Background and objectives: Vitamin D deficiency is a significant public health concern globally including Bangladesh. Currently, Bangladeshi population is being evaluated for vitamin D status using reference interval derived from western studies. Reference interval derived from western populations may not reflect the actual status of vitamin D status of Bangladeshi population due to differences in sun exposure, ethnicity and dietary habits. Therefore, this study aimed to find out the reference intervals and the lower cutoff value of serum 25-hydroxyvitamin D 25(OH)D deficiency in healthy Bangladeshi adult population. Materials and methods: This cross-sectional study was conducted involving two population groups. Group-1 comprised of adequately sun exposed healthy coastal fishermen and Group-2 included healthy urban dwellers. Group-1 represented an ideal population for assessing the reference serum vitamin D level while Group-2 population was used to detect the cut-off value of vitamin D deficiency level in adult Bangladeshi population. Chemiluminescent microparticle immunoassay (CMIA) was used to estimate serum 25(OH) D. Serum iPTH and other biochemical parameters were analysed by standard methods. The reference interval of vitamin D was determined according to Clinical and Laboratory Standards Institute (CLSI) Guidelines C28-A3. The lower cut-off value of vitamin D deficiency level was determined by detecting deflection point of parathyroid hormone (PTH) level compared to serum 25(OH)D level. Results: Total 125 and 371 individuals were enrolled in Group 1 and Group 2 respectively. The mean age of the Group-1 and 2 study populations were 37.98±11.61 and 44.19 ± 11.48 years respectively. The mean serum vitamin D levels of Group-1 and 2 study population were 27.36±7.27 ng/ml (95% CI: 26.08, 28.65) and 21.53±15.98 ng/ml (95% CI: 19.9, 23.16) respectively. Serum reference interval of vitamin D of healthy adults (Group-1) was found as 15.88 to 45.27 ng/ml. The cut-off value for vitamin D deficiency in Group-2 adult population was 12.16 ng/ml (95% CI: 11.04, 13.28) as depicted by first upward deflection of serum iPTH when serum 25(OH)D level fell below 12.16 ng/ml. Conclusion: The findings suggest that current Western-based vitamin D reference intervals may not be appropriate for the Bangladeshi population. The results of our study would help the clinicians and policymakers in developing strategies to address vitamin D deficiency in Bangladesh. January 2026; Vol. 20(1):006. DOI: https://doi.org/10.55010/imcjms.20.006 *Correspondence: Wasim Md Mohosin Ul Haque, Department of Nephrology, Bangladesh Institute of Research and Rehabilitation in Diabetes, Endocrine and Metabolic Disorders, Dhaka, Bangladesh. E-mail: wmmhaque@live.com. © 2026 The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License(CC BY 4.0).
Haque et al. (Mon,) studied this question.