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Vitamin D Standardization Program (VDSP)

 


VDSP News is a free electronic publication that provides updates on the activities of the Vitamin D Standardization Program (VDSP) and related information. VDSP News is sent out 4 to 6 times a year by email. Dr. Christopher Sempos, VDSP Coordinator at the NIH Office of Dietary Supplements, is the editor of VDSP News. He welcomes you to submit questions and suggestions about the program at VDSP@mail.nih.gov.

 

To receive this publication by email, send your request to subscribe to VDSP@mail.nih.gov.

All past issues of VDSP News are available here on the ODS website.

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VDSP News Number 11  March 2018

Message from Dr. Chris Sempos, VDSP Coordinator
Dear Colleagues,

My NIH/ODS consultancy will end on 31 March 2018 and the Vitamin D Standardization Program (VDSP) is moving with me and will continue its work.*  I would like to thank NIH and Dr. Paul Coates for many years of generous support.

The VDSP efforts to standardize the measurement of 25-hydroxyvitamin D [25(OH)D] in both clinical and research laboratories are in a critical phase.  Moreover, VDSP efforts to standardize the measurement of 24,25(OH)2D3, vitamin D binding protein (DBP), 1,25(OH)2D3, Parathyroid Hormone and Free 25(OH)D are just beginning.
Next steps:
  1. Continued collaboration with IFCC, CAP and DEQAS on standardization issues related to 25(OH)D and 24,25(OH)2D3 in both clinical and research laboratories;
  2. Work will continue to publish results from the VDSP Commutability 2 and Interlaboratory Comparison 2 Studies
  3. 2018 IFCC Vitamin D Working Group will evaluate updating VDSP performance criteria.
  4. NIST will continue work on development of RMP’s for Vitamin D Binding Protein, PTH and 1,25(OH)2D3.
*To contact me about VDSP, please use my personal email address: semposch@gmail.com

Recent VDSP Publications: 
Carter GD, Berry J, Durazo-Arvizu R, Gunter E, Jones G, Jones J, Makin HLJ, Pattni P, Sempos CT, Twomey P, Williams EL, Wise SA.  Hydroxyvitamin D assays: An historical perspective from DEQAS. J Steroid Biochem Mol Biol. 2018 Mar;177:30-35. PMID: 28734989.  https://www.ncbi.nlm.nih.gov/pubmed/28734989external link disclaimer
 
Binkley N, Dawson-Hughes B, Durazo-Arvizu R, Thamm M, Tian L, Merkel JM, Jones JC, Carter GD, Sempos CT.  Vitamin D measurement standardization: The way out of the chaos.  J Steroid Biochem Mol Biol. 2017 Oct;173:117-121. PMID: 27979577 https://www.ncbi.nlm.nih.gov/pubmed/27979577external link disclaimer
 
Wise SA, Tai SS, Burdette CQ, Camara JE, Bedner M, Lippa KA, Nelson MA, Nalin F, Phinney KW, Sander LC, Betz JM, Sempos CT, Coates PM.  Role of the National Institute of Standards and Technology (NIST) in Support of the Vitamin D Initiative of the National Institutes of Health, Office of Dietary Supplements. J AOAC Int. 2017 Sep 1;100(5):1260-1276. PMID: 28863788. https://www.ncbi.nlm.nih.gov/pubmed/28863788external link disclaimer

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VDSP News Number 10 November 2017

Two Upcoming VDSP Events
VDSP Presentation at 8th annual Clinical Diagnostics & Research Online Conference
November 9, 2017 at 10:30 am PST (1:30 pm EST)
 
“Serum 23-hydroxyvitamin D Assay Standardization in Clinical and Research Laboratories,” a presentation about VDSP by Dr. Chris Sempos, will be available as part of the 8th annual Clinical Diagnostics & Research free online conference produced by LabRoots. This is the link to the November 9th event: https://www.labroots.com/ms/virtual-event/clinical-diagnostics-researchexternal link disclaimer
  
Onsite Meeting and Webinar: Vitamin D Standardization Program (VDSP): The Road Ahead*
November 28, 29, & 30, 2017
National Institutes of Health (NIH), Rockville, Maryland, US
The focus of this 2.5 day meeting will be to assess the achievements of the Vitamin D Standardization Program (VDSP) based on input from the program’s stakeholders. Future plans will be discussed including an evaluation of VDSP performance criteria for 25(OH)D and the promotion of the standardization of 24,25(OH)2D3, and vitamin D binding protein as well as the development of a rickets registry. The meeting, which will be available via webinar, is sponsored by the NIH Office of Dietary Supplements. 
 
Registration: Go to the meeting website for the agenda and registration details:
https://events-support.com/events/VDSP_The_Road_Aheadexternal link disclaimer
Use Login:     VDSP     
Password:     VDSP
 *Registration for onsite and webinar attendance is required.

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VDSP News Number 9 September 2017
  
Vitamin D Standardization Program (VDSP): The Road Ahead
Meeting and Webinar Registration Now Open*
 
Dates:             November 28, 29, & 30, 2017
Location:        National Institutes of Health (NIH), Rockville, Maryland, US
Overview:      The focus of this 2.5 day meeting will be to assess the achievements of the Vitamin D Standardization Program (VDSP) based on input from the program’s stakeholders. Future plans will be discussed including an evaluation of VDSP performance criteria for 25(OH)D and the promotion of the standardization of 24,25(OH)2D3, and Vitamin D Binding Protein as well as the development of a rickets registry. The meeting, which will be available via webinar, is sponsored by the NIH Office of Dietary Supplements. 
 
*Registration is required and seating is limited.
 
Registration: Go to the meeting website for the agenda and registration details:
https://events-support.com/events/VDSP_The_Road_Aheadexternal link disclaimer
Login:             VDSP     
Password:     VDSP
  
VDSP Supplement in AOAC Journal
 
The VDSP is pleased to announce that the Journal of the AOAC International (J AOAC Int.) has published a special supplement on the VDSP and vitamin D in their Sept/Oct 2017 issue. The supplement, edited by Dr. Steven Brooks of Health Canada and Dr. Chris Sempos, ODS, contains an introduction and 16 papers covering numerous topics related to vitamin D and assay standardization.  The papers can be accessed online at the journal website here: http://www.ingentaconnect.com/content/aoac/jaoac/2017/00000100/00000005external link disclaimer

Special thanks to the J AOAC and especially to these individuals: 
  • Dr. Sarwar Gilani (Health Canada, retired), who had the idea for a J AOAC Int. special section on Vitamin D status.  Dr. Gilani worked on protein quality and nutrition while at Health Canada and has been a long-time member of the editorial board at the J AOAC Int. He is currently the Chair of the Editorial Board.  
  • Dr. Joseph Sherma (Professor Emeritus, Lafayette College), for taking charge of the section proposal and guiding it through the process at the J AOAC Int. Dr. Sherma is a section editor at the journal.  
  • Dr. Robert Rathbone (Iowa State University) for overseeing the project. Dr. Rathbone is the Senior Director of publications at the J AOAC Int. 
  • Ms. Jennifer Diatz, a Production Editor at the J AOAC Int.  Ms. Diatz for coordinating all the manuscript production and oversaw the day-to-day operations of the Special section. The issue would not have been possible without her daily input and guidance.

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VDSP News - No. 8  May 2017

ODIN Vitamin D Conference, Cork, Ireland, September 2017

 
Conference registration and submission of abstracts is open for the Vitamin D & Health in Europe: Current and Future Perspective, ODIN conference.  The conference will be held at University College Cork, Ireland, September 5-6, 2017.  http://www.vitamindconference.eu/page/2-home/external link disclaimer   Main contact:  Dr. Sinéad Lordan, ODIN Project Manager, Email: s.lordan@ucc.ie

VDSP Commutability Study 2 Update 
 
Study samples were shipped out from NIST in staggered sets beginning in September 2016 and continuing into early 2017. All shipments were successfully delivered in appropriate condition. Most participant data was returned by year-end 2016. Overall, 33 sets of data have been returned. We have prepared the data analysis template and have done some preliminary analysis of the data using the LC-MS/MS screening values from the University of Washington to check for any major data issues, such as the need for unit conversion. NIST is currently in the process of assigning the 25(OH)D2 and 25(OH)D3 RMP values, which will hopefully be completed in summer 2017.
 
24,25(OH)2D3 NIST SRM
 
NIST SRMs with target values for 24,25(OH)2D3 are available. Values for 24,25(OH)2D3 have been added to SRM 972a (see Certificate Table 3 https://www-s.nist.gov/srmors/certificates/972A.pdfexternal link disclaimer ) as well as SRM 2973 (see Certificate Table 2 https://www-s.nist.gov/srmors/certificates/972A.pdfexternal link disclaimer ).
 
VDSP and ODIN-Related Publications
 
NIST Publication on SRM 972a:
Development of an Improved Standard Reference Material for Vitamin D Metabolites in Human Serum.external link disclaimer
Phinney KW, Tai SS, Bedner M, Camara JE, Chia RRC, Sander LC, Sharpless KE, Wise SA, Yen JH, Schleicher RL, Chaudhary-Webb M, Maw KL, Rahmani Y, Betz JM, Merkel J, Sempos CT, Coates PM, Durazo-Arvizu RA, Sarafin K, Brooks SPJ.
Anal Chem. 2017 May 2;89(9):4907-4913. doi: 10.1021/acs.analchem.6b05168. Epub 2017 Apr 13.
PMID: 28375002  

ODIN Publications based on Standardized 25(OH)D Measurements using VDSP Methods:
The positive impact of general vitamin D food fortification policy on vitamin D status in a representative adult Finnish population: evidence from an 11-y follow-up based on standardized 25-hydroxyvitamin D data.external link disclaimer 
Jääskeläinen T, Itkonen ST, Lundqvist A, Erkkola M, Koskela T, Lakkala K, Dowling KG, Hull GL, Kröger H, Karppinen J, Kyllönen E, Härkänen T, Cashman KD, Männistö S, Lamberg-Allardt C. 
Am J Clin Nutr. 2017 May 10. pii: ajcn151415. doi: 10.3945/ajcn.116.151415. [Epub ahead of print] PMID: 28490516  
 
Improved Dietary Guidelines for Vitamin D: Application of Individual Participant Data (IPD)-Level Meta-Regression Analyses.external link disclaimer
Cashman KD, Ritz C, Kiely M, Odin Collaborators. 
Nutrients. 2017 May 8;9(5). pii: E469. doi: 10.3390/nu9050469.  PMID: 28481259  
 
Vitamin D and mortality: Individual participant data meta-analysis of standardized 25-hydroxyvitamin D in 26916 individuals from a European consortium.external link disclaimer
Gaksch M, Jorde R, Grimnes G, Joakimsen R, Schirmer H, Wilsgaard T, Mathiesen EB, Njølstad I, Løchen ML, März W, Kleber ME, Tomaschitz A, Grübler M, Eiriksdottir G, Gudmundsson EF, Harris TB, Cotch MF, Aspelund T, Gudnason V, Rutters F, Beulens JW, van 't Riet E, Nijpels G, Dekker JM, Grove-Laugesen D, Rejnmark L, Busch MA, Mensink GB, Scheidt-Nave C, Thamm M, Swart KM, Brouwer IA, Lips P, van Schoor NM, Sempos CT, Durazo-Arvizu RA, Škrabáková Z, Dowling KG, Cashman KD, Kiely M, Pilz S.
PLoS One. 2017 Feb 16;12(2):e0170791. doi: 10.1371/journal.pone.0170791. eCollection 2017. PMID: 28207791  
 
Standardizing serum 25-hydroxyvitamin D data from four Nordic population samples using the Vitamin D Standardization Program protocols: Shedding new light on vitamin D status in Nordic individuals. external link disclaimer Cashman KD, Dowling KG,  Škrabáková Z, Kiely M, Lamberg-Allardt C, Durazo-Arvizu RA, Sempos CT, Koskinen S, Lundqvist A, Sundvall J, Linneberg A, Thuesen B, Husemoen LL, Meyer HE, Holvik K, Grønborg IM, Tetens I, Andersen R.
Scand J Clin Lab Invest. 2015 Nov;75(7):549-61. doi: 10.3109/00365513.2015.1057898.
PMID: 26305421 

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VDSP News - No. 7  March 2016

Data from the ODIN Project: Vitamin D Deficiency is Widespread across Europe
 
The European Commission-funded ODIN vitamin D project (www.odin-vitd.eu/external link disclaimer) recently reported in the American Journal of Clinical Nutrition that the prevalence of vitamin D deficiency [serum 25(OH)D <30 nmol/L] in Europe is 13% -- that is, one in every eight individuals (article citation #1 below). Furthermore, up to 40% of individuals have serum 25(OH)D levels that are not sufficient to support good bone health (<50 nmol/L), according to the results of the ODIN project, co-coordinated by Professors Kevin Cashman and Mairead Kiely at the Cork Centre for Vitamin D and Nutrition Research in University College Cork.
 
Knowledge of prevalence of vitamin D deficiency in European populations, and relevant subgroups, is critical not only for quantifying the size of this public health problem but also for devising strategies to bring about its prevention. Making comparisons on the prevalence estimates across different countries is problematic because of method-related differences in serum 25(OH)D estimates. A key aim of the ODIN project was to apply the approaches devised by the Vitamin D Standardization Program to data from 18 European studies of children, teenagers, adults, and elderly, including a total of 55,844 individuals, and spread from as southerly as Crete (35oN) to as northerly as Tromsø, Norway (69oN). This allowed for more valid comparisons of vitamin D status across European studies and a more accurate overall estimate of the prevalence of vitamin D deficiency for Europe. 
 
This first availability of European-wide information on vitamin D status using standardized 25(OH)D data is critically important for public health authorities across Europe. The ODIN project is developing food-based strategies to prevent vitamin D deficiency in Europe.  
 
ODIN Contacts:   k.cashman@ucc.ie and m.kiely@ucc.ie

Recent VDSP and VDSP-Related Publications

Vitamin D deficiency in Europe: pandemic?external link disclaimer
Cashman KD, Dowling KG, Škrabáková Z, Gonzalez-Gross M, Valtueña J, De Henauw S, Moreno L, Damsgaard CT, Michaelsen KF, Mølgaard C, Jorde R, Grimnes G, Moschonis G, Mavrogianni C, Manios Y, Thamm M, Mensink GB, Rabenberg M, Busch MA, Cox L, Meadows S, Goldberg G, Prentice A, Dekker JM, Nijpels G, Pilz S, Swart KM, van Schoor NM, Lips P, Eiriksdottir G, Gudnason V, Cotch MF, Koskinen S, Lamberg-Allardt C, Durazo-Arvizu RA, Sempos CT, Kiely M.
Am J Clin Nutr 2016;Feb 10. pii: ajcn120873. [Epub ahead of print]
PMID: 26864360

The ODIN project: Development of food-based approaches for prevention of vitamin D deficiency throughout lifeexternal link disclaimer
Kiely M, Cashman KD.
Nutrition Bulletin 2015;40:235-246.

Standardization of vitamin D assays: The past and present dilemma for vitamin D research
Sempos CT.
Standardy Medycne 2015;12:805-809.
 

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VDSP News - No. 6  January 2016

Update on VDSP Commutability Study 2

The National Institute of Standards and Technology (NIST) has received all 50 single donor serum samples required for the VDSP Commutability Study 2 and will begin assembling sample sets in preparation for shipping to study participants (estimated March 2016).  NIST will also begin measurements of vitamin D metabolites in all commutability samples, including NIST SRMs, CAP, and DEQAS samples.  Participants will be updated as details of shipping and measurement protocols are finalized.

Values for 24R,25-dihydroxyvitamin D3 added to SRM 972a
NIST recently developed a candidate reference measurement procedure (RMP) based on LC-MS/MS for the determination of 24R,25-dihydroxyvitamin D3 in human serum, which was published in Analytical Chemistry (Susan S.-C. Tai and Michael A. Nelson, 87:7964-7970, 2015).  This candidate RMP was used to assign values for 24R,25-dihydroxyvitamin D3 in SRM 972a Vitamin D Metabolites in Frozen Human Serum.  The Certificate of Analysis for SRM 972a was updated in September 2015 with reference values for 24R,25-dihydroxyvitamin D3 in all four levels ranging from 1.41 ± 0.05 ng/mL (3.39 ± 0.12 nmol/L) to 2.66 ± 0.10 ng/mL (6.38 ± 0.23 nmol/L).  SRM 972a is available from NIST at www.nist.gov/srmexternal link disclaimer.

DEQAS
The VDSP works closely with DEQAS, the international quality assessment scheme for vitamin D metabolites. Five human serum samples are distributed quarterly and the scheme has over 1000 participants in 58 countries. Four samples are used to assess assay performance and the fifth for investigative purposes, e.g. looking at the effect of other serum constituents on the accuracy of results. 
CAP-accredited laboratories in the US and Canada may use DEQAS as their primary proficiency testing scheme for 25-hydroxyvitamin D (25-OHD).  DEQAS is accuracy based with target values for 25-OHD3 and 25-OHD2 assigned to all samples by the NIST Reference Measurement Procedure. The NIST LC-MS/MS method is also used to establish values for 3-epi-25-OHD3 , which should be of interest to users of chromatographic assays. There is a separate scheme for 1,25(OH)2D and in April 2015, a pilot scheme for 24,25(OH)2D was introduced which currently has 6 participants. Further information is available on www.deqas.org or by e-mail: administrator@deqas.org 

Recent Publications: 

25-Hydroxyvitamin D assays: Potential interference from other circulating vitamin D metabolites.external link disclaimer
Carter GD, Jones JC, Shannon J, Walker E, Jones G, Kaufmann M, Sempos C.
J Steroid Biochem Mol Biol. 2015 Dec 21.  doi: 10.1016/j.jsbmb.2015.12.018. [Epub ahead of print] 
PMID: 26718874

Developing vitamin D dietary guidelines and the lack of 25-hydroxyvitamin D assay standardization: The ever-present past.external link disclaimer
Sempos CT, Durazo-Arvizu RA, Binkley N, Jones J, Merkel JM, Carter GD.
J Steroid Biochem Mol Biol. 2015 Aug 28.  doi: 10.1016/j.jsbmb.2015.08.027. [Epub ahead of print] 
 

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VDSP News - No. 5 October 2015

Update on VDSP Commutability Study 2
Thirty-six clinical/research and commercial manufacturers’ laboratories have volunteered to participate in the VDSP Commutability Study 2. To date NIST has received 16 of the 50 single donor serum samples needed for the study. NIST anticipates receiving the remaining 34 samples by the end of October. 

VDSP Progress
The VDSP is making good progress in promoting the standardization of commercially developed assays. CDC, through their Vitamin D Standardization Certification Program, has certified, as of May 2015, 19 laboratories around the world as being standardized or traceable to the NIST and Ghent Reference Measurement Procedures: http://www.cdc.gov/labstandards/hs.htmlexternal link disclaimer. This list includes assay platforms marketed by assay manufacturers, commercial and clinical laboratories, and research laboratories. Consult the list regularly to get the latest information.
Note to participants in CAP ABVD and/or DEQAS: if you use a commercial assay that has been standardized and notice irregularities in your results, please be sure to contact your technical representative immediately to see if your assay platform needs “fine tuning.”

Importance of Assay Standardization in Vitamin D Research
An important problem in vitamin D research is the lack of standardized 25(OH)D results. VDSP is therefore launching an international effort to promote the identification and standardization of 25(OH)D measurements from key studies conducted in the past. Two recently published papers (citation and links below) emphasize its importance. In the Danish health survey the percentage of vitamin D deficiency, i.e. < 30 nmol/L, decreased by 21.5% after standardization while the percentage with values < 40 nmol/L in the Canadian Health Measures Survey increased from 16% – 19%. Lack of standardization will continue to confound the development of clinical and public health guidelines for vitamin D without a concerted effort to standardize 25(OH)D measurements from key studies conducted in the past.

Recent VDSP Publications

Standardizing serum 25-hydroxyvitamin D data from four Nordic population samples using the Vitamin D Standardization Program protocols: Shedding new light on vitamin D status in Nordic individualsexternal link disclaimer
Cashman KD, Dowling KG, Škrabáková Z, Kiely M, Lamberg-Allardt C, Durazo-Arvizu RA, Sempos CT, Koskinen S, Lundqvist A, Sundvall J, Linneberg A, Thuesen B, Husemoen LL, Meyer HE, Holvik K, Grønborg IM, Tetens I, Andersen R.
Scand J Clin Lab Invest. 2015 Nov;75(7):549-61. doi: 10.3109/00365513.2015.1057898.

Standardizing 25-hydroxyvitamin D values from the Canadian Health Measures Surveyexternal link disclaimer
Sarafin K, Durazo-Arvizu R, Tian L, Phinney KW, Tai S, Camara JE, Merkel J, Green E, Sempos CT, Brooks SP.
Am J Clin Nutr. 2015 Sep 30. pii: ajcn103689. [Epub ahead of print]
 

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VDSP News - No. 4 March 2015

VDSP Vitamin D Commutability Study 2
The VDSP Commutability Study 2 is moving forward. If you would like to recieve a pdf document/slide set summarizing current plans for the study including the objectives, protocol, and timeline please contact us.  We will continue to keep you up-to-date as our plans progress. Please let us know by email (VDSP@mail.nih.gov) if you are interested in participating in this study and feel free to share this information with any colleagues you think might be interested in participating.  

Recent VDSP Publication
Significance of serum 24,25-dihydroxyvitamin D in the assessment of vitamin D status: a double-edged sword?external link disclaimer
Clinical Chemistry.  2015 Feb 20. pii: clinchem.2014.234955. [Epub ahead of print]
Kevin D. Cashman, Aoife Hayes, Karen Galvin, Joyce Merkel, Glenville Jones, Martin Kaufmann, Andrew N. Hoofnagle, Graham D. Carter, Ramon A. Durazo-Arvizu and Christopher T. Sempos

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VDSP News - No. 3 January 2015

Invitation to Comment on ODS Progress Report

As subscribers to VDSP News, thank you for your interest in the work of the NIH Office of Dietary Supplements (ODS) on vitamin D. We now invite you to take part in the ODS strategic planning process by reviewing the Strategic Plan 2010-2014 Progress Report, a key component of which is the Vitamin D Initiative (Section B1) which includes the Vitamin D Standardization Program (VDSP).
 
We welcome comments and suggestions from you and your colleagues concerning VDSP and any of the other programs described in the Report as we develop a new strategic plan for the years 2015-2019.  We request guidance on important issues such as:
·         Are current VDSP strategic goals adequate?
·         Is the VDSP meeting its stakeholders' needs?
·         Should any of VDSP's current programs or activities be given higher (or lower) priority?
          Are any new programs needed?
·         How can VDSP more effectively provide useful information to the VDSP participants?
 
Interested individuals and organizations should submit their comments to ODSplan@od.nih.gov by midnight, March 6, 2015. We look forward to your comments. 

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VDSP News - No. 2 December 2014

Vitamin D Conference Video Cast Available 
A recording of the December 2–3, 2014, Vitamin D: Moving Toward Evidence-based Decision Making in Primary Care Conference is now available on the NIH Past Events Websiteexternal link disclaimer. Session 5 on Day 2 focused on laboratory measurement of serum 25(OH)D and featured a presentations by Dr. Andrew Hoofnagle and a panel discussion.  In both, opinions were given on the best assay methodology to be used in the clinical setting. 

To be clear, the VDSP does not have a preferred assay methodology.  VDSP policy is that any 25(OH)D assay regardless of the approach, e.g. immunoassay or HPLC or LC-MS/MS, that can demonstrate traceability to NIST and Ghent reference measurement procedures by meeting the VDSP performance guidelines of a CV ≤ 10% and a Mean Bias ≤ 5% is satisfactory. The VDSP position on vitamin D laboratory assays is that we will  work with any and all assay manufacturers,  regardless of the approach they have taken, to help them develop a vitamin D assay that can meet the VDSP performance guidelines and then let the market choose.

Below are the direct links to each day of the conference recording.
·         Day 1 Recordingexternal link disclaimer
·         Day 2 Recordingexternal link disclaimer 
 
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VDSP News - No. 1 October 2014

VDSP Commutability Study
VDSP is planning a new commutability study. It will be led by Dr. Johanna Camara of the National Institute of Standards and Technology (NIST) and will include as many assay systems as possible from commercial assay manufacturers and laboratory developed assays. Please let us know (VDSP@mail.nih.gov ) if you would like more details and if you are interested in participating in this study. We plan to send out single donor serum samples along with test samples to participating laboratories in June 2015.
 
New Calibration Solution for 25-Hydroxyvitamin D 
A new calibration solution Standard Reference Material (SRM) for 25-hydroxyvitamin D will be released by the National Institute of Standards and Technology (NIST) in November, 2014.  SRM 2972a 25-Hydroxyvitamin D Calibration Solutions is an expanded version of and replacement for SRM 2972 25-Hydroxyvitamin D2 and D3 Calibration Solutions. It consists of five 2-mL ampoules of each of four solutions:
 
25-Hydroxyvitamin D3 Calibrant in Ethanol Level 1 (nominally 400 ng/g)
25-Hydroxyvitamin D3 Calibrant in Ethanol Level 2 (nominally 800 ng/g)
25-Hydroxyvitamin D2 Calibrant in Ethanol (nominally 300 ng/g)
3-Epi-25-hydroxyvitamin D3 Calibrant in Ethanol (nominally 300 ng/g)
 
For the Certificate of Analysis and for information on how to purchase SRM 2972a, please see the NIST SRM website at http://www.nist.gov/srm/index.cfmexternal link disclaimer.
 
Upcoming NIH Conference 
The NIH Office of Dietary Supplements (ODS) is sponsoring a 2-day conference titled Vitamin D: Moving Toward Evidence-based Decision Making in Primary Care on December 2-3, 2014 on the NIH Campus (Bethesda, MD, USA). Available via webinar, this conference designed especially for researchers, clinical educators, those who develop clinical recommendations, and health care providers. The conference program includes discussion of the laboratory measurement of serum 25(OH)D concentration. For more information and to register: https://events-support.com/events/Vitamin_D_Primary_Careexternal link disclaimer
 
Recent VDSP Publications
Standardizing vitamin D assays: the way forward.external link disclaimer
Journal of Bone and Mineral Research. 2014 Aug;29(8):1709-1714.
Neil Binkley, Christopher T. Sempos; Vitamin D Standardization Program (VDSP).
 
Assessing vitamin D status: time for a rethink?external link disclaimer
Clinical Chemistry. 2014 Jun;60(6):809-811.
Graham D. Carter, Karen W. Phinney. 
 
The estimation of calibration equations for variables with heteroscedastic measurement errors.external link disclaimer
Statistics in Medicine. 2014 Nov 9;33(25):4420-4436.
Lu Tian, Ramon A. Durazo-Arvizu, Gary Myers, Steve Brooks, Kurtis Sarafin, Christopher T. Sempos.