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. Author manuscript; available in PMC: 2018 Jan 17.
Published in final edited form as: Am J Kidney Dis. 2016 May;67(5):812–813. doi: 10.1053/j.ajkd.2016.02.036

Recalibration of 24,25-Dihydroxyvitamin D3 Results Based on NIST Standard Reference Material 972a

Andrew N Hoofnagle 1, Thomas J Laha 1, Ian H de Boer 1
PMCID: PMC5771237  NIHMSID: NIHMS932441  PMID: 27091017

To the Editor

We recently reported1 that lower estimated glomerular filtration rate is associated with lower circulating concentrations of 24,25-dihydroxyvitamin D3 (24,25[OH]2D3), a metabolite that is central to the catabolism and clearance of 25-hydroxyvitamin D3 (25[OH]D3). In that article, circulating 24,25(OH)2D3 and 25(OH)D3 concentrations were quantified using high-throughput mass spectrometry assays developed and validated in our laboratory.2–4 More recently, the National Institute of Standards and Technology (NIST) developed a candidate reference method procedure and used it to quantify 24,25(OH)2D3 concentration in their Standard Reference Material (SRM) 972a.5 When we used our assay to quantify 24,25(OH)2D3 in SRM 972a, we noticed that our observed concentrations were higher than those reported by NIST. Using this information, we recalibrated our assay, ran the reference materials again, and obtained concentrations that agreed with those certified for SRM 972a. From these data, we determined that the 24,25(OH)2D3 concentrations published in our report1 should be divided by a factor of 2.0 to compare our data with those generated in other laboratories for which results are calibrated to SRM 972a. This calibration does not affect the conclusions of our article, including the association of estimated glomerular filtration rate with circulating 24,25(OH)2D3 concentration or the correlations of demographic factors, clinical parameters, and regulatory hormones with 24,25(OH)2D3 concentration. Our experience is a testament to the importance of standardization programs in the proper interpretation and comparison of data from many laboratories over time.

Acknowledgments

Support: The work reported here was supported in part by grants R01DK099199, R01DK088762, R01HL096875, and P30DK035816 from the National Institutes of Health.

Financial Disclosure: The authors declare that they have no other relevant financial interests.

Peer Review: Evaluated by a Co-Editor and the Editor-in-Chief.

References

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