A Quantitative Point-of-Need Assay for the Assessment of Vitamin D3 Deficiency
Sci Rep. 2017; 7: 14142. doi: 10.1038/s41598-017-13044-5
S. Vemulapati,1 E. Rey,1 D. O’Dell,2 S. Mehta, smehta@cornell.edu) or D.E. de54@cornell.edu. 3,4 and D. Erickson smehta@cornell.edu
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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 D3 (25(OH)D3), 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)D3 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)D3, we also demonstrate a novel elution buffer that separates 25(OH)D3 from its binding protein in situ, eliminating the need for sample preparation. In human trials, the accuracy of our platform is 90.5%.