Vitamin D Metabolites Quality Assurance Program

The National Institute of Standards and Technology (NIST) and the National Institutes of Health (NIH) Office of Dietary Supplements (ODS) have established a Vitamin D Metabolites Quality Assurance Program (VitDQAP). Interlaboratory comparison studies are currently directed toward the measurement of 25-hydroxyvitamin D₂ and 25-hydroxyvitamin D₃ in selected serum and plasma matrices as well as method-appropriate control materials.  Frozen or freeze-dried serum or plasma samples together with control materials are sent to laboratories biannually (winter and summer) for analysis. Results are then returned to NIST for data evaluation and tabulation. Value-assignment of the samples is based on the median of all the laboratory results, with confirmation based on measurement at NIST using two or more different methods. Consultation and troubleshooting regarding methods of analysis are also provided. A report of exercise results is sent to participants, and workshops will be scheduled to discuss results as well as methodological issues and advancements in clinically-relevant vitamin D metabolite measurements.

Standard Reference Material (SRM) 972a and SRM 2972

We recommend the use of SRM 972a Vitamin D Metabolites in Human Serum and SRM 2972 25-Hydroxyvitamin D₂ and D₃ Calibration Solutions at the outset of participation in the QA program to validate methodology and to value-assign in-house control materials. These SRMs may be purchased from the Standard Reference Materials Program at NIST (301-975-2200; fax: 301-948-3730; or e-mail: srminfo@nist.gov).

VitDQAP Exercise Workshops

VitDQAP Exercise Workshops Workshops are to be held for laboratories that measure vitamin D metabolites in human serum and plasma as part of the QA program. These workshops provide an opportunity for participants to discuss analytical methods, results of the interlaboratory comparison exercises, and other related topics. Our most recent workshop was held at the 2011 Experimental Biology meeting in Washington, DC, on April 13, 2011 as part of the NIST Micronutrients Measurement Quality Assurance Workshop. If you would like more information regarding the workshop, please contact us at vitdqap@nist.gov.  

Certificates and Reports

Reports for the first four exercises have been published:

NISTIR 7890: NIST/NIH Vitamin D Metabolites Quality Assurance Program Report of Participant Results: Winter 2010 Comparability Study (Exercise 1)

NISTIR 7891: NIST/NIH Vitamin D Metabolites Quality Assurance Program Report of Participant Results: Summer 2010 Comparability Study (Exercise 2)

NISTIR 7892: NIST/NIH Vitamin D Metabolites Quality Assurance Program Report of Participant Results: Winter 2011 Comparability Study (Exercise 3)

NISTIR 7893: NIST/NIH Vitamin D Metabolites Quality Assurance Program Report of Participant Results: Summer 2011 Comparability Study (Exercise 4).

NISTIR 7894: NIST/NIH Vitamin D Metabolites Quality Assurance Program Report of Participant Results: Winter 2012 Comparability Study (Exercise 5)

NISTIR 7895: NIST/NIH Vitamin D Metabolites Quality Assurance Program Report of Participant Results: Summer 2012 Comparability Study (Exercise 6)

An example figure from the Summer 2011 Report illustrating the 25-hydroxyvitamin D (25(OH)D_Total) levels in two study materials as determined by immunoassay (CLIA, EIA and RIA) and LC (LC-MS_n and LC-UV) methods is shown below.  

Certificates of participation can also be provided upon individual request.

CONFIDENTIALITY STATEMENT: It is our policy that participants' laboratory identification numbers remain confidential and known only to them and ourselves.

How to Join the Program

If you are interested in joining our program, please send an e-mail to vitdqap@nist.gov. There is no fee for participation.

NIST/NIH Vitamin D Metabolites Quality Assurance Program
National Institute of Standards and Technology
100 Bureau Drive Stop 8392
Gaithersburg, MD 20899-8392
vitdqap@nist.gov