Study Vitamin D in Healthy Individuals

1. Obtain matched serum and plasma specimens collected from a minimum of 50 healthy subjects in two geographic areas. Specimens will be used to determine a reference range for a vitamin D assay, used as an aid in the assessment of vitamin D sufficiency in adults. 2. Obtain serum specimens collected from a minimum of an additional 450 healthy subjects in two geographic areas. Specimens will be used to determine a reference range for a vitamin D assay, used as an aid in the assessment of vitamin D sufficiency in adults. 3. To store any remaining specimens for use in future vitamin D assay development and to evaluate as yet undetermined assays for the development of IVDs, including additional vitamin D assays