Low-density Lipoprotein Cholesterol (Direct)

Also known as: Direct LDL, Direct LDLC, LDL Cholesterol, Direct, LDLC, Direct

Clinical Use

Use

For the direct determination of LDL cholesterol in nonfasting patients or in patients whose fasting triglycerides are >400 mg/dL, where the estimation of LDL by calculation may not be possible or may lead to inaccuracies. LDL cholesterol measurement, in conjunction with other lipid measurements, has been shown to be useful in assessing the risk of coronary heart disease (CHD). The National Cholesterol Education Program (NCEP)1 has stated that LDL cholesterol should be the “key index” in determination of CHD risk. Laboratory estimation of LDL cholesterol is most commonly determined by the use of formulas, such as the Friedewald formula.2 Use of this formula is limited to fasting samples with triglycerides <400 mg/dL. Triglyceride values between 250−400 mg/dL may also be associated with errors in LDL cholesterol estimation by calculation which, in turn, can lead to misclassification of the patient in regard to the NCEP guidelines.3

Special Instructions

Not provided.

Limitations

The NCEP guidelines for interpretation are based on serum values, and when classifying patients, serum or serum equivalent values should be used. This method shows no significant interference from hemolysis up to 10.0 g/L hemoglobin, bilirubin up to 30 mg/dL, and triglycerides up to 1200 mg/dL. Abnormal liver function can affect lipid metabolism, limiting the diagnostic value of HDL and LDL results in patients with hepatic disorders. There is a limitation when using anticoagulants containing citrate, which can cause sample rejection.

Test Details

Methodology

Automated Analyzer (Clinical Chemistry)

Biomarkers

LDL Cholesterol

Analyte

LDL Cholesterol (Direct)

Concentration / Level • Quantitative (Continuous) (e.g., copies/mL, % expression)

LOINC Codes

Order Codes

18262-6 - LDLc SerPl Direct Assay-mCnc

Result Codes

18262-6 - LDLc SerPl Direct Assay-mCnc

Result Turnaround Time

1 day

Specimen

Serum

Volume

1 mL

Minimum Volume

0.7 mL

Container

Red-top tube, gel-barrier tube

Collection Instructions

Separate serum or plasma from cells within 45 minutes of collection.

Patient Preparation

Patients are not required to fast prior to blood collection. Nonfasting and fasting samples can be used. Nonfasting results are slightly lower than fasting results.