Estimation of Vitamin D Reference Range in Apparently Healthy Blood Donors: A Single-center Cross-sectional Observational Study

Background: Vitamin D deficiency (VDD) is a global concern, impacting bone health and potentially other chronic diseases.Community-based studies conducted over the past decade on apparently healthy individuals across India have reported majority of the healthy Indian population may be classified as vitamin D deficient.The Indian population might have distinct vitamin D levels, which may be different as compared to Western populations due to factors like higher melanin content in skin (reduced sunlight-based vitamin D synthesis), dietary factors, and cultural practices influencing vitamin D intake.Establishing a population-specific reference range is crucial for accurate diagnosis and management of VDD in patients with suspected VDD.Since there is a paucity of data from India, we undertook a cross-sectional observational study of vitamin D levels in apparently healthy blood donors.Materials and methods: Leftover serum samples of all apparently healthy individuals who came for blood donation were collected from the blood bank.The study was performed over a period of 6-8 months in 2024.Measurement of 25(OH)D levels was done by an automated test kit based on the principle of chemiluminescence immunoassay (CLIA) method in the biochemistry lab.Results: A total of 581 donor samples were included in the study.Vitamin D reference range in apparently healthy blood donors was calculated as 10.2-57.4ng/mL.Median and interquartile range in blood donors are 21 ng/mL (15.4-27.4).Reference range in males was 10-57.9ng/mL.Reference range in the urban population was 10.2-59.3ng/mL, while in the rural population, it was 9.3-43.5 ng/mL.Reference range in the population having an indoor workplace was 10.2-60 ng/mL, whereas having an outdoor workplace was 9.5-46.9ng/mL. Conclusion:The present study shows that the Indian biological reference range for vitamin D is lower than the traditionally used Western biological reference ranges.Clinical significance: Owing to its wide-ranging impact on health, the epidemic of VDD in India is likely to significantly contribute to the enormous burden on the healthcare system.The establishment of a reference range through this study can provide a comprehensive picture of the vitamin D status among blood donors.