
Borderline high	130–159 mg/dL	3.37–4.11 mmol/L
High	160–189 mg/dL	4.14–4.9 mmol/L
Very high	Greater than 190 mg/dL	Greater than 4.92 mmol/L

	NMR LDLC Particle Number	NMR LDLC Small Particle Size
High-risk CAD	Less than 1,000 nmol/L	Less than 850 nmol/L
Moderately high-risk CAD	Less than 1,300 nmol/L	Less than 850 nmol/L

CAD, coronary artery disease; NMR, nuclear magnetic resonance.

Description

High-density lipoprotein cholesterol (HDLC) and low-density lipoprotein cholesterol (LDLC) are the major transport proteins for cholesterol in the body. It is believed that HDLC may have protective properties in that its role includes transporting cholesterol from the arteries to the liver. LDLC is the major transport protein for cholesterol to the arteries from the liver. LDLC can be calculated using total cholesterol, total triglycerides, and HDLC levels. Beyond the total cholesterol, HDL and LDL cholesterol values, other important risk factors must be considered. In November 2013, new guidelines for the prevention of cardiovascular disease (CVD) were developed by the American College of Cardiology (ACC) and the American Heart Association (AHA) in conjunction with members of the National Heart, Lung, and Blood Institute’s (NHLBI) ATP IV Expert Panel. The updated, evidence-based guidelines redefine the condition of concern as atherosclerotic cardiovascular disease (ASCVD) and expand ASCVD to include CVD, stroke, and peripheral artery disease. Some of the important highlights include the following:

Movement away from the use of LDL cholesterol targets in determining treatment with statins. Recommendations that focus on selecting (a) the patients that fall into four groups most likely to benefit from statin therapy, and (b) the level of statin intensity most likely to affect or reduce development of ASCVD.
Development of a new 10-yr risk assessment tool based on findings from a large, diverse population. Evidence-based risk factors include age, sex, ethnicity, total cholesterol, HDLC, blood pressure, blood-pressure treatment status, diabetes, and current use of tobacco products.
Recommendations for aspects of lifestyle that would encourage prevention of ASCVD to include adherence to a Mediterranean-style or DASH (Dietary Approaches to Stop Hypertension)-style diet; dietary restriction of saturated fats, trans fats, sugar, and sodium; and regular participation in aerobic exercise. The guidelines contain reductions in body mass index (BMI) cutoffs for men and women designed to promote discussions between HCPs and their patients regarding the benefits of maintaining a healthy weight.
Recognition that additional biological markers, such as family history, high-sensitivity C-reactive protein, ankle-brachial index (ABI), and coronary artery calcium (CAC) score, may be selectively used with the assessment tool to assist in predicting and evaluating risk.
Recognition that other biomarkers such as apolipoprotein B, eGFR, creatinine, lipoprotein (a) or Lp(a), and microalbumin warrant further study and may be considered for inclusion in future guidelines.

Studies have shown that CAD is inversely related to LDLC particle number and size. The nuclear magnetic resonance (NMR) lipid profile uses NMR imaging spectroscopy to determine LDLC particle number and size in addition to measurement of the traditional lipid markers.

HDLC levels less than 40 mg/dL in men and women represent a coronary risk factor. There is an inverse relationship between HDLC and risk of CAD (i.e., lower HDLC levels represent a higher risk of CAD). Levels of LDLC in terms of risk for CAD are directly proportional to risk and vary by age group. The LDLC can be estimated using the Friedewald formula:

LDLC = (Total Cholesterol) − (HDLC) − (VLDLC)

Very-low-density lipoprotein cholesterol (VLDLC) is estimated by dividing the triglycerides (conventional units) by 5. Triglycerides in SI units would be divided by 2.18 to estimate VLDLC. It is important to note that the formula is valid only if the triglycerides are less than 400 mg/dL or 4.52 mmol/L.

This procedure is contraindicated for

N/A

Indications

Determine the risk of cardiovascular disease
Evaluate the response to dietary and drug therapy for hypercholesterolemia
Investigate hypercholesterolemia in light of family history of cardiovascular disease

Potential diagnosis

Although the exact pathophysiology is unknown, cholesterol is required for many functions at the cellular and organ levels. Elevations of cholesterol are associated with conditions caused by an inherited defect in lipoprotein metabolism, liver disease, kidney disease, or a disorder of the endocrine system. Decreases in cholesterol levels are associated with conditions caused by enzyme deficiencies, malnutrition, malabsorption, liver disease, and sudden increased utilization.

HDLC increased in

Alcoholism Biliary cirrhosis Chronic hepatitis Exercise Familial hyper-α-lipoproteinemia

HDLC decreased in

Abetalipoproteinemia Cholestasis Chronic renal failure Fish-eye disease Genetic predisposition or enzyme/cofactor deficiency Hepatocellular disorders Hypertriglyceridemia Nephrotic syndrome Obesity Premature CAD Sedentary lifestyle Smoking Tangier’s disease Syndrome X (metabolic syndrome) Uncontrolled diabetes

LDLC increased in

Anorexia nervosa Chronic renal failure Corneal arcus Cushing’s syndrome Diabetes Diet high in cholesterol and saturated fat Dysglobulinemias Hepatic disease Hepatic obstruction Hyperlipoproteinemia types IIA and IIB Hypothyroidism Nephrotic syndrome Porphyria Pregnancy Premature CAD Syndrome X (metabolic syndrome) Tendon and tuberous xanthomas

LDLC decreased in

Acute stress (severe burns, illness) Chronic anemias Chronic pulmonary disease Genetic predisposition or enzyme/cofactor deficiency Hyperthyroidism Hypolipoproteinemia and abetalipoproteinemia Inflammatory joint disease Myeloma Reye’s syndrome Severe hepatocellular destruction or disease Tangier disease

Critical findings

N/A

Interfering factors

Drugs that may increase HDLC levels include albuterol, anticonvulsants, cholestyramine, cimetidine, clofibrate and other fibric acid derivatives, estrogens, ethanol (moderate use), lovastatin, niacin, oral contraceptives, pindolol, pravastatin, prazosin, and simvastatin.
Drugs that may decrease HDLC levels include acebutolol, atenolol, danazol, diuretics, etretinate, interferon, isotretinoin, linseed oil, metoprolol, neomycin, nonselective β-adrenergic blocking agents, probucol, progesterone, steroids, and thiazides.
Drugs that may increase LDLC levels include androgens, catecholamines, chenodiol, cyclosporine, danazol, diuretics, etretinate, glucogenic corticosteroids, and progestins.
Drugs that may decrease LDLC levels include aminosalicylic acid, cholestyramine, colestipol, estrogens, fibric acid derivatives, interferon, lovastatin, neomycin, niacin, pravastatin, prazosin, probucol, simvastatin, terazosin, and thyroxine.
Some of the drugs used to lower total cholesterol and LDLC or increase HDLC may cause liver damage.
Grossly elevated triglyceride levels invalidate the Friedewald formula for mathematical estimation of LDLC; if the triglyceride level is greater than 400 mg/dL, the formula should not be used.
Fasting before specimen collection is highly recommended. Ideally, the patient should be on a stable diet for 3 wk and fast for 12 hr before specimen collection.
Failure to follow dietary restrictions before the procedure may cause the procedure to be canceled or repeated.

Nursing Implications and Procedure

Pretest

Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
Patient Teaching: Inform the patient this test can assist with evaluation of cholesterol level.
Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
Obtain a history of the patient’s cardiovascular system and results of previously performed laboratory tests and diagnostic and surgical procedures. The presence of other risk factors, such as family history of heart disease, smoking, obesity, diet, lack of physical activity, hypertension, diabetes, previous myocardial infarction, and previous vascular disease, should be investigated.
Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
Instruct the patient to fast for 12 hr before specimen collection. Protocols may vary among facilities.
Confirm with the requesting health-care provider (HCP) that the patient should withhold medications known to influence test results, and instruct the patient accordingly.
Note that there are no fluid restrictions unless by medical direction.

Intratest

Ensure that the patient has complied with dietary and medication restrictions as well as other pretesting preparations; ensure that food has been restricted for at least 12 hr prior to the procedure.
Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
Instruct the patient to resume usual diet, fluids, and medications, as directed by the HCP.
Nutritional Considerations: Decreased HDLC level and increased LDLC level may be associated with CAD. Nutritional therapy is recommended for the patient identified to be at risk for developing CAD or for individuals who have specific risk factors and/or existing medical conditions (e.g., elevated LDL cholesterol levels, other lipid disorders, insulin-dependent diabetes, insulin resistance, or metabolic syndrome). Other changeable risk factors warranting patient education include strategies to encourage patients, especially those who are overweight and with high blood pressure, to safely decrease sodium intake, achieve a normal weight, ensure regular participation in moderate aerobic physical activity three to four times per week, eliminate tobacco use, and adhere to a heart-healthy diet. If triglycerides also are elevated, the patient should be advised to eliminate or reduce alcohol. The 2013 Guideline on Lifestyle Management to Reduce Cardiovascular Risk published by the ACC and AHA in conjunction with the NHLBI recommends a “Mediterranean”-style diet rather than a low-fat diet. The new guideline emphasizes inclusion of vegetables, whole grains, fruits, low-fat dairy, nuts, legumes, and nontropical vegetable oils (e.g., olive, canola, peanut, sunflower, flaxseed), along with fish and lean poultry. A similar dietary pattern known as the DASH diet makes additional recommendations for the reduction of dietary sodium. Both dietary styles emphasize a reduction in consumption of red meats, which are high in saturated fats and cholesterol, and other foods containing sugar, saturated fats, trans fats, and sodium.
Social and Cultural Considerations: Numerous studies point to the prevalence of excess body weight in American children and adolescents. Experts estimate that obesity is present in 25% of the population ages 6 to 11 yr. The medical, social, and emotional consequences of excess body weight are significant. Special attention should be given to instructing the child and caregiver regarding health risks and weight-control education.
Recognize anxiety related to test results, and be supportive of fear of shortened life expectancy. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate. Educate the patient regarding access to counseling services. Provide contact information, if desired, for the American Heart Association (www.americanheart.org) or the NHLBI (www.nhlbi.nih.gov).
Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

Related tests include antiarrhythmic drugs, apolipoprotein A and B, AST, ANP, blood gases, BNP, calcium (total and ionized), cholesterol total, CT cardiac scoring, CRP, CK and isoenzymes, echocardiography, glucose, glycated hemoglobin, Holter monitor, homocysteine, ketones, LDH and isoenzymes, lipoprotein electrophoresis, magnesium, MRI chest, MI scan, myocardial perfusion heart scan, myoglobin, PET heart, potassium, triglycerides, and troponin.
Refer to the Cardiovascular System table at the end of the book for related tests by body system.

See Cholesterol, HDL and LDL