Can dried blood spots be used to accurately measure vitamin D metabolites?

Michael J. Binks, Amy S. Bleakley, Geetha Rathnayake, Susan Pizzutto, Anne B. Chang, Brett McWhinney, Jacobus Ungerer

Research output: Contribution to journalArticlepeer-review


Background: Where conventional blood sampling is challenging, dried blood spots (DBS) provide a practical sample alternative for measuring vitamin D levels. Our study aimed to develop and evaluate a clinical pathology service-based assay suitable for measuring vitamin D in batches of DBS samples collected remote to the testing site. 

Methods: A high throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) method with derivatisation was developed to measure 25-hydroxyvitamin D metabolites (25OHD3, 25OHD2 and 3-epi-25OHD3) in DBS samples. The assay was validated using paired DBS and plasma samples from 37 healthy adults. 

Results: The assay reproducibly (<11.5% coefficient of variation) quantified 25OHD3 (range 1–300 nmol/L), 25OHD2 (range 2–300 nmol/L) and 3-epi-25OHD3 (range 1–200 nmol/L) in DBS samples. The 25OHD3 metabolite was detected in all DBS samples, 3-epi-25OHD3 in six plasma (range 2.1–6.3 nmol/L) and paired DBS samples, and 25OHD2 was not detected. Concentrations of 25OHD3 were highly correlated between paired samples: capillary DBS and venous plasma (r = 0.92), venous DBS and venous plasma (r = 0.93), and capillary DBS and venous DBS (r = 0.97). Ordinary least squares regression was used to characterise (β = 0.81) and correct the systematic bias in DBS data (compared to paired plasma). Thereafter, Bland-Altman analysis demonstrated robust agreement between sample-methods. 

Conclusion: This simple and rapid DBS-based LC-MS/MS assay accurately quantified serum vitamin D metabolites using a paired-sample ‘bridging strategy’ to correct for the inherent sample-method bias.

Original languageEnglish
Pages (from-to)70-77
Number of pages8
JournalClinica Chimica Acta
Early online date10 Mar 2021
Publication statusPublished - Jul 2021


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