Article: Vemulapati, S; Rey, E; O’Dell, D; Mehta, S; Erickson, D; “A Quantitative Point-of-Need Assay for the Assessment of Vitamin D-3 Deficiency”, Scientific Reports, 7
Abstract: Vitamin D is necessary for the healthy growth and development of bone and muscle. Vitamin D deficiency, which is present in 42% of the US population, is often undiagnosed as symptoms may not manifest for several years and long-term deficiency has been linked to osteoporosis, diabetes and cancer. Currently the majority of vitamin D testing is performed in large-scale commercial laboratories which have high operational costs and long times-to-result. Development of a low-cost point-of-need assay could be transformative to deficiency analysis in limited-resource settings. The best biomarker of vitamin D status, 25hydroxyvitamin D-3 (25(OH)D-3), however, is particularly challenging to measure in such a format due to complexities involved in sample preparation, including the need to separate the marker from its binding protein. Here we present a rapid diagnostic test for the accurate, quantitative assessment of 25(OH)D-3 in finger-stick blood. The assay is accompanied by a smartphone-assisted portable imaging device that can autonomously perform the necessary image processing. To achieve accurate quantification of 25(OH)D-3, we also demonstrate a novel elution buffer that separates 25(OH) D-3 from its binding protein in situ, eliminating the need for sample preparation. In human trials, the accuracy of our platform is 90.5%.
Funding Acknowledgement: National Science Foundation 
Funding Text: D.E. and S.M. acknowledge primary funding support for this effort from the National Science Foundation Award 1430092. The authors would also like to thank Olga Malyshev of the College of Human Ecology at Cornell for conducting tandem mass spectrometry diagnostics. The authors also thank Erica Bender for performing finger pricks and venipunctures for the human trials.