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

## TL;DR

This study compares vitamin D levels measured in dried blood spots and plasma among Indian adults, finding strong agreement between the two methods.

## Contribution

The study demonstrates that dried blood spots can reliably measure vitamin D levels in Indian adults, offering a cost-effective alternative to plasma testing.

## Key findings

- 25(OH)D3 concentrations in dried blood spots and plasma were highly correlated (Pearson’s correlation = 0.976).
- DBS measurements were on average 6% lower than plasma measurements across the observed vitamin D distribution.
- The study supports the use of dried blood spots for vitamin D assessment in large-scale epidemiologic studies.

## Abstract

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.