Cholesterol (HDL and LDL) - plasma or serum

Last updated: Wednesday, 02, June, 2010

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Item Process
Specimen

5 mL blood in EDTA, lithium heparin or plain tube (same specimen as for total cholesterol will suffice).

Prolonged tourniquet use can artefactually increase levels by up to 20%.

See Table 1. Artefactual results.

Method

Numerous separation methods are available, including direct spectrophotometric assay or ultracentrifugation and electrophoresis.

LDL cholesterol is usually calculated rather than measured directly although this is unreliable if levels of triglyceride are >4.5 mmol/L.

The usual calculation using mmol/L for LDL cholesterol (Friedewald equation) is:
LDL cholesterol = total cholesterol - HDL cholesterol - triglyceride/2.2

Reference Interval

HDL
Female
Population reference range: 1.0-2.2 mmol/L
Therapeutic targets: >1.0 mmol/L
Male
Population reference range: 0.9-2.0 mmol/L
Therapeutic targets: >1.0 mmol/L

LDL
Population reference range: 2.0-3.4 mmol/L 
Therapeutic targets: <2.5 mmol/L.

Application

Investigation of lipid status in suspected hyperlipidaemia.

Assessment of risk for atherosclerosis, especially coronary artery disease.

Interpretation

Low levels of HDL and high levels of LDL cholesterol are associated with an increased risk of atherosclerotic vascular disease.

National guidelines generally specify specific targets.

LDL levels are reduced for up to 8 weeks with acute illness (eg, myocardial infarction, acute infection) and assays should not be performed during this time.

See also Apolipoproteins - serum.

Reference

Linton MFandFazio S. Am J Cardiol 2003; 92(1A): 19i-26i.