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LDL-Cholesterol, Direct (LDLDR)

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EPIC Test Name

LDL CHOLESTEROL, DIRECT

EPIC Code

LAB102

Specimen Requirements

plasma
Minimum Volume:0.5 mL
Collection:Collect specimens using standard laboratory procedures.
Transport:Room Temperature ASAP
Stability:Refrigerated: 7 days at 2-8 degrees C
Frozen: 12 months at -20 degrees C
Container:LT GRN
Rejection Causes:Hemolysis, lipemic,
Insufficient Sample Volume

Methods

Homogeneous Enzymatic Colorimetric

Turnaround Time

SpecimenTurnaround TimeFrequency
plasmaRoutine: 4 hours24/7

Reference Ranges

Homogeneous Enzymatic Colorimetric
All RangeUnit
<100 mg/dLmg/dL

Clinical Indications

Low Density Lipoproteins (LDL) play a key role in causing and influencing the progression of atherosclerosis and, in particular, coronary sclerosis. Low density lipoproteins (LDLs) are derived from intermediate Density Lipoproteins. LDLs are comprised of about 35-40% cholesterol esters, 5-10% cholesterol, 20% proteins (apo B), 20% phospholipids, and 10% triglycerides. LDLs delivers cholesterol from the liver to the cells of peripheral tissues or of the liver for recycle or elimination. Endocytosis occurs via binding to the specific LDL receptor. Intracellularly, LDLs are degraded by lysosomal lipase and proteases. The released cholesterol be stored as cholesterol-esters or incorporated into cell membranes. Patients lacking the LDL receptor suffer from familial hypercholestermia showing elevated total plasma cholesterol and LDL-cholesterol. Severity vary depending effect of the gene mutations and if it is homozygous vs heterozygous LDL-receptor gene mutations. It is known that the majority of cholesterol stored in atherosclerotic plaques originates from LDLs. The LDL‑cholesterol value is an important indicator of CHD risk. Therapies focusing on lipid reduction primarily target the reduction of LDL‑cholesterol for improving the endothelial function, preventing atherosclerosis and reducing its progression as well as preventing plaque rupture.

The LDL‑cholesterol concentration can be calculated according to Friedewald’s formula (mg/dL):

LDL-cholesterol = Total cholesterol – HDL-cholesterol – Triglyceride/5.0

The limitation of the Friedewald’s formula include: 1) need two cholesterol determinations (total cholesterol and HDL-cholesterol) and one triglyceride determination, 2) requirement of a serum triglyceride concentration < 400 mg/dL, 3) non-fasting samples be rejected due to high concentration of chylomicrons, and 4) not applicable to patients with lipoproteinemias. The LDL-cholesterol direct assay selectively measures LDL‑cholesterol in serum and plasma samples with a minimal effect by non-fasting sample, while meeting the 1995 NCEP goals of < 4 % total CV, bias ≤ 4 % versus reference method, and ≤ 12 % total analytical error.

NCEP recommended LDL-cholesterol < 130 mg/dL.

Additional Information

• Acetaminophen intoxications are frequently treated with N‑acetylcysteine. N‑acetylcysteine at the therapeutic concentration when used as an antidote and the Acetaminophen metabolite N‑acetyl‑p‑benzoquinone imine (NAPQI) independently may cause falsely low LDL‑C results.
• Venipuncture should be performed prior to the administration of Metamizole. Venipuncture immediately after or during the administration of Metamizole may lead to falsely low results.
• Interpretation of results should be cautioned for patients with abnormal liver function that affects lipid metabolism, therefore, HDL and LDL results.
• EDTA plasma may cause decreased values compared to serum.

Common Synonyms

Direct Low Density Cholesterol

Performed

Lab
Chemistry - Downtown

Interpretative Information

Various guidelines have different recommendation for LDL-cholesterol goal values:
The following goals are of Cleveland Clinic (https://my.clevelandclinic.org/health/articles/16866-cholesterol-guidelines--heart-health)
• < 70 mg/dL for those with heart or blood vessel disease and for other patients at very high risk of heart disease (those with metabolic syndrome)
• < 100 mg/dL for high risk patients (for example: some patients who have diabetes or multiple heart disease risk factors)
• < 130 mg/dL otherwise.

CPT

83721

LOINC

18262-6

References

1. Rifai N, Warnick GR, McNamara JR, et al. Measurement of LowDensity-Lipoprotein Cholesterol in Serum: a Status Report. Clin Chem 1992;38:150-160.
2. Naito HK, Strong JP, Scott MG, et al. Atherogenesis: current topics on etiology and risk factors. Clin Chem 1995;41:132-133.
3. Pisani T, Gebski CP, Leary ET, et al. Accurate Direct Determination of Low-density Lipoprotein Cholesterol Using an Immunoseparation Reagent and Enzymatic Cholesterol Assay. Arch Pathol Lab Med 1995;119(12):1127-35.
4. Friedewald WF, Levy RI, Frederickson DS. Estimation of the Concentration of Low-Density Lipoprotein Cholesterol in Plasma, Without Use of the Preparative Ultracentrifuge. Clin Chem 1972;18:499-502.
5. Tighe DA, Ockene IS, Reed G, et al. Calculated low density lipoprotein cholesterol levels frequently underestimate directly measured low density lipoprotein cholesterol determinations in patients with serum triglyceride levels ≤ 4.52 mmol/l: An analysis comparing the LipiDirect® magnetic LDL assay with the Friedewald calculation. Clinica Chimica Acta 2006;365:236-242.
6. Cohn JS, McNamara JR, Schaefer EJ. Lipoprotein Cholesterol Concentrations in the Plasma of Human Subjects as Measured in the Fed and Fasted States. Clin Chem 1988;34:2456-9.
7. National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). 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) final report. Circulation. 2002;106:3143-421. PMID: 12485966.
8. Bachorik PS, Ross JW. National cholesterol education program recommendations for measurement of low-density lipoprotein cholesterol: executive summary. Clin Chem 1995;41:1414-20.
9. Cooper GR, Myers GL, Smith SJ, et al. Standardization of Lipid, Lipoprotein, and Apolipoprotein Measurements. Clin Chem 1988;34(8B):B95-B105.
10. Rifai N, Dufour RD, Cooper GR. Preanalytical Variation in Lipid, Lipoprotein, and Apolipoprotein Testing. In: Rifai N, Warnick GR, Dominiczak MH, eds. Handbook of Lipoprotein Testing. 2nd ed. Washington, AACC Press; 2000. p. 161-176.

Contact Information

Chemistry - Downtown: (315)464-4460
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