Evaluating vitamin D status in Chinese pre‐school children using dried blood spots coupled with liquid chromatograph coupled with mass spectrometer

Aim Vitamin D is an essential micronutrient for multiple physiological processes, and its deficiency remains a world‐wide public health problem that cannot be ignored. Dried blood spot (DBS) is a convenient tool in large‐scale epidemiological studies, but its application in evaluating vitamin D status in Chinese population is still scarce. Herein, we aimed to determine the vitamin D status in Chinese pre‐school children using DBS coupled with LC‐MS/MS method. Methods We first developed a sensitive and reliable method for the determination of 25‐hydroxyvitamin D (25(OH)D) in DBS samples using an ultra‐high‐performance liquid chromatograph coupled with triple quadrupole mass spectrometer (UHPLC‐QQQ‐MS/MS). Next, we conducted a pilot study to compare the 25(OH)D concentration in DBS and serum samples. Finally, the assay method was used to evaluate vitamin D status in Chinese pre‐school children. Results The present method was validated to be reliable and robust for the determination of 25(OH)D in DBS samples. Comparable consistency was observed between the 25(OH)D concentration in DBS and serum samples. A total of 3826 DBS samples collected from children aged 1–7 years were determined. The median concentration of 25(OH)D was 19.57 ng/mL (interquartile range 14.73–24.36 ng/mL), and decreased from 1 to 7 years of age. In addition, 13.51% of male children and 15.12% female children are found to be deficient in 25(OH)D. Conclusions DBS coupled with LC‐MS/MS is a feasible strategy to evaluate vitamin D status in epidemiological studies. And vitamin D deficiency remains a common health problem in Chinese pre‐school children.