Quantification of 25-hydroxyvitamin D ₃ in dried blood spots as compared to plasma among Indian adults

Vitamin D may play an important role in later-life physical and cognitive health. Vitamin D status is standardly assessed in serum and plasma; however, collection, transport, and storage costs make large epidemiologic studies challenging. We assessed the agreement of 25-hydroxyvitamin D ₃ (25(OH)D ₃) quantification from dried blood spots (DBS) as compared to standard plasma assessment among older Indian adults.

A total of 58 adults over 45 years of age who resided in Pune, India were enrolled in the study from July 2020 to June 2021. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to assess 25(OH)D ₃ concentrations in paired plasma and DBS samples.

Plasma and DBS 25(OH)D ₃ concentrations were highly correlated (Pearson's correlation = 0.976). The median 25(OH)D ₃ concentration of the study population assessed by plasma was 14.6 ng/mL (Q1=12.0, Q3= 18.1) while the median concentration assessed in DBS was 12.8 ng/mL (Q1=11.0, Q3= 16.6). 25(OH)D ₃ concentrations measured from DBS were on average 6% (95% CI: 2-13%) lower than concentrations assessed by plasma across the observed 25(OH)D ₃ distribution.

We found good agreement between 25(OH)D ₃ quantification between DBS and plasma and our findings indicate that DBS can be used in epidemiologic studies of vitamin D among Indian adults.