Low-density Lipoprotein Cholesterol (Direct)
Also known as: Direct LDL, Direct LDLC, LDL Cholesterol, Direct, LDLC, Direct
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
Patients are not required to fast prior to blood collection. Nonfasting results are slightly lower than fasting results. For this direct LDL method, a factor of 1.06 should be used to convert EDTA plasma values to serum values. Separate serum or plasma from cells within 45 minutes of collection.
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.
Methodology
Automated Analyzer (Clinical Chemistry)
Biomarkers
LOINC Codes
- 18262-6
- 18262-6
Result Turnaround Time
1 day
Related Documents
For more information, please review the documents below
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.
Storage Instructions
Room temperature
Causes for Rejection
Use of anticoagulants containing citrate
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |
| Frozen | 14 days |