We retrospectively reviewed serum 25-hydroxy vitamin D (25(OH)D) test results from an adult Korean population visiting local clinics and hospitals between July 2017 and December 2021 to gather recent information on the prevalence of vitamin D deficiency. The prevalence of vitamin D deficiency status was investigated according to criteria offered by various clinical guidelines. During the study period, 180,289 subjects (29,658 men and 150,631 women) were tested for 25(OH)D. The overall prevalence rates of vitamin D deficiency status based on 25(OH)D level were as follows: 0.4% for <5 ng/mL, 12.5% for <10 ng/mL, 20.6% for <12 ng/mL, 49.4% for <20 ng/mL, and <75.3% for <30 ng/mL. Women tested their 25(OH)D level more frequently than men, and the overall prevalence of 25(OH)D < 10 ng/mL was higher among women than men, while that of 25(OH)D <30 ng/mL was lower among women than men. Among age groups, the prevalence of 25(OH)D <30 ng/mL was higher in younger patients (20s–40s, 79.6–85.5%) than older ones (≥50 years, 62.6–69.2%). The overall prevalence of vitamin D deficiency decreased over time from 2018 to 2021. Future studies are needed to clarify the clinical impact of this change.

Chae H, et al. Ann Lab Med. 2019 Sep;39(5):447-453. https://doi.org/10.3343/alm.2019.39.5.447

Sung-Eun Cho, M.D., Jungsun Han, M.S., Juyoung You, M.S., Jun Hyung Lee, M.D., Ahram Yi, M.D., Sang Gon Lee, M.D., and Eun Hee Lee, M.D.. Ann Lab Med -0001;0:. https://doi.org/10.3343/alm.2024.0072

Vitamin D (vit-D) deficiency is highly prevalent in the Korean population, highlighting the need for accurate measurements. In this study, the interferences by endogenous and cross-reactive substances were compared between routine vit-D immunoassays and mass spectrometry (MS) methods. Two MS methods and 4 immunoassays from different manufacturers (Abbott, Beckman Coulter, Roche, Siemens) were compared. Residual samples that were icteric, lipemic, hemolyzed, high in rheumatoid factor, from myeloma patients, or patients undergoing hemodialysis were collected. Also, 4 levels of National Institute of Standards and Technology (NIST) Standard Reference Material 972a, and 12 samples serially spiked with 3-epi-25-OH-D₃ were prepared. Significant interferences were observed in hemolytic (Roche), icteric (Beckman and Siemens) and lipemic samples (all 4 immunoassays). Level 4 NIST material and 3-epi-25-OH-D₃-spiked samples induced significant cross-reactivity, yielding higher total vit-D measurements in non-epimer-separating MS methods, and both the Beckman and Roche immunoassays. Most observed interferences were consistent with manufacturers’ claims, but overall improvement of immunoassay bias limits is required. Awareness of potential interference is important to increase the accuracy of vit-D measurements. Moreover, care is due when interpreting vit-D results of newborns, infants and less commonly, pregnant women, who are known to have physiologically high levels of the highly cross-reactive 3-epi-25-OH-D₃.

Background: The liquid chromatography–tandem mass spectrometry method (LC–MS/MS) identified an epimeric form of 25‐hydroxyvitamin D₃ (3‐epi‐25‐OH‐D₃) concentrations. For the first time, the 3‐epi‐25‐OH‐D₃ was included in the Korea National Health and Nutrition Examination Survey (KNHANES) IX (from 2022 to 2024). In this study, we evaluated the results of 3‐epi‐25‐OH‐D₃ in KNHANES IX to determine its clinical status in Korea.Methods: We measured 3‐epi‐OH‐D₃, 25‐OH‐D₃, and 25‐OH‐D₂ concentrations using an Ultra Performance (UP) LC–MS/MS, and assessed the differences in concentration ranges based on gender and age among participants in this national project.Results: The concentration range of 3‐epi‐25‐OH‐D₃ among 11,744 Korean participants (5193 male and 6551 female, aged 10–80 with a median age of 53) was 0.50 (lower limit of quantification) to 15.66 ng/mL, with a mean ± SD of 1.15 ± 0.85 ng/mL. The 3‐epi‐25‐OH‐D₃ concentration was not significantly different between genders. The concentrations of 25‐OH‐D metabolites were different across age groups. There was a highly significant correlation between 3‐epi‐25‐OH‐D₃ and 25‐OH‐D₃ concentrations (r = 0.77, R² = 0.5911, slope = 0.0579, p < 0.0001). The minimum and maximum of % 3‐epi‐25‐OH‐D₃ were 1.33% and 23.94%, respectively. The % 3‐epi‐25‐OH‐D₃ was highest in the highest quartile (Q4) of the total 25‐OH‐D₃ concentration (p < 0.0001).Conclusions: This is the first large‐scale study of 3‐epi‐25‐OH‐D₃ concentrations in the Korean population. Accurate measurement of 3‐epi‐25‐OH‐D₃ is necessary for the reliable results of vitamin D metabolites in KNHANES.

Cho SE, et al. Lab Med Online. 2015 Oct;5(4):196-203. http://dx.doi.org/10.3343/lmo.2015.5.4.196