Procedures for Joining CRMLN

Cholesterol Reference Method Laboratory Network (CRMLN) members provide reference measurement services to laboratories and test manufacturers using CDC’s standardization protocols. Network laboratories can be associated with medical schools, state health departments, and nonprofit organizations. CRMLN members are encouraged to provide reference measurement services for total cholesterol, HDL-C, LDL-C, and total glycerides.

Non-government laboratories interested in joining CRMLN must provide CDC with documentation indicating support from the professional clinical community, or other appropriate organizations, in their country.

CRMLN member laboratories must be able to:

  • Operate and maintain the reference measurement procedures used in CDC’s Standardization Programs
  • Participate in the biannual CRMLN studies
  • Provide certification services to the clinical and research community for the analytes used in CDC’s standardization programs, in compliance with the CDC standardization protocols
  • Share reference measurement procedures with other network members

A candidate laboratory must submit an official request on laboratory letterhead to to apply for network membership. The request should state the analytes and reference methods the laboratory would like to provide certification services for, and documentation demonstrating their ability to perform the tasks outlined above. Questions related to membership can also be sent to

A qualified candidate laboratory must successfully pass two consecutive challenges that demonstrate its ability to meet CRMLN network performance criteria. The analytical performance criteria for CRMLN laboratories (see table below) are more stringent than those for clinical laboratories measuring patient samples. This enables CRMLN laboratories to appropriately assess the measurement accuracy and precision of tests used in patient care.

Analytical Performance Criteria for CRMLN Member Laboratories

For each analyte, CRMLN members are evaluated for agreement with the criteria presented in the table:

Analytical Performance Criteria for CRMLN Member Laboratories
Bias1 ≤ 1% ≤ 2% ≤ 1 mg/dL
Imprecision ≤ 1% ≤ 1.5% ≤ 1 SD

1bias to CDC reference measurement procedure

TC: Total Cholesterol
HDL-C: High Density Lipoprotein Cholesterol
LDL-C: Low Density Lipoprotein Cholesterol

Upon successfully passing the challenges, the laboratory acquires CRMLN membership and participates in fulfilling the network roles and responsibilities.

Procedures for Certification of Manufacturers


Use of trade names is for identification only and does not constitute endorsement by the CDC or the U.S. Department of Health and Human Services.