Evaluation of Vitamin D Status in Seasonal Serum Samples
Abstract:
Introduction: Today, the measurement of vitamin D is commonly used for the diagnosis of osteoporosis and for es tablishing optimal serum levels that may help prevent various other diseases. The aim of this study was to investigate whether the season—specifically the time of year when the blood sample is collected—affects total serum vitamin D concentration in the population of the Dukagjini Plain in the Republic of Kosovo.
Materials and Methods: A retrospective study was conducted at two laboratories: the "Biolab- Zafi-F" Medical Laboratory in Peja and the "Biolab-Zafi" Polyclinic Laboratory in Klina. Serum levels of total 25-hydroxyvitamin D were analyzed in non-hospitalized patients aged over 58 years, during the period from January 1, 2022, to August 31, 2024. Vitamin D measurements were performed using the cobas e 411 analyzer, a fully automated system based on ElectroChemiLuminescence (ECL) technology.
Results: A total of 863 outpatient serum samples were analyzed. Vitamin D concentrations were consistently lower in samples collected during the winter season compared to the other three seasons. Multivariate analysis revealed that total vitamin D concentration was independently associated with sex and season of sample collection, but not with patient age.
Conclusion: The season in which blood samples are collected should be considered an important preanalytical variable in vitamin D testing. The amount of vitamin D synthesized during the summer appears sufficient to maintain serum levels above 45–55 nmol/L throughout the rest of the year.
