[en] The External Quality Assessment (EQA) scheme for vitamin D metabolites (DEQAS) distributes human serum samples to laboratories across the world to assess their performance in measuring serum total 25-hydroxyvitamin D [25(OH)D], i.e. the sum of the concentrations of serum 25(OH)D2 and 25(OH)D3. In 2013 DEQAS, in collaboration with the Vitamin D Standardization Program (VDSP), became an accuracy-based EQAS when the National Institute for Standards and Technology (NIST) began assigning 25(OH)D target values to DEQAS serum samples using their Joint Committee for Traceability in Laboratory Medicine (JCTLM) approved reference measurement procedure (RMP). Historically, NIST has performed 4 determinations of 25-OHD2 and 25-OHD3 on each sample and used the mean values to calculate a single 'target value' for Total 25-OHD against which performance was judged. By definition the target values cannot be exact and each is associated with a level of uncertainty. The total uncertainty (UNIST) has two components, one from the 25(OH)D2, and 25(OH)D3 measurements and the other associated with the calibration procedure. The total combined uncertainty is calculated by adding up these uncertainties. In future, uncertainties will be attached to the target value in each DEQAS serum sample, starting with the next distribution cycle in 2019. Confidence intervals obtained using these uncertainties will allow DEQAS participants to determine if their result agrees with the NIST assigned target value. Furthermore, if the value falls within the confidence interval the laboratory's assay would be regarded as traceable, i.e. standardized, to the NIST RMP.
Disciplines :
Laboratory medicine & medical technology
Author, co-author :
Durazo-Arvizu, Ramon
Ahmed, F.
Berry, J.
Cavalier, Etienne ; Université de Liège - ULiège > Département de pharmacie > Chimie médicale
Gunter, E.
Jones, G.
Jones, J.
Sempos, C. T.
Twomey, P. J.
Williams, E. L.
Carter, G. D.
Language :
English
Title :
Estimating uncertainty of target values for DEQAS serum materials.
Publication date :
2019
Journal title :
Journal of Steroid Biochemistry and Molecular Biology
ISSN :
0960-0760
eISSN :
1879-1220
Publisher :
Elsevier, United Kingdom
Peer reviewed :
Peer Reviewed verified by ORBi
Commentary :
Copyright (c) 2019 Elsevier Ltd. All rights reserved.
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Bibliography
Burdette, C.Q., Camara, J.E., Nalin, F., Pritchett, J., Sander, L.C., Carter, G.D., Jones, J., Betz, J.M., Sempos, C.T., Wise SA: establishing an accuracy basis for the vitamin d external quality assessment scheme (DEQAS). J. AOAC Int. 100:5 (2017), 1277–1287.
Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results. NIST Technical Note 1297 https://www.nist.gov/pml/nist-technical-note-1297.
Standard Reference Material 972a, Vitamin D Metabolites in Frozen Human Serum https://www-s.nist.gov/srmors/certificates/972a.pdf.
Standard Reference Material 972, Vitamin D in Human Serum https://www-s.nist.gov/srmors/certificates/972.pdf.
Possolo, A., Toman, B., Vitamin D Standardization Program. Value Assignment and Evaluation of Uncertainty for Averages of Determinations. White Paper July 28. 2013.
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