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LDL Cholesterol

LDL Cholesterol

Test Highlight

LDL Cholesterol

  

Clinical Use

  • Assess risk for coronary heart disease (CHD; primary or secondary)

  • Monitor nondrug or drug therapy

Clinical Background

LDL cholesterol testing is an important part of a CHD prevention strategy. It is used to assess the risk of CHD and to monitor patients who are at increased risk. Furthermore, LDL cholesterol is used to monitor patients with prior CHD, other atherosclerotic disease, or diabetes mellitus.

LDL cholesterol is the primary target of therapy. Follow-up LDL cholesterol determination should be made 4 to 6 weeks after initiating drug therapy and again at 3 months. A minimum of 2 lipoprotein determinations is essential for evaluating the efficacy of a given drug dose. The mean of these 2 determinations and a careful assessment of drug adherence should be used to judge the efficacy of drug treatment. After the target LDL cholesterol concentration has been achieved, patients should be followed up every 4 months, or more frequently depending on the drug being used, to monitor cholesterol levels and possible side effects. See Markers of Lipidemia for additional information.

Method

The calculated LDL cholesterol relies on a calculation using 3 separate measurements: total cholesterol, HDL cholesterol, and triglycerides. The calculated LDL cholesterol is still considered an excellent initial test and is reliable and appropriate in most instances. However, if the triglycerides are abnormally high (ie, >400 mg/dL) or the patient has not appropriately fasted (recommended fast is 12 hours), then the calculated LDL cholesterol will be artificially low or non-reportable.

In contrast, the direct LDL cholesterol assay does not rely on a calculation. When an accurate and precise LDL cholesterol measurement is required, direct measurement provides an alternative. Direct measurement provides a reliable result even when triglyceride levels are up to 1000 mg/dL. Further, the direct LDL cholesterol assay has been correlated with the CDC-accepted reference method. Thus, results can be related to the epidemiologic data that have been generated for the assessment of CHD risk and the monitoring of therapy to reduce that risk.

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Interpretive Information

The target LDL cholesterol level varies according to the risk profile of the patient (Table). Typically, therapeutic lifestyle changes (TLC) are the first choice for moderate elevations in LDL cholesterol. Drug therapy may be the first choice in individuals with higher cholesterol levels and those who do not respond to TLC.

Table. Low-Density Lipoprotein-Cholesterol (LDL) Goals1
Risk Category LDL, mg/dL
Goal Start TLC

Consider Drug Therapy

High risk:

CHD or CHD risk equivalent

10-year CHD risk >20%

<100a

≥100

≥100b,c

 

Moderately high risk:

≥2 risk factors for CHD
10-year CHD risk 10%-20%

<130a

≥130

≥130 (optional at 100-129)c

Moderate risk:

≥2 risk factors for CHD

10-year CHD risk <10%

<130

≥130

≥160

Low risk:

<2 risk factors for CHD

<160d

≥160

≥190 (optional at 160-189)c

CHD, coronary heart disease; TLC, therapeutic lifestyle changes

a For moderately high-risk persons, an LDL goal of <100 mg/dL is an option; for patients with very high risk, a goal of <70 mg/dL should be considered. TLC should be considered for all individuals with moderately high or high CVD risk who have risk factors related to lifestyle, regardless of LDL levels.
b American Heart Association guidelines suggest that drug therapy (preferably with a statin) should be initiated in combination with lifestyle therapy in high-risk women with LDL levels ≥100 mg/dL; statin therapy should also be initiated in high-risk women with LDL levels <100 mg/dL unless contraindicated.
c Factors favoring drug initiation include 1) a severe single risk factor: heavy cigarette smoking, poorly controlled hypertension, a strong family history of premature CHD, or very low high-density lipoprotein-cholesterol; 2) multiple life-habit risk factors or emerging risk factors; and 3) 10-year CHD risk approaching 10%.
d American Heart Association guidelines indicate that the optimal level in women is <100 mg/dL.
Note: Individuals with high or moderately high risk with lifestyle-related risk factors should initiate TLC to address those risk factors, regardless of LDL level.

References

  1. Executive Summary of The Third Report of The National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA. 2001;285:2486-2509.

 

Content reviewed 12/2012
 

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