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Test ID: LDL
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LDL
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Useful For
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Useful in assessing and managing the risk of coronary heart disease (CHD) in conjunction with other lipid measurements.
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Method name and description
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Homogeneous enzymatic colorimetric assayCholesterol esters and free cholesterol in LDL are measured on the basis of a cholesterol enzymatic method using cholesterol esterase and cholesterol oxidase in the presence of surfactants which selectively solubilize only LDL. The enzyme reactions to the lipoproteins other than LDL are inhibited by surfactants and a sugar compound. Cholesterol in HDL, VLDL and chylomicron is not determined.In the presence of oxygen, cholesterol is oxidized by cholesterol oxidase to Δ4‑cholestenone and hydrogen peroxide.
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Clinical information
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Low Density Lipoproteins (LDL) play a key role in causing and progression of atherosclerosis and, in particular, coronary sclerosis. The LDLs are derived from VLDLs (Very Low-Density Lipoproteins) rich in triglycerides by the action of various lipolytic enzymes and are synthesized in the liver. The elimination of LDL from plasma takes place mainly by liver parenchymal cells via specific LDL receptors. Elevated LDL concentrations in blood and an increase in their residence time coupled with an increase in the biological modification rate results in the destruction of the endothelial function and a higher LDL-cholesterol uptake in the monocyte/macrophage system as well as by smooth muscle cells in vessel walls. The majority of cholesterol stored in atherosclerotic plaques originates from LDL. The LDL cholesterol value is the most powerful clinical predictor among all of the single parameters with respect to coronary atherosclerosis. Therefore, therapies focusing on lipid reduction primarily target the reduction of LDL cholesterol which is then expressed in an improvement of the endothelial function, prevention of atherosclerosis and reducing its progression as well as preventing plaque rupture.
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Specimen type / Specimen volume / Specimen container
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Specimen type: Serum, Plasma
Minimum volume of sample: 1 mL
Serum: Plain tube (red or yellow top)
Plasma: Li‑heparin tube
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Collection instructions / Special Precautions / Timing of collection
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Collect blood by standard venipuncture techniques as per specimen requirements. When processing samples in primary tubes (sample collection systems), follow the instructions of the tube manufacturer.
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Storage and transport instructions
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Storage: 7 days at 2 – 8°C
12 months – 20 °C
12 months at ‑70°C
Transport: 2-25°C
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Specimen Rejection Criteria
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Grossly hemolyzed and icteric samples, wrong collection container, insufficient sample.
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Biological reference intervals and clinical decision values
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Optimal
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< 2.59 mmol/L
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Near optimal/ above optimal:
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2.59- 3.34 mmol/L
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Borderline high:
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3.37-4.12 mmol/L
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High:
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4.14- 4.89 mmol/L
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Very High:
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> 4.92 mmol/L
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Factors affecting test performance and result interpretation
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Abnormal liver function affects lipid metabolism; consequently HDL and LDL results are of limited diagnostic value. In some patients with abnormal liver function, the LDL‑cholesterol result is significantly negatively biased versus beta quantification results.
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Turnaround time / Days and times test performed / Specimen retention time
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Daily (24/7)
Turn-around time:
Routine: One working day
Specimen Retention: 4 days
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