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FAQs

Why should my lab enroll in the LSP?

The LSP can ensure that lipid, lipoprotein, and apolipoprotein measurements are accurate and comparable across long-term clinical trials and cardiovascular disease-related studies.

The primary objective of the CDC-LSP is to provide laboratories with the opportunity to standardize their analysis of total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), apolipoprotein A-I (apo A-I), and apolipoprotein B (apo B). Standardization ensures that the results of all clinical trials and population studies are comparable and traceable to well-defined standards.

Which labs should enroll in the LSP?

The CDC-LSP is available to the following types of US and international laboratories:

  1. Laboratories supporting epidemiologic studies and clinical trials
  2. Lipid research laboratories
  3. State/local public health laboratories
  4. Reference laboratories
  5. International lipid laboratories supporting epidemiologic and clinical trials
How can my laboratory enroll in the LSP?

Request an application packet from CDC and submit the completed application for approval. Please contact us for more information.

What are CDC's reference materials?

CDC reference materials are prepared from human serum according to Clinical and Laboratory Standards Institute (CLSI) guideline C37-A (Preparation and Validation of Commutable Frozen Human Serum Pools as Secondary Reference Materials for Cholesterol Measurement Procedures; Approved Guideline (6) from the Clinical and Laboratory Standards Institute (CLSI - formerly the National Committee on Clinical Laboratory Standards, or NCCLS) (5). Portions of the sterile, filtered serum are dispensed into glass vials, which are sealed and frozen at -70°C.

What methods constitute the accuracy base for lipids and lipoproteins?

The National Cholesterol Education Program (NCEP) has recommended that CDC reference measurement procedures (RMPs) be used as the accuracy base for measuring TC, HDLC cholesterol, LDLC, and TG. The Abell-Kendall (AK) RMP for cholesterol (the AK method) and the ultracentrifugation method for HDLC have been accepted as reference measurement procedures of higher order by the Joint Committee for Traceability in Laboratory Medicine. The AK method is the basis for quantification of cholesterol in the reference methods for HDLC and LDLC.

CDC's Lipid Reference Laboratory has developed a gas chromatography isotope dilution mass spectrometric (GC-IDMS) method to measure total glycerides (11). Total glycerides are defined as the sum of tri-, di-, and monoglycerides plus any free glycerol and provides measurements comparable to those of the National Institute of Standards and Technology's (NIST) primary RMP for TG, which is also based on IDMS. Total glycerides represent the analytical species measured by most clinical laboratories using enzymatic methods for triglycerides. CDC does not measure free glycerol, thus measurements of net (or glycerol blanked) triglycerides are not provided.

The International Federation of Clinical Chemistry and Laboratory Medicine's (IFCC) Committee on Apolipoproteins has established nephelometric methods at Northwest Lipid Metabolism and Diabetes Research Laboratories as designated comparison methods for apolipoproteins A-I and B (22).

Does participation in the LSP satisfy the federal regulatory requirements as stated in the Clinical Laboratory Improvement Amendments of 1988 (CLIA-88)?

No, participation in the LSP does not satisfy CLIA-88 requirements for testing of TC, HDL cholesterol, or TG. The LSP is not approved by the Centers for Medicare & Medicaid Services as a proficiency testing provider. Peer-group comparisons, such as the College of American Pathologists surveys, do meet federal regulatory requirements for clinical labs, but these surveys do not provide the same information that the LSP provides to laboratories supporting clinical trials and epidemiologic studies. The LSP is an accuracy-based program using commutable testing materials (13, 14).

What are matrix effects?

A matrix effect is the influence of a property of the sample, independent of the presence of the analyte, on the measurement and thereby on the value of the measurable quantity of that analyte. For instance, lipoprotein complexes modified during preparation and/or storage of reference materials can produce a different measurement signal than what would otherwise be expected from the native form of the analyte (12, 13, 14, 15).

What are acceptable performance criteria in the LSP?
Criteria for Acceptable Performance for the CDC-LSP Lipid Standardization Program
Expressed in mg/dL
Analyte Concentration Range of CDC Pool Maximum Allowable Bias Maximum Allowable Standard Deviation
HDLC <40.0
≥40.0
0.05 (RV)
0.05 (RV)
1.7
0.04 (RV)
TC 100-149.9
>149.9
0.03 (RV)
0.03 (RV)
4.0
0.03
TG 0.0-88.0
>88-176.0
>176.0-220.0
>220
9
10
11
0.05 (RV)
7
8
10
0.05 (RV)
Criteria for Acceptable Performance for the CDC-LSP Lipid Standardization Program
Expressed in mmol/L
Analyte Concentration Range of CDC Pool Maximum Allowable Bias Maximum Allowable Standard Deviation
HDLC (mmol/L) <1.03
≥1.03
0.05 (RV)
0.05 (RV)
0.0440
0.04 (RV)
TC (mmol/L) 2.586-3.877
>3.877
0.03 (RV)
0.03 (RV)
0.103
0.03 (RV)
TG (mmol/L) 0.00-0.994
>0.994-1.989
>1.989-2.486
>2.486
0.102
0.113
0.124
0.05 (RV)
0.079
0.090
0.113
0.05 (RV)

There are no established criteria for acceptable performance for apolipoproteins A-I and B.

If my laboratory uses more than one analytical system to measure lipid and lipoprotein study samples, will these systems need to be standardized separately?

Yes. All systems used to measure lipids, lipoproteins,and apolipoproteins in study samples must be standardized separately to qualify as "standardized systems."

Are the criteria for acceptable performance for the CDC-LSP Lipid Standardization Program for TG changed now that target values are determined by GC-IDMS ?

No. The criteria provided are not affected. They are based on NCEP-recommended clinical decision points and are not method dependent.


 
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