Cholesterol (HDL and LDL) - plasma or serum
Last updated: Wednesday, 02, June, 2010
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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%.
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:
| Reference Interval|
Investigation of lipid status in suspected hyperlipidaemia.
Assessment of risk for atherosclerosis, especially coronary artery disease.
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.
Linton MFandFazio S. Am J Cardiol 2003; 92(1A): 19i-26i.